Printer Friendly

Biological parameters of the burrowing crayfish, Parastacus pugnax (Poeppig, 1835), in Tiuquilemu, Bio-Bio Region, Chile/Parametros biologicos del camaron excavador, Parastacus pugnax (Poeppig, 1835) en Tiuquilemu, Region del Bio-Bio, Chile.

INTRODUCTION

Six of the species of malacostracas inhabiting Chilean freshwaters belong to the family Parastacidae (Rudolph & Crandall, 2005, 2007; Jara et al, 2006): Parastacus pugnax (Poeppig, 1835), P. nicoleti (Philippi, 1882), Samastacus spinifrons (Philippi, 1882), Virilastacus araucanius (Faxon, 1914), V. rucapihuelensis (Rudolph & Crandall, 2005), and V. retamali (Rudolph & Crandall, 2007). Of these, P. pugnax and S. spinifrons are intensely exploited for human consumption (Porter, 1904; Rudolph, 2002). Although the situation of P. pugnax is "vulnerable" throughout most of its distribution area (Bahamonde et al., 1998), few works have studied the biological aspects of this species; such studies are necessary to regulate its exploitation. Most research on P. pugnax concentrates on the study of the first postembryonic stages (Rudolph & Rios, 1987), intersex (Rudolph, 1997; Martinez & Rudolph, 2011), proximate composition of the meat (Rudolph et al., 1991), and ecological aspects of the species (Arias & Munoz, 1991; del Valle, 2002).

The burrowing crayfish (P. pugnax) is endemic to central-southern Chile (Jara et al., 2006), where it is distributed from Rio Aconcagua (32[degrees]50'S, 70[degrees]59'W) to Carahue (38[degrees]40'S, 73[degrees]09'W) (Rudolph, 1997). This crayfish builds underground galleries reaching up to 2 m depth in low-lying, semi-boggy ground known locally as vegas or gualves (Kilian, 1959; Bahamonde & Lopez, 1963). These galleries may have from one to 14 entrances (del Valle, 2002). In winter, the artisanal exploitation of this crustacean provides an alternative income for local farmers (Arias & Munoz, 1991; Rudolph et al., 1991). At present, no official records track the exploited volume of P. pugnax. However, Silva & Spoerer (2006) report that each year some 43.5 million specimens are extracted and, if we consider that the average weight of the specimens sold is 30 g, then the approximate level of annual catches would be 1,260 ton, nearly one-third the volume of the nylon shrimp (Heterocarpus reedi) catches recorded in the same period (SERNAPESCA, 2005); H. reedi is one of the most important marine crustacean resources in terms of extraction volume in Chile.

The present work was developed given the scant information available on the population parameters for this crayfish. In order to determine the variations produced during an annual cycle, we isolated a section of low-lying ground in central-southern Chile inhabited by P. pugnax, as this allowed us to monitor a population undisturbed by human intervention. The research was aimed mainly at determining the growth, size structure, and reproductive aspects of P. pugnax. This information is necessary for the extractive management of the species and for determining its possibilities for culturing.

MATERIALS AND METHODS

The study was done in Tiuquilemu (36[degrees]22'S, 71[degrees]38'W), in the far north of the Bio Bio Region, Chile, where locals extract crayfish from the low-lying lands. The study area consisted of 900 [m.sup.2] enclosed with a fence made up of smooth and barbed wire and a nylon mesh sunk into the ground. This prevented the escape or entrance of crayfish during the study period.

Systematic monthly samples were taken from the fenced area between August 2007 and August 2008. During this period, 3,512 individuals were caught, pulling them from their tunnels with an artisanal vacuum pump. Females carrying eggs and adult specimens accompanied by offspring were examined in the field and returned immediately to their tunnels so as to keep the juveniles from their habitat for as short a time as possible, minimizing the impact on the studied population. For each specimen, we recorded the carapace length (CL) measured from the eye orbit to the furca of the carapace (Arias & Munoz, 1991), total weight (TW), sex, and the total number of eggs carried by the females were recorded. Individuals fewer than 26 mm CL were categorized as undetermined, since it was not possible to distinguish the sex of these specimens with the naked eye (Rudolph, 1997).

Monthly size structures were constructed, grouping the measurements of CL in intervals of 1 mm. The size structures were done separately for males, total females, ovigerous females, undetermined, and total specimens (males, total females, and undetermined). In each case, the average length and standard deviation were estimated.

