Printer Friendly

Biological patterns of the argentine shortfin squid Illex argentinus in the slope trawl fishery off Brazil/Patrones biologicos del calamar argentino Illex argentinus en la pesqueria de arrastre en el talud continental de Brasil.

INTRODUCTION

Squids have long represented important bycatch components of the multispecific trawl fishery off Brazil (Costa & Haimovici, 1990; Perez & Pezzuto, 1998). On the continental shelf, loliginids have further become seasonal targets of both hand jigging and trawl fisheries, as they are densely concentrated in space and time (Perez, 2000; Martins & Perez, 2007). In recent years, however, commercial landings of the ommastrephid Argentine shortfin squid Illex argentinus (Castellanos, 1960) have been recorded in the southeastern and southern sectors of the Brazilian coast and have placed this squid among the main cephalopod resources exploited in the country (Perez et al., 2009a).

The species is distributed in the SW Atlantic from Rio de Janeiro (23[degrees]S) to southern Argentina (54[degrees]S) sustaining, on the Patagonian shelf and around the Falkland (Malvinas) Islands, one of the largest cephalopod fisheries in the world (Boyle & Rodhouse, 2005). Off Brazil, several fishing surveys conducted since the 1970s have revealed important concentrations of paralarvae, juveniles, and spawning individuals, particularly in the shelf break and slope waters of the southern coast (south of 25[degrees]S) (Haimovici & Andriguetto Fo, 1986; Haimovici & Perez, 1991; Haimovici et al., 1995, 2007, 2008). In this area, the species has also been often found in stomach contents of large predators, and it is regarded as one of the key components of both pelagic and demersal trophic chains (Santos & Haimovici, 2000; Gasalla et al., 2007).

Commercial exploitation of the Argentine shortfin squid was virtually non-existent in Brazilian waters until 2000, when foreign-chartered trawlers initiated their operations on the slope grounds south of 20[degrees]S (Perez et al., 2003, 2009b). In that year, the Portuguese trawler "Joana" landed approximately 48 ton of this species caught during one fishing trip between 26-29[degrees]S and 235-401 m isobaths (Perez et al., 2003). In 2002, the South-Korean trawler "In Sung 207" exploited the same area in winter (June-September) catching, on average, 199 kg of I. argentinus per trawling hour. After four fishing trips, this vessel landed a total of 1,400 ton, the largest catch ever recorded in Brazilian waters (Perez et al., 2009b). In total, landings of I. argentinus that year reached 2,601 ton, nearly twice the amount recorded for other squids (mostly loliginids). These catches, however, decreased to 100-400 ton in the following years, as chartered trawlers either abandoned Brazilian waters or moved to deeper areas (> 700 m). Since then, national trawlers have included I. argentinus among the targets of a developing "upper slope" (250-500 m) trawl fishery (Perez & Pezzuto, 2006; Perez et al., 2009a).

Preliminary assessments of this fishery have considered I. argentinus to be a seasonal resource with a fishing potential that has not been objectively defined but that is generally considered to be highly variable and unpredictable (Haimovici et al., 2006). The main questions regarding the biological aspects of I. argentinus commercial exploitation off Brazil, however, revolve around its complex population structure and potential connections with migrating stocks exploited off Uruguay and Argentina (Perez et al., 2003; Haimovici et al., 2006). As most ommastrephid squids, I. argentinus is a short-lived species (~1 year) that matures late in life and dies after a single and terminal spawning event (Haimovici et al., 1998). Because generations do not overlap in time, population resilience is highly dependent on recruitment and, consequently, annual abundances typically exhibit wide oscillations, as do commercial catches (Boyle & Rod house, 2005). Associated with this extreme life history pattern, ommastrephids tend to combine extended spawning seasons, long reproductive migrations, and the passive transport of offspring by surface geostrophic currents to produce both seasonal and geographic population units (stocks); this complex structure is regarded as an evolutionary strategy to minimize the risks of semelparity (O'Dor, 1998).

In the SW Atlantic, at least four stocks were distinguished from general size-at-maturity patterns: summer spawning stock (SSS), south Patagonian stock (SPS), Bonaerensis north Patagonian stock (BNS), and southern Brazil stock (SBS) (Brunetti, 1988; Haimovici et al., 1998). The latter group included the main concentrations of spawning squid found in winter months on the slope off southern Brazil (Haimovici & Perez, 1990; Santos & Haimovici, 1997). Growing biological evidence (i.e. maturation patterns, trophic relationships, the occurrence of certain parasites, statolith morphometrics), however, suggests that these squid are in fact BNS members that migrate north to spawn in Brazilian waters (Santos & Haimovici, 1997; Schwarz & Perez, 2007). Although local spawning was also observed occuring off Brazil throughout the year, winter spawning was potentially linked to recruitment off the northern Patagonian shelf through paralarval transport by the Falkland (Malvinas)-- Brazil Current system (Haimovici et al., 1995). In this context, this study analyzes biological attributes of commercial catches of the Argentine shortfin squid off southern Brazil as a descriptive approach to assess both the population structure subject to the seasonal exploitation regime and the hypothesis of a shared stock scenario.

MATERIAL AND METHODS

Biological samples of the Argentine shortfin squid were obtained from commercial catches of 25 national and seven foreign (chartered) trawlers all derived from operations in the southeastern and southern sectors of the Brazilian coast (Fig. 1) between 23[degrees]-33[degrees]S and 170-740 m depth. Samples represent two periods of the species' commercial exploitation in Brazil: 2001-2003, when both chartered and national slope trawlers operated simultaneously, and 2006-2007, when only national vessels continued to exploit I. argentinus along with other slope stocks (Table 1) (Perez & Pezzuto, 2006; Perez et al., 2009b).

Onboard observers collected samples from chartered trawlers for all fishing trips conducted principally between September 2001 and April 2003. After each positive trawl, a sample was taken from the catch and deep-frozen for posterior analysis in the laboratory ashore. Each sample had detailed information on trawl position (lat-long), date, time, and fishing effort (trawling hours). Samples from national trawlers were collected from landings at the harbors of Santa Catarina state (southern Brazil) as part of a daily fishery sampling program (Perez et al., 1998). From each landed catch, approximately 20 kg of squid were measured for their dorsal mantle length (ML) to the nearest centimeter, and a length stratified subsample was taken to the laboratory. These subsamples could not be related to individual trawls conducted during each fishing trip, but represented the entire fishing area covered by it. Information on the fishing area, effort (mean trawl duration, number of trawls per day, trip duration in days), and total catch were obtained during interviews with skippers at the time of the landings.

[FIGURE 1 OMITTED]

In the laboratory, the ML and the total body weight (BW) were recorded to the nearest millimeter and gram, respectively. After dissecting the mantle, males and females were differentiated and maturity stages were assigned according to the macroscopic scale proposed by Brunetti (1990). This scale defined seven and eight maturity stages for males and females, respectively, including: immature (stages I and II), in maturation (stage III), early maturity (stage IV), advanced maturity (stage V), spawning (stage VI for males and stages VI and VII for females), and spent (stage VII for males and stage VIII for females).

In females, the ovary and accessory organs (oviduct + nidamental glands + oviducal gland) were weighed (OW and AOW, respectively), the nidamental gland length was measured (NGL), and the gills were checked for the presence of spermatophores as signs of mating. In males, the testis and accessory organs (spermatophoric complex + Needhan's sac + penis) were weighed (TW and AOW, respectively), the testis length was measured (TL), and the Needhans's sac was examined for the presence of spermatophores. All weights were taken to the nearest 0.1 g and measurements to 0.1 mm.

Maturation in males and females was expressed numerically by three indices:

a) the Gonadosomatic index defined for males ([GSI.sub.M]) and females ([GSI.sub.F]) as:

[GSI.sub.M] = [TW + AOW/(BW - (TW + AOW))]100

[GSI.sub.F] = [OW + AOW/(BW - (OW + AOW))]100 (1)

b) the Hayashi index (HI) defined for males ([HI.sub.M]) and females ([HI.sub.F]) as

[HI.sub.M] = AOW/TW + AOW, [HI.sub.F] = AOW/OW + AOW

c) the Testis (TI) - Nidamental Gland (NGI) indices defined as

TI = TL/ML, NGI = NGL/ML

A data bank was produced in which each squid was described by its origin (sample, landing date), sex, size (ML, BW), and reproductive characteristics (maturity stage, OW, TW, AOW, GSI, HI, TI/ NGI).

Size-at-maturity was assessed from the cumulative ML frequency distribution of mature and spawning males and females (stages > IV). This distribution was linearized by the probit transformation of cumulative ML frequencies and a straight line was then fitted to the transformed frequency vs. ML class relationship using the least-squares method. Precise ML at different percentiles were then estimated by substituting the probit values in the estimated linear equation (i.e. probit 5 corresponds to 50% percentile):

[ML.sub.m] = pf - c/d (4)

where pf is the probit transformed ML cumulative frequency and c and d are the intercept and the slope of the fitted line, respectively.

Population differentiation among squid caught by commercial trawlers was explored through a multivariate Principal Component Analysis (PCA) applied separately for males and females. Variables included in this analysis involved size and reproductive attributes (BW, GSI, HI, TI/ NGI), day-of-the-year (DYR), decimal latitude (LAT), decimal longitude (LONG), and depth (DEPTH). A correlation matrix was calculated for the variables (previously standardized as a proportion of their mean) and new axes (factors) were extracted in the direction of greatest variance. These factors were linear combinations of the original variables and used to interpret the potential existence of biologically similar groups of squids and their occurrence in space and time.

RESULTS

Size structure of catches

Males and females caught during slope trawl fishing exhibited a bi-modal ML frequency distribution (Fig. 2). Males ranged from 78 to 340 mm ML, exhibiting one pronounced mode centered around 160 mm ML and a secondary mode between 220 and 240 mm ML. Females were generally larger, ranging from 91 to 395 mm ML. A main modal group was formed around 180 mm ML and a less pronounced one between 280-320 mm ML (Fig. 2, Table 1). The overall size structures remained practically unchanged as the catches by the chartered and national trawlers in 2001-2007 were examined separately, although larger females were found in the former (Fig. 2).

During the early exploitation period (2001-2003), the size structure of the chartered fleet catches varied with the season, latitude, and depth of commercial operations (Figs. 3 and 4). Large males (ML > 200 mm) dominated catches obtained in winter (July-September) south of 28[degrees]S, between 350-540 m depth (Fig. 3). During the rest of the year, catches were generally unimodal, concentrating on individuals between 100-250 mm ML that originated north of 28[degrees]S and on the upper slope (< 400 m depth). In females, the patterns observed were virtually the same (Fig. 4), with an uniform group of individuals (100-250 mm ML long) dominating the catches throughout the year, except for winter months when a distinct group of large females was caught in southern (south of 28[degrees]S) and deeper (> 350 m) areas.

Slope trawling between 2006-2007, as conducted by the national fleet, concentrated on the larger fractions of both males and females (Fig. 5). These fractions were generally obtained in areas south of 29[degrees]S (Fig. 1), inshore of the 400 m isobath, and in autumn (April-June) and winter (July-September) months.

Maturation and maturity stages

Males and females in all maturity stages were present in the slope trawling catches off southeastern and southern Brazil (Table 2). The spawning stage (stage VI) was the most frequently identified maturity condition in both sexes and nearly 50% off all individuals caught were at least in an early maturity stage (stage IV and higher). This overall maturity stage composition was observed in 2001-2003 but shifted towards a complete dominance of spawning (and spent) squid after 2003, as the national trawlers that continued to exploit the Argentine shortfin squid tended to catch and land larger males and females (Fig. 6).

Catches included immature males and females as small as 78 and 91 mm ML, respectively. Spawning males (stage VI) and females (stage VII) attained the largest sizes (Table 2). Squids of both sexes enlarged homogenously as maturation progressed. At an advanced maturity-spawning condition (stages V, VI, and VII), however, two distinct size groups were found (Fig. 7). The first group was dominant in the samples and was composed of males and females ranging from 140-180 mm ML and 160-240 mm ML, respectively. The second group was less abundant but included larger individuals (males > 200 mm ML; females > 260 mm ML). Male size-at-maturity was estimated to be 163.3 mm ML and 211.8 mm ML for the smaller and larger modal groups, respectively (Fig. 8). In females, size-at-maturity was estimated to be 201.3 mm ML for the smaller modal group and 292.3 mm ML for the larger one.

[FIGURE 2 OMITTED]

[FIGURE 3 OMITTED]

[FIGURE 4 OMITTED]

[FIGURE 5 OMITTED]

The overall maturity condition of the squid in the catches oscillated in space and time (Fig. 9). The GSI variability in males and females indicated that gonads and accessory organs tended to be relatively larger in the second half of the year in both central and northern latitudinal strata. In the southern areas, however, they enlarged earlier, reaching a maximum in autumn. A similar pattern was also revealed by the Hayashi index, which expresses the advanced maturity condition when values are low (Table 2, Fig. 9).

Sex ratio and mating activity

Overall catches during the 2001-2003 period were slightly but significantly biased towards males (male/female ratio = 1.1; p = 0.001) (Table 3). Season, latitudinal, and depth strata, however, significantly affected this general pattern, particularly as females tended to outnumber males in winter months, both in shallow areas (< 250 m) and along the central latitudinal stratum (Table 3). A contrasting scenario characterized the 2006-2007 samples: females dominated all spatial and temporal situations except in the northern areas (Table 3).