The length-weight ratio was determined separately for P. pugnax males and females, using the power function: [TW.sub.i] = a [CL.sub.i.sup.b], where [TW.sub.i] and [CL.sub.i] are the total weight and cephalothoracic length of the i-th individual, and a and b are the parameters of the potential function. Student's t-test ([t.sub.[alpha]/2, n-2]) was used to establish the type of relative growth (allometric-isometric) presented by this species (Dixon & Massey, 1957). Moreover, an [F-test.sub.(1-[alpha]; 2; n1+n2-4)] was used to compare the curves of the length-weight ratio for the two sexes (Neter & Wasserman, 1974).

The global sexual proportion and sexual proportion with respect to length were calculated monthly. In the latter case, a null hypothesis ([H.sub.0]) that the proportion of the sample is equals to the theoretical proportion expected of 50% of the males and an equal proportion of females was cpnsidered. The test statistic was defined by:

[Z.sub.c] = [[??] - [P.sub.0]]/[square root of P(1 - [P.sub.0]/n]

Thus, the null hypothesis was rejected if [Z.sub.c] > [Z.sub.t] with [alpha] = 5% and one degree of freedom.

The egg-carrying period was determined according to the monthly percentage of ovigerous females over the total females in the sample. To define the period of maximum incidence of ovigerous females (females carrying eggs + females with embryos + juveniles 1 and 2), we considered the periods in which we found percentages equal to or greater than 25% of females incubating eggs (Arana et al., 1976). Later, we established the relationship existing between the number of eggs and the cephalothoracic length of the carrying females (Arana & Tiffou, 1970; Arana et al., 1985; Sanchez et al., 2008) was established. In order to determine the expression that best represents the ratio between CL and fecundity, five mathematical models used previously by Palma & Arana (1997), were tested.

To determine the size at first maturity ([SFM.sub.50%]), we calculated the proportion of ovigerous females (OF) with respect to the total number of females in each range of CL of 1 mm was calculated. These data were fit to a sigmoid curve given by the expression:

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]

where %OF corresponds to the percentage of ovigerous females at each length, and a and b are the parameters of the adjusted model.

The Von Bertalanffy growth curve and its parameters ([CL.sub.[infinity]], K, [t.sub.0]) were determined using modal progression analysis. The modal groups were identified using the Bhattacharya method (1967). Once the parameter [CL.sub.[infinity]] was determined, the estimate of [t.sub.0] was done through the graph and the equation proposed by Von Bertalanffy (1934), whose expression corresponds to:

-ln(1 - CL(t)/CL[infinity]) = -K x [t.sub.0] + K x t

RESULTS

Undetermined specimens of P. pugnax ranged in size from 5.5 to 26 mm CL. It was possible to sex individuals between 25.5 and 53.7 mm (males) and 26.7 and 52.8 mm (females). The average carapace length varied monthly between 38.8 and 42.2 mm (males) and between 36.2 and 44.4 mm (females) (Table 1).

The size-frequency distributions showed polymodal structures in most months. Bi-modal structures were observed for both males and females in December 2007. In the period analyzed, specimens between 20 and 30 mm CL were scarce, and between August and October 2007 and February and June 2008, no specimens were recorded between 20 and 25 mm CL (Fig. 1).

The potential fit of the length-weight relationship revealed values of 0.00053 and 2.97 in males and 0.00050 and 2.99 in females, corresponding to the parameters a and b, respectively (P < 0.05) (Figs. 2a-2b). No significant differences were found between sexes in this ratio ([F.sub.c] = 0.29 < [F.sub.t(0 05; 2; 1391)] = 3.002). Thus, the common equation was defined by the parameters a = 0.00052 and b = 2.98 (P < 0.05) (Fig. 2c). The isometric test determined isometric growth in P. pugnax ([t.sub.c] = 1.54 < [t.sub.t] = 1.96).

In general, the global monthly sexual proportion showed a slight predominance of males; the proportion of females was only greater in November 2007. Nonetheless, no significant differences were found in most samples with respect to the expected relationship of 1:1 (P < 0.05); the only exceptions occurred in March and May 2008. As for the sexual proportion with respect to the length, males were relatively predominant in all months for most of the sizes considered in the samples (Fig. 3).

The presence of ovigerous females was recorded for five consecutive months, with the exception of January, when no sampling was carried out. Thus, the greater number of ovigerous females in summer was noteworthy. On the contrary, no ovigerous females were recorded from August to October 2007 or from April to August 2008. The maximum period of egg-carrying occurred between December and April 2008, and the percentage of ovigerous females was highest in February of this same year (Fig. 4).