Spermatophore production and storage increased in stage IV males and peaked in fully mature males (stage V) (Table 2). Mating activity was evidenced in the subsequent maturity stages by a sharp decrease in the presence of spermatophores in the Needhan's sac. Similarly, mated females (evidenced by the presence of spermatophores inside the mantle) were generally scarce in the catches obtained between 2001-2003 period (not mated/ mated female ratio = 1.8) (Table 4) except in winter months and > 400 m depths between 25[degrees]-29[degrees]S, where the opposite pattern was observed. On the other hand, mated females largely dominated landings in 2006-2007 (Table 4).

[FIGURE 6 OMITTED]

Stock differentiation

The association among squids caught by trawlers between 2001-2003 was analyzed from the scores produced by the first three PCA extracted factors (axes) that, together, explained 63% and 72% of the total variance in males and females (Table 5). In males, factor 1 was defined mainly by geographical variables (lat, long) and squid size (BW) (higher positive and negative weights, respectively). Consequently, in the graphic representation (Fig. 10), large mature males caught at southwesterly sites should be plotted on the left hemiplane, whereas small mature squid caught at northeasterly sites should appear in the right hemiplane. Depth and maturity condition, as expressed by the Hayashi Index (HI), were particularly important in factor 2 (Table 5); males caught in deep areas with enlarged accessory reproductive organs (i.e. Needham's sac loaded with spermatophores) should be plotted on the left hemiplane and small mature males caught in shallower areas on the right one (Fig. 10). Factor 3 was highly influenced by seasonality, being mostly defined by the day-of-the-year (DYR) (Table 5); squid caught in spring and summer should be plotted in the extremes of the upper and lower hemiplanes, respectively, whereas autumn-winter squids should appear near the center of the axis (Fig. 10). A similar spatial scenario resulted from the three factors obtained with female variables except that factor 2 was also highly influenced by maturity indices (GSI and NGI) and high loads for the depth (DEPTH) variable were placed in factor 3 (Table 5).

In the spatial representation of both males and females, a large group of squid corresponded to small mature animals caught throughout the year in shallower areas of the northeastern slope. In contrast, a smaller group of both sexes, detached from the former group, was composed of large mature animals caught in deep southwestern areas during a restricted period in the middle of the year (winter) (Fig. 10).

[FIGURE 7 OMITTED]

DISCUSSION

Interpreting the biological patterns of I. argentinus from commercial catches off Brazil requires the initial consideration that these patterns may combine the mixed effects of three critical sources: (a) existing biologically distinct population units that may exhibit particular spatial/ temporal distribution patterns, (b) non-random spatial/ temporal fishing strategies that may or may not include squid as a principal target, and (c) on board discards (at least for the national trawl fleet). The two latter sources of bias limit our capacity to comprehensively address the entire population diversity of the species in Brazilian waters. On the other hand, it is possible to conclude, by confronting biological patterns of the catches with synoptic descriptions of the Illex population structure as produced by preceding trawl surveys (Haimovici & Perez, 1990, 1991; Santos & Haimovici, 1997), that different spawning groups can be identified in the commercial catches and, more importantly, that the availability/vulnerability of these groups and their specific biological features may have influenced the trawl fishing patterns on the slope off southern Brazil (Perez & Pezzuto, 2006; Perez et al., 2009b).

[FIGURE 8 OMITTED]

[FIGURE 9 OMITTED]

Samples of commercial catches obtained between 2001-2003 contained immature and maturing squid throughout the year, as well as at least two distinguishable fully mature-spawning groups. The first group, composed of small-sized males and females, was present during all seasons on the shelf-break/ upper slope (< 400 m). In winter-spring, however, a distinctive group of large squid dominated the catches in southern (south of 28[degrees]S) and deep fishing grounds (400-700 m). Both groups had been previously identified in trawl surveys off southern Brazil, the latter being specifically referred to as the southern Brazil stock (SBS) (Haimovici et al., 1998). In the present study, this group was shown to sustain the exceptionally large catches obtained by the chartered trawler "In Sung 270" in September 2001 and also the winter catches produced by national trawlers, mostly from 2003 onwards (Perez & Pezzuto, 2006; Perez et al., 2009b). Unlike the upper slope concentrations of small squid, it seems evident that these large individuals, seasonally available in dense concentrations on the lower slope, attracted the attention of the fishing industry and became valued targets of the developing multispecies deep-water trawl fishery off southern Brazil (Perez & Pezzuto, 2006; Perez et al., 2009b). A relevant issue regarding this pattern, however, has been the fact that SBS squid could actually be connected to the Patagonian shelf stocks through spawning migrations and paralarval transport, as described for other ommastrephid species elsewhere (Hatanaka et al., 1985). If confirmed, this hypothesis would directly characterize a shared stock scenario with important implications for management in Argentina, Uruguay, and Brazil (Haimovici et al., 2007).

Population connections between I. argentinus occurring in the SW Atlantic were formerly addressed by Brunetti (1988), who defined three major stocks occurring off the coast of Argentina and Uruguay (SSS, SPS, and BNS) and concluded that squid distributed along southern Brazil were an extension of the northernmost stock (BNS). Because partly spawned or spent squid were never observed in BNS catches, the spawning location remained uncertain but was speculated to occur between July and September somewhere offshore, north of 38[degrees]S, under the Falkland (Malvinas) or Brazil Currents. Santos & Haimovici (1997) analyzed reproductive patterns of the previously considered SBS members and also concluded that these squid were, in fact, members of BNS, but proposed alternatively that southern Brazil was their major winter-spring spawning ground. Taking into consideration records of elevated concentrations of I. argentinus paralarvae under the core of the Brazil Current (Haimovici et al., 1995) and other evidence derived from trophic relations, parasites, and body proportions (Santos, 1992), Santos & Haimovici (1997) further postulated that maturing BNS squid would migrate in early winter from northern Argentina to southern Brazil slope waters, where spawning would take place under the warm Brazil Current. During spring-summer, as the Subtropical Convergence retracted, egg masses and paralarvae would be transported southwards, allowing recruitment to occur on the southern feeding grounds off northern Argentina (Haimovici et al., 1998). Whereas this hypothesis still requires corroboration through high-resolution methods such as tagging experiments or genetic markers, the biological data from commercial catches off southern Brazil may provide further indirect evidence in its support.

[FIGURE 10 OMITTED]

Initially, the sizes of mature squid present in winter catches off Brazil resembled those reported for members of both BNS and SBS, although precise comparisons were not possible because the different studies included different maturity stages for estimating size-at-maturity. Nonetheless, mantle lengths of males and females of these groups were noticeably larger than those estimated for a presumably "local" upper--slope stock, suggesting that these squid were, in fact, biologically distinct (Table 6). Schwarz & Perez (2007) analyzed the morphology and morphometry of statoliths extracted from squid caught by commercial trawlers off Brazil and reached similar conclusions.

Secondly, the majority of the squid present in the winter catches off Brazil were mated females in a spawning-spent condition, indicating that fishing was concentrated on a spawning event that could be related to a) the spawning seasons proposed for BNS and SBS and b) the spawning grounds proposed for the latter, namely the slope area between 27[degrees]S and 34[degrees]S (Brunetti, 1988; Santos & Haimovici, 1997) (Table 6). Within these grounds, commercial catches further revealed that large spawning squid concentrated in high densities during the day on the deep slope (400-700 m). This pattern was also observed by both fishing and acoustic surveys conducted between 2001 and 2002, which further associated spawning squid concentrations with temperature ranges between 7[degrees] and 13[degrees]C (Madureira et al., 2005; Haimovici et al., 2008). The deep, cold environment off southern Brazil is generally associated with the influence of South Atlantic Central Water (SACW), which flows southwards over the slope as a deep layer of the Brazil Current (Castro et al., 2006). Temperature and salinity within this water mass range from 6-20[degrees]C and 34.6-36.0, respectively, characterizing a considerably colder, less saline environment than that of the overlaying Tropical Water, which is also transported, although superficially, by the Brazil Current. Considering that (a) spawning squid from the Patagonian shelf may require an optimal thermal environment ranging from 4[degrees] to 13[degrees]C (Brunetti et al., 1998) and (b) that pre-reproductive BNS members at the Argentine-Uruguayan Common Fishing Zone (34[degrees]00'-39[degrees]30'S) were shown to concentrate in subantarctic waters between 4-10[degrees]C (Bazzino et al., 2005), it seems reasonable that a spawning migration towards Brazilian waters (Santos & Haimovici, 1997) would take place in association with deep water masses such as SACW. A final element in support of a connection between Brazilian and Patagonian squid stocks can be drawn from the combination of the commercial value of "big squid", the opportunistic behavior of the trawl fishery, and the general evolutionary population strategies of ommastrephid squids (O'Dor, 1992). These squids normally exhibit complex population structures in association with geostrophic currents, protracted spawning, and latitudinal migrations as a strategy to spread--over space and time--the risks of their short, semelparous life cycle (O'Dor, 1998). Because cold, nutrient-enriched temperate waters tend to delay maturity and enhance survivorship of juvenile squid, stocks whose offspring drift, carried by geostrophic currents, to these waters attain larger sizes, are more abundant, and sustain larger fisheries (e.g. I. illecenbrosus, O'Dor & Coelho, 1993; Perez & O'Dor, 1998). Although these squid need to perform long migrations, their large body size favors swimming long distances (O'Dor, 1988). In contrast, those stocks that remain in food-poorer, warmer, tropical and sub tropical waters tend to grow fast but also to mature early at smaller sizes (O'Dor & Coelho, 1993). In a less productive environment, these squids are also less abundant and sustain significantly lower annual landings.

By experiencing their early life in a highly productive and cold environment such as the Patagonian Shelf, BNS squid would tend to be abundant (actually sustaining large catches in the northern Patagonian Shelf) and to mature late in life at large sizes, fit for a ~2,000-km-long winter spawning migration towards Brazilian waters. Because these are cold-water squid, they would tend to reach the deep layers of the slope as they approach southern Brazil, concentrating within the 300-400-m-high SACW layer (Madureira et al., 2005; Castro et al., 2006) and, hence, becoming vulnerable to the slope trawling in winter and early-spring. Off southern Brazil during this period of the year, winter spawners should be markedly distinct from the "local" spawners, both by their larger body size and their deeper bathymetric distribution, attracting the attention first of the highly efficient and exploratory foreign chartered trawlers (Perez et al., 2009b) and later the more conservative but overcapitalized national trawl fleet (Perez & Pezzuto, 2006). In 2002, trawler skippers persistently tried to convince fishing biologists involved with this study that their large catches off Brazil were, in fact, a different squid species due to their obviously different body proportions and suggested that it be given a new name as a marketing strategy (Perez pers. observ.). Albeit anecdotal, this fact highlights the effect of the diversity of this species population (and particular biological attributes) on the observed exploitation patterns in the SW Atlantic, reinforcing the need to consider multinational, shared stock management strategies in the region. Other shellfish and finfish resources exploited in the deep waters off southern Brazil (e.g. deep-water crabs, hake, and others) seem to justify the same strategies (Perez et al., 2009a).

DOI: 10.3856/vol37-issue3-fulltext-11

ACKNOWLEDGEMENTS

The authors are indebted to all observers, captains, and crews that allowed this large body of data to be collected during their commercial operations off southern Brazil. We also thank Rodrigo Sant'Ana for invaluable help with figures. Funding for this study was provided by the Special Secretariat for Aquacul ture and Fisheries (SEAP/PR/027/2007) and the National Council for Scientific and Technological Development (CNPq) research grant (Process 306184/2007-9).

REFERENCES

Bazzino, G., R.A. Quinones & W. Norbis. 2005. Environmental associations of shortfin squid Illex argentinus (Cephalopoda: Ommastrephidae) in the northern Patagonian Shelf. Fish. Res., 76: 401-416.

Boyle, P.R. & P. Rodhouse. 2005. Cephalopods. Ecology and fisheries. Blackwell Publishing, Oxford, 451 pp.

Brunetti, N.E. 1988. Contribucion al conocimiento biologico-pesquero del calamar argentino (Cephalopda, Ommastrephidae, Illex argentinus). Tesis doctoral, Universidad Nacional de La Plata, Buenos Aires, 135 pp.

Brunetti, N.E. 1990. Escala para la identificacion de estadios de madurez sexual del calamar (Illex argentinus). Frente Maritimo, 7: 45-52.

Brunetti, N.E., M.L. Ivanovic & B. Elena. 1998. Calamares omastrefidos (Cephalopoda: Ommastrephidae). In: E. Boschi (ed.). El mar argentino y sus recursos pesqueros, Instituto Nacional de Investigacion y Desarrollo Pesquero, Mar del Plata, 2: 37-68.

Brunetti, N.E., M.L. Ivanovic, E. Louge & H.E. Christiansen. 1991. Reproductive biology and fecundity of two stocks of the squid (Illex argentinus). Frente Maritimo, 8: 73-84.

Castro Fo., J.A. Lorenzzetti, I.C.A. Silveira & L.B. Miranda. 2006. Estrutura termohalina e circulacao na regiao entre o Cabo de Sao Tome (RJ) e o Chui (RS). In: C.L.D.B. Rossi-Wongtschowski & L.S-P. Madureira. (eds.). O ambiente oceanografico da plataforma continental e do talude na regiao sudeste-sul do Brasil, Sao Paulo, EDUSP--Editora da Universidade de Sao Paulo, pp. 11-120.

Costa, P.A.S. & M. Haimovici. 1990. A pesca de lulas e polvos no litoral do Rio de Janeiro. Ciencia & Cultura, 42(12): 1124-1130.

Gasalla, M. de los A., G. Velasco, C.L.D.B. Rossi Wongstchowski, M. Haimovici & L.S-P. Madureira. 2007. Modelo de equilibrio de biomassa do ecossistema marinho da regiao Sudeste-Sul do Brasil entre 100-1000 m de profundidade. Serie Documentos REVIZEE, Score Sul. Instituto Oceanografico, Universidade de Sao Paulo, Sao Paulo, 56 pp.

Haimovici, M. & J.M. Andriguetto Fo. 1986. Cefalopodes costeiros capturados na pesca de arrasto do litoral sul do Brasil. Arq. Biol. Tecnol., 29(3): 473-495.

Haimovici, M. & J.A.A. Perez. 1990. Distribucion y maduracion sexual del calamar argentino, Illex argentinus (Castellanos, 1960) (Cephalopoda: Ommastrephidae), en el sur de Brasil. Sci. Mar., 54: 179-1895.

Haimovici, M. & J.A.A Perez. 1991. Abundancia e distribuicao de cefalopodes em cruzeiros de prospeccao pesqueira demersal na plataforma externa e talude continental do sul do Brasil. Atlantica, Rio Grande, 13(1): 189-200.

Haimovici, M., E.G. Vidal & J.A.A. Perez. 1995. Larvae of Illex argentinus from five surveys on continental shelf of southern Brazil. ICES Mar. Sci. Symp., 199: 414-424.

Haimovici, M., N.E. Brunetti, P.G. Rodhouse, J. Csirke & R.H. Leta. 1998. Chapter 3. Illex argentinus. In: P.G. Rodhouse, E.G. Dawe & R.K. O'Dor (eds.). Squid recruitment dynamics. The genus Illex as a model. The commercial Illex species. Influences on variability. FAO Fish. Tech. Pap., 376: 27-58.

Haimovici, M., J.A.A. Perez & R.A. Santos. 2006. Diagnostico do estoque e orientacoes para o ordenamento da pesca de Illex argentinus (Castellanos, 1960). In: C.L.D.B. Rossi-Wongtshchowski, A.O. Avila-da-Silva & M.C. Cergole (eds.). Analise das principais pescarias comerciais da regiao sudeste-sul do Brasil: dinamica populacional das especies em explotacao. II. Serie Documentos REVIZEE, Score Sul. Instituto Oceanografio, Universidade de Sao Paulo, Sao Paulo, pp. 19-27.

Haimovici. M., A.O. Avila da Silva, L.W. de Miranda & S. Klippel. 2007. Prospeccoes na regiao sudeste-sul. In: M. Haimovici (ed.). A prospeccao pesqueira e abundancia de estoques marinhos no Brasil nas decadas de 1960 a 1990. Levantamento de dados e avaliacao critica. Ministerio do Meio Ambiente. Secretaria de Mudancas Climaticas e Qualidade Ambiental. Programa REVIZEE: Levantamento de Dados Preteritos, Brasilia, pp. 35-74.

Haimovici, M., C.L.D.B. Rossi-Wongstchowski, R.A. Bernardes, L.G. Fisher, C.M. Vooren, R.A. dos Santos, A.R. Rodrigues & S. dos Santos. 2008. Prospeccao pesqueira de especies com rede de arrasto-defundo na regiao sudeste-sul do Brasil. Serie Documentos REVIZEE, Score Sul. Instituto Oceanografico, Universidade de Sao Paulo, Sao Paulo, 183 pp.

Hatanaka, H., S. Kawahara, Y. Uozumi & S. Kasahara. 1985. Comparison of life cycles of five ommastrephid squids fished by Japan: Todarodes pacificus, Illex illecebrosus, Illex argentinus, Nototodarus sloani sloani, and Nototodarus sloani gouldi (Mollusca: Cephalopoda). NAFO Sci. Council Studies, 9: 59-68.

Madureira, L.S-P., R.G.P. Habiaga, A.C. Duvoisin, D. Eliseire Jr., C.F. Soares, S.C. Weigert, C.S. Ferreira & P.A. Saldo. 2005. Identificacao de registros acusticos do calamar argentino Illex argentinus (Castellanos, 1960) no talude da regiao sudeste-sul do Brasil. Serie Documentos REVIZEE, Score Sul. Instituto Oceanografico, Universidade de Sao Paulo, Sao Paulo, 32 pp.

Martins, R.S. & J.A.A. Perez. 2007. The ecology of loliginid squid in shallow waters around Santa Catarina Island, southern Brazil. Bull. Mar. Sci., 80(1): 125-146.

O'Dor, R.K. 1988. Energetic limits on squid distributions. Malacologia, 29(1): 113-119.

O'Dor, R.K. 1992. Big squid in big currents. S. Afr. J. mar. Sci., 12: 225-235.

O'Dor, R.K. 1998. Chapter 11. Squid life-history strategies. In: P.G. Rodhouse, E.G. Dawe & R.K. O'Dor (eds.). Squid recruitment dynamics. The genus Illex as a model. The commercial Illex species. Influences on variability. FAO Fish. Tech. Pap., 376: 233-250.

O'Dor, R.K. & M.L. Coelho. 1993. Big squid, big currents and big fisheries. In: T. Okutani, R.K. O'Dor & T. Kubodera (eds.). Recent advances in cephalopod fisheries biology, Tokay University Press, Tokyo, pp. 385-396.

Perez, J.A.A. 2000. Biomass dynamics of the squid Lo-ligo plei and the development of a small-scale seasonal fishery off southern Brazil. Bull. Mar. Sci., 71(2): 633-651.

Perez, J.A.A. & R.K. O'Dor. 1998. The impact of environmental gradients on the early life inshore migration of the short-finned squid Illex illecebrosus. S. Afr. J. mar. Sci., 20: 294-303.

Perez, J.A.A. & P.R. Pezzuto. 1998. Valuable shellfish species in the by-catch of shrimp fishery in southern Brazil: spatial and temporal patterns. J. Shell. Res., 17: 303-309.

Perez, J.A.A. & P.R. Pezzuto. 2006. A pesca de arrasto de talude do Sudeste e Sul do Brasil: tendencias da frota nacional entre 2001 e 2003. Bolm. Inst. Pesca, Sao Paulo, 32: 127-150.

Perez, J.A.A., R. Wahrlich & P.R. Pezzuto. 2009b. Chartered trawling on the slope off Brazilian coast. Mar. Fish. Rev., 71(2): 24-36.

Perez, J.A.A., P.R. Pezzuto, R. Wahrlich & A.L.S. Soares. 2009a. Deep-water fisheries in Brazil: history, status and perspectives. Lat. Am. J. Aquat. Res., 37(3): 513-541.

Perez, J.A.A., S.H.B. Lucato, H.A. de Andrade, P.R. Pezzuto & M. Rodrigues-Ribeiro. 1998. Programa de amostragem da pesca industrial desenvolvido para o porto de Itajai, SC. Not. Tec. FACIMAR, 2: 93-108.

Perez, J. A.A., R. Wahrlich, P.R. Pezzuto, P.R. Schwingel, F.R.A.Lopes & M. Rodrigues-Ribeiro. 2003. Deep-sea fishery off southern Brazil: recent trends of the Brazilian fishing industry. J. Northw. Atl. Fish. Sci., 31: 1-18.

Santos, R.A. 1992. Relacoes troficas do calamar argentino Illex argentinus (Castellanos, 1960) (Teuthoidea: Ommastrephidae) no sul do Brasil. MSc. Thesis. Fundacao Universidade Federal do Rio Grande, Rio Grande, 83 pp.

Santos, R.A. & M. Haimovici. 1997. Reproductive biology of winter-spring spawners of Illex argentinus (Cephalopoda: Ommastrephidae) off southern Brazil. Sci. Mar., 61(1): 53-64.

Santos, R.A. & M. Haimovici. 2000. The Argentine shortfin squid Illex argentinus (Cephalopoda: Ommastrephidae) in the food webs off southern Brazil. Sarsia, 85: 49-60.

Schwarz, R. & J.A.A. Perez. 2007. Diferenciacao populacional do calamar argentino (Illex argentinus) (Cephalopoda: Teuthida) no sul do Brasil atraves da morfologia e morfometria do estatolito. Braz. J. Aquat. Sci. Technol., 11(1): 1-12.

Received: 23 March 2009; Accepted: 31 August 2009

Jose Angel Alvarez Perez (1), Tiago Nascimento Silva (2), Rafael Schroeder (1,3) Richard Schwarz (1,3) & Rodrigo Silvestre Martins (4,5)

(1) Grupo de Estudos Pesqueiros. Centro de Ciencias Tecnologicas da Terra e do Mar. Universidade do Vale do Itajai, Rua Uruguai 458, Centro, Itajai, SC, Brazil

(2) Biogas Energia Ambiental S.A., Rua Mogeiro 1580. Bairro Perus, 05206-240 Sao Paulo, SP, Brazil

(3) Curso de Pos-Graduacao em Ciencia e Tecnologia Ambiental, Centro de Ciencias Tecnologicas da Terra e do Mar, Universidade do Vale do Itajai, Rua Uruguai 458, Centro, Itajai, SC, Brazil

(4) Marine and Coastal Management (MCM), Private Bag X2, Rogge Bay 8012, Cape Town, South Africa

(5) Zoology Department and Marine Research Centre, University of Cape Town, Private Bag X3, Rondebosch 7701, Cape Town, South Africa

Corresponding author: Jose Angel Alvarez Perez (angel.perez@univali.br)
Table 1. Summary of data for the Argentine shortfin squid Illex
argentinus obtained from chartered and national trawlers
operating off Brazil between 2001 and 2007. N: number of individuals;
Min-Max: smallest and largest mantle length (ML) and total wet body
weight (BW).

Tabla 1. Resumen de datos de calamar argentino Illex argentinus
obtenidos en las operaciones de pesca de arrastreros arrendados y
nacionales en Brasil entre 2001 y 2007. N: numero de individuos,
Min-Max: valores maximos y minimos de la longitud del manto (ML) y
peso total humedo (BW).

                Males                          Females
                         ML (mm)     BW (g)              ML (mm)

Trimester         N      Min-Max    Min - Max     N     Min - Max

Chartered

Jan-Mar/2001                -           -         -         -
Apr-Jun/2001                -           -         -         -
Jul-Sep/2001     32      78 - 195   14 - 240     24     91 - 332
Oct-Dec/2001     966    110 - 278   23 - 425     506    105 - 336
Jan-Mar/2002     395    115 - 221   25 - 295     262    98 - 254
Apr-Jun/2002     466    115 - 239   26 - 345     524    104 - 299
Jul-Sep/2002     153    119 - 316   27 - 570     307    114 - 346
Oct-Dec/2002      4     221 - 275   260 - 420     7     280 - 325
Jan-Mar/2003     73     105 - 191   29 - 188     60     143 - 234
Apr-Jun/2003     131    123 - 200   40 - 192     130    130 - 250
Apr-Jun/2006                -           -                   -
Jul-Sep/2006      7     229 - 259   195 - 325     1        250
Total           2227     78 - 316   14 - 570    1821    91 - 346

National

Jan-Mar/2001      4     154 - 174   76 - 121      6     155 - 185
Apr-Jun/2001     136    129 - 245   30 - 253     213    115 - 395
Jul-Sep/2001     12     190 - 261   163 - 405    16     195 - 315
Oct-Dec/2001     36     135 - 166   38 - 148     89     124 - 204
Jan-Mar/2002     81     114 - 254   30 - 309     125    117 - 262
Apr-Jun/2002     86     100 - 250   30 - 335     88     130 - 376
Jul-Sep/2002     95     110 - 340   31 - 450     86     118 - 350
Oct-Dec/2002      5     220 - 262   211 - 249     8     252 - 367
Jan-Mar/2003                -           -                   -
Apr-Jun/2003     27     159 - 225   100 - 315    16     190 - 290
Apr-Jun/2006     24     130 - 210   49 - 162     51     117 - 305
Jul-Sep/2006     43     110 - 289   128 - 470    45     166 - 351
Oct-Dec/2006     73     111 - 249   28 - 390     77     132 - 344
Jan-Mar/2007
Apr-Jun/2007     75     145 -246     50 - 299    122    135 - 338
Jul-Sep/2007     46     160 - 289   116 - 505    54     223 - 353
Oct-Dec/2007
Total            743    100 - 340   28 - 505     996    115 - 395
TOTAL           2970     78 - 340   14 - 570    2817    91 - 395

                 Females

                 BW (g)

Trimester       Min - Max

Chartered

Jan-Mar/2001        -
Apr-Jun/2001        -
Jul-Sep/2001    18 - 455
Oct-Dec/2001    33 - 655
Jan-Mar/2002    18 - 320
Apr-Jun/2002    23 - 560
Jul-Sep/2002    26 - 775
Oct-Dec/2002    228 - 670
Jan-Mar/2003    52 - 260
Apr-Jun/2003    43 - 400
Apr-Jun/2006        -
Jul-Sep/2006       162
Total           18 - 775

National

Jan-Mar/2001    79 - 145
Apr-Jun/2001    32 - 580
Jul-Sep/2001    90 - 655
Oct-Dec/2001    39 - 255
Jan-Mar/2002    31 - 375
Apr-Jun/2002    44 - 605
Jul-Sep/2002    25 - 830
Oct-Dec/2002    196 - 580
Jan-Mar/2003        -
Apr-Jun/2003    180 - 645
Apr-Jun/2006    68 - 700
Jul-Sep/2006    57 - 860
Oct-Dec/2006    35 - 870
Jan-Mar/2007
Apr-Jun/2007    37 - 740
Jul-Sep/2007    184 - 910
Oct-Dec/2007
Total           25 - 910
TOTAL           18 - 910

Table 2. Summary of the maturity conditions of the Argentine shortfin
squid Illex argentinus in commercial trawl catches off Brazil between
2001 and 2007. Examined males and females were pooled by maturity
stages (after Brunetti, 1990) and the relative and cumulative
frequencies of each stage were calculated and expressed in
percentages (% and Cum.% respectively). The largest (Max) and
smallest (Min) mantle length of squid in each maturity stage are
indicated. Males with no, few, and many spermatophores (spermat.)
in the Needhan's sac and females with and without spermatophores at
the base of the gills were also quantified for each maturity stage.

Tabla 2. Resumen de las condiciones de madurez sexual de calamar
argentino Illex argentinus en capturas comerciales de la pesca de
arrastre en Brasil entre 2001 y 2007. Los machos y hembras examinados
fueron agrupados por estadios de madurez (segun Brunetti, 1990). Para
cada estadio se calcularon las frecuencias relativas y acumuladas
expresadas en valores porcentuales (% y Cum.% respectivamente). Para
cada estadio de madurez sexual se indica la longitud maxima (Max) y
minima (Min) del manto. Tambien se contaron para cada estadio de
madurez los machos con ninguno, pocos o muchos espermatoforos
(spermat.) en la bolsa de Needhan y las hembras con y sin
espermatoforos en las bases de las branquias.

                                       Maturity stages

                              Immature+Maturing          Mature

                             I       II      III       IV       V

Males               N       108     286      517      621      535
                    %       3.6     9.6      17.4     20.9     18.0
                  Cum.%     3.6     13.3     30.7     51.6     69.6
  ML               Max      199     218      254      260      316
                   Min      78      100      102      111      122
  GSI              Mean    1.02     1.93     3.56     4.86     5.58
                   (SE)    (0.11)  (0.10)   (0.10)   (0.12)   (0.07)
  HI               Mean    0.60     0.65     0.72     0.64     0.46
                   (SE)    (0.02)  (0.01)   (0.01)   (0.01)   (0.01)
  No spermat.       N       109     286      517       0        2
                    %      11.9     31.2     56.4     0.0      0.2
                  Cum. %   11.9     43.1     99.6     99.6     99.8
  Few spermat.      N        0       0        0       625       3
                    %       0.0     0.0      0.0      38.9     0.2
                  Cum. %    0.0     0.0      0.0      38.9     39.1
  Many spermat.     N        0       0        0        0       540
                    %       0.0     0.0      0.0      0.0     100.0
                  Cum. %    0.0     0.0      0.0      0.0     100.0
Females             N       183     365      344      366      383
                    %       6.5     13.0     12.2     13.0     13.6
                  Cum. %    6.5     19.5     31.7     44.7     58.3
  ML               Max      205     213      277      299      334
                   Min      91      115      124      104      105
  GSI              Mean     2.4     2.6      3.7      13.6     25.2
                   (CE)    (0.7)   (0.3)    (0.2)    (0.4)    (0.8)
  HI               Mean    0.51     0.48     0.48     0.46     0.38
                   (CE)    (0.01)  (0.01)   (0.01)   (0.01)   (0.01)
  Mated             N       183     368      347      370      383
                    %      11.1     22.3     21.0     22.4     23.2
                  Cum. %   11.1     33.4     54.4     76.8     99.9
  Non-mated         N        0       0        1        1        2
                    %       0.0     0.0      0.1      0.1      0.1
                  Cum. %    0.0     0.0      0.1      0.1      0.3

                                Maturity stages

                                 Spawning+Spent

                             VI       VII      VIII    Total

Males               N        728      174       -      2969
                    %       24.5      5.9       -
                  Cum.%     94.1     100.0      -
  ML               Max       340      302               340
                   Min       110      131               78
  GSI              Mean     5.09      4.27
                   (SE)    (0.08)    (0.31)
  HI               Mean     0.51      0.43
                   (SE)    (0.01)    (0.02)
  No spermat.       N         1        1        -       916
                    %        0.1      0.1       -
                  Cum. %    99.9     100.0      -
  Few spermat.      N        791      189       -      1608
                    %       49.2      11.8      -
                  Cum. %    88.2     100.0      -
  Many spermat.     N         0        0        -       540
                    %        0.0      0.0       -
                  Cum. %    100.0    100.0      -
Females             N        643      399      134     2817
                    %       22.8      14.2     4.8
                  Cum. %    81.1      95.2    100.0
  ML               Max       351      395      367      395
                   Min       242      262      120      91
  GSI              Mean     25.1      19.5     16.0
                   (CE)     (0.4)    (0.5)    (0.9)
  HI               Mean     0.30      0.27     0.20
                   (CE)    (0.00)    (0.01)   (0.02)
  Mated             N         0        0        1      1652
                    %        0.0      0.0      0.1
                  Cum. %    99.9      99.9    100.0
  Non-mated         N        665      529      157     1354
                    %       49.1      39.1     11.6
                  Cum. %    49.4      88.5    100.1

Table 3. Sex ratio of the Argentine shortfin squid Illex argentinus
in commercial trawl catches off Brazil in two periods: 2001-2003
and 2006-2007. M/F: male/female ratio, p: probability
([[PI].sup.2]). Values in bold correspond to probabilities obtained
by contingency table analysis to compare the effects of trimesters,
depth, and latitudinal strata on the sex-ratio.

Table 3. Proporcion de sexos del calamar argentino Illex argentinus
en capturas de la pesca comercial de arrastre en Brasil en dos
periodos: 2001-2003 y 2006-2007. M/F: fraccion numero de machos/
numero de hembras; p: probabilidad ([[PI].sup.2]). Valores en negrita
corresponden a probabilidades resultantes del analisis de la tabla
de contingencia para comparar los efectos de trimestres, estratos
batimetricos y estratos latitudinales sobre la proporcion sexual.

                           2001-2003                 2006-2007

Trimester       Males   Females    M/F      p      Males   Females

Jan-Mar          553      453      1.2    0.002      0        0
Apr-Jun          846      971      0.9    0.003     164      308
Jul-Sep          292      433      0.7   < 0.001    126      155
Oct-Dec         1011      610      1.7   < 0.001    73        77
p                                        < 0.001

Depth strata

< 250 m          224      313      0.7   < 0.001    46        60
250 - 400       1992      1822     1.1    0.006     145      214
> 400 m          450      288      1.6   < 0.001    172      266
p                                        < 0.001

Latitudinal strata

North           2015      1537     1.3   < 0.001    77        57
Centre           483      741      0.7   < 0.001    25       101
South            144       78      1.8   < 0.001    226      338
p                                        < 0.001
Total           2702      2467     1.1    0.001     363      540

                 2006-2007

Trimester       M/F      p

Jan-Mar          -       -
Apr-Jun         0.5   < 0.001
Jul-Sep         0.8    0.084
Oct-Dec         0.9    0.74
p                      0.002

Depth strata

< 250 m         0.8
250 - 400       0.7
> 400 m         0.6
p                      0.736

Latitudinal strata

North           1.4    0.137
Centre          0.2   < 0.001
South           0.7   < 0.001
p                     < 0.001
Total           0.7    0.002

Table 4. Evidence of mating in female Argentine shortfin squid Illex
argentinus caught in commercial trawl catches off Brazil in two
periods: 2001-2003 and 2006-2007. N/M: not mated/mated female
fraction, p-values correspond to probabilities obtained by
contingency table [[PI].sup.2] analysis to compare the effects of
trimesters, depth, and latitudinal strata on the mated condition of
females.

Tabla 4. Evidencias de copula en hembras de calamar argentino Illex
argentinus capturado por la pesca comercial de arrastre en Brasil en
dos periodos: 2001-2003 y 2006-2007. N/M: fraccion
no-copuladas/copuladas. P: probabilidades resultantes del analisis
[[PI].sup.2] para comparar los efectos de trimestres, estratos
batimetricos y estratos latitudinales sobre la actividad de copula
de las hembras.

                       2001-2003                    2006-2007

            Not-mated    Mated     N/M   Not-mated    Mated    N/M

Trimester
Jan-Mar        339        114      3.0
Apr-Jun        752        219      3.4      20         288     0.1
Jul-Sep        67         366      0.2      26         128     0.2
Oct-Dec        423        187      2.3      25         52      0.5
p                        <0.001                      <0.001

Depth Strata

< 250 m        150        163      0.9       6         54      0.1
250 - 400     1281        541      2.4      39         175     0.2
> 400 m        107        181      0.6      26         239     0.1
p                        <0.001                       0.019

Latitudinal strata

North         1201        336      3.6      23         34      0.7
Centre         262        479      0.5       9         92      0.1
South          47          31      1.5      38         299     0.1
p                        <0.001                      <0.001
Total         1581        886      1.8      71         468     0.2
p                        <0.001                      <0.001

Table 5. Principal Component Analysis employed to differentiate
Argentine shortfin squid Illex argentinus stocks within the catches
obtained by commercial trawlers off Brazil between 2001 and 2003.
Variables included were: day-of-the-year (DYR), decimal latitude
(LAT), decimal longitude (LONG), depth (DEPTH), body wet weight
(BW), gonadosomatic index (GSI), Hayashi index (HI), Nidamental
gland/Testis Index. The linear coefficients of the variables
(loadings) in the first three factors rotated by the PCA are
indicated for males and females. The eigenvalues and the variance
explained by each factor are indicated in the last three rows.

Tabla 5. Analisis de Componentes Principales aplicada en la
diferenciacion de los stocks de calamar argentino Illex argentinus
en las capturas de arrastreros comerciales en Brasil entre 2001 y
2003. Las variables incluidas fueron: dia-delano (DYR), latitud
decimal (LAT), longitud decimal (LONG), profundidad (DEPTH), peso
humedo del cuerpo (BW), indice gonadosomatico (GSI), indice de
Hayashi (HI), indice de la glandula nidamental/ testiculo. Los
coeficientes lineales de las variables (pesos) en los tres primeros
factores rotacionados por el PCA se indican para machos y hembras.
Los valores propios y la varianza explicada por cada factor se
indican en las ultimas tres lineas.

Component                Males                     Females
                         Factor                     Factor

                 1        2        3        1        2        3

DYR             -0.105   -0.051    0.846   -0.379    0.043    0.662
LAT              0.929    0.157    0.090    0.952    0.031    0.084
LONG             0.896    0.306    0.102    0.940    0.117   -0.008
DEPTH           -0.006    0.694   -0.163    0.105    0.445   -0.686
BW              -0.699    0.358   -0.020   -0.737    0.059   -0.282
GSI              0.149    0.310    0.453    0.027    0.873    0.114
HI               0.425   -0.683   -0.213    0.363   -0.685    0.014
NGI / TI         0.185    0.392   -0.427    0.128    0.766    0.263
Eigenvalue       2.403    1.447    1.195    2.639    2.037    1.079
Variance        30.035   18.087   14.933   32.983   25.461   13.483
  explained
  (%)
Cum. variance   30.035   48.122   63.055   32.983   58.444   71.927
  explained
  (%)

Table 6. Summary of characteristics of two stocks of the Argentine
shortfin squid Illex argentinus in waters of the northern Patagonian
shelf (BNS) and southern Brazil (SBS) in comparison with spawning
groups differentiated in the commercial trawl catches off southern
Brazil between 2001 and 2007. Sizes at maturity refer to modal mantle
lengths of males and females in different maturity stages (between
parentheses) as defined by Brunetti (1990).

Tabla 6. Resumen de las caracteristicas de dos stocks de calamar
argentino Illex argentinus en el norte de la plataforma patagonica
(BNS) y el sur de Brasil (SBS) en comparacion con los grupos
desovantes diferenciados en las capturas comerciales de pesca de
arrastre en el sur de Brasil entre 2001 y 2007. La talla de madurez
sexual corresponde a la longitud modal del manto de machos y hembras
en diferentes estadios de madurez (entre parentesis) definidos por
Brunetti (1990).

                                 Proposed stocks

                    Bonaerensis-north          Southern
                   patagonic (BNS) (1)     Brazil (SBS) (2)

Spawning Grounds    Slope, north of         Slope, between
                      38[degrees]S,          27[degrees]S
                   under the Falkland/   and 34[grados]S under
                   Malvinas Current or    the Brazil Current
                     Brazil Current

Spawning season     July - September        July - November
Modal size at        Males: ~200 mm         Males: ~250 mm
maturity (ML)       Females: ~240 mm       Females: ~300 mm
                      (Stages IV+V)          (Stages > V)

                         Commercial catches off Brazil

                          Large                 Small
                       spawners (3)          spawners (3)

Spawning Grounds   Between 26[degrees]        North of
                    and 29[degrees]S,       28[degrees]S,
                     360-520 m depth      shallower than 360
                                               m depth

Spawning season      July - September       All year-round
Modal size at         Males: 212 mm         Males: 161 mm
maturity (ML)        Females: 292 mm       Females: 201 mm
                      (Stages > IV)         (Stages > IV)

(1) Brunetti et al. (1991), (2) Santos & Haimovici (1997),
(3) This study.
COPYRIGHT 2009 Pontificia Universidad Catolica de Valparaiso, Escuela de Ciencias del Mar
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2009 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Title Annotation:Research Article
Author:Perez, Jose Angel Alvarez; Silva, Tiago Nascimento; Schwarz, Richard; Schroeder, Rafael; Martins, Ro
Publication:Latin American Journal of Aquatic Research
Article Type:Report
Date:Nov 1, 2009
Words:8222
Previous Article:Biomass and fishing potential yield of demersal resources from the outer shelf and upper slope of southern Brazil/Biomasa y rendimiento potencial...
Next Article:Sexual maturity of the deep-sea red crab Chaceon notialis Manning & Holthuis, 1989 (Brachyura: Geryonidae) in southern Brazil/Madurez sexual del...
Topics:

Terms of use | Privacy policy | Copyright © 2020 Farlex, Inc. | Feedback | For webmasters