The fecundity of P. pugnax was estimated by analyzing 145 ovigerous females whose length ranged from 27.9 to 52.4 mm CL. Of these, individual fecundity varied between five and 46 eggs. According to the different mathematical models used to define the relationship between cephalothoracic length and the total number of eggs (TNE) carried by the females, it was determined that the data best fit to the linear model TNE = -26.76 + 1.31 CL (R2 = 0.8, P < 0.05) (Fig. 5).

The presence of mature females was determined as of 28 mm CL, and as of 47 mm CL, 100% of the females were found in this condition. Therefore, it was not necessary to re-scale the data in order to fit them to the maturity ogive. Thus, the length was determined at first maturity to be 38.1 mm CL (Fig. 6).

The parameters of the Von Bertalanffy growth curve, estimated using modal progression analysis (Fig. 7), were [CL.sub.[infinity]] = 55.3 mm, K = 0.23 mm [year.sup.1], and [t.sub.0] = -0.58 (Fig. 8).

DISCUSSION

In this study, P. pugnax ranged in length from 5.5 to 53.7 mm CL. This was similar to the lengths reported by del Valle (2002) of 4.7 to 52 mm CL, but different from those found by Arias & Munoz (1991) and Rudolph (1997) of 8 to 49 mm and 6.6 to 47.4 mm CL, respectively.

In general, the average carapace length of P. pugnax females was greater than that of the males; the average CL was greater for males in only three of the 12 samplings (Table 1). This could be associated with the fact that the females are prepared physically to carry eggs and care for offspring, as shown by Rudolph (1997), who determined that females have abdomens that are, on average, wider and longer than the males.

The size structure revealed, in most months, at least three modal groups. In March 2008, it was observed the appearance of a new group, due possibly to a prior cohort. The size structures of adult specimens were identified as of December 2007, which could possibly be associated with the larger sample size taken on this date. The low proportion of specimens between 20 and 30 mm CL determined in most of the samplings is similar to that found by Arias & Munoz (1991), who recorded a similar decrease in the percentage frequencies, especially in the size range between 16 and 25 mm CL. Rudolph (1997) did not register the presence of specimens between 20 and 25 mm CL in November 1994, or June and October 1995, but did detect specimens--albeit a low quantity--in this length range in most of the remaining months. Likewise, the P. pugnax size structures presented by del Valle (2002) reveal a low amount of specimens between 21 and 31 mm CL.

This particular length structure observed in P. pugnax, still has no clear explanation. Nonetheless, a first hypothesis is that the specimens reach between 12 and 18 mm CL in winter and begin to dig small holes off the parental tunnels or galleries (Del Valle, 2002). This would hinder their extraction and at the same time reduce their probability of being caught until reaching a larger size.

The estimated length-weight ratio indicated no statistically significant differences between the ratios established for the two sexes, further determining that the growth of this species is isometric in type (b[approximately equal to]]3). This result differs from that obtained for Samastacus spinifrons, which showed isometric growth in the males and negative allometric growth in the females (Bocic et al, 1988). Thus, there is no common pattern in the length-weight ratio for species of a single family or sexes of a single species.

The global sexual proportion, in general, was slightly predominated by males in most months of this study. Nonetheless, the proportion of males and females did not differ from the expected ratio of 1:1, which agreed with the results obtained by Rudolph (1997) for specimens over 25 mm CL. Likewise, Rudolph (2002) studied the global sexual proportion in S. spinifrons, determining that, in general, males were predominant. However, these proportions were as expected (1:1) for the sexes. The same was true of Parastacus defossus (Noro & Buckup, 2009), P. brasiliensis (Fontoura & Buckup, 1989a, 1989b), and other Parastacidae species (Noro & Buckup, 2009).

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

The sexual proportions with respect to the length, in general, showed predominance of males in most length ranges. This coincided with that determined by Rudolph (1997) for some class-size intervals; that author found that males were predominant in length ranges < 26 mm CL and between 40 and 49.9 mm CL.

The results showed the presence of ovigerous females between November 2007 and May 2008, with a maximum proportion of specimens in this condition in February 2007. In another study, Del Valle (2002) caught one ovigerous female in December 1999 and two females in the post-embryonic incubation phase in January 2000. Moreover, Rudolph (1997) recorded the presence of ovigerous females in October, November, and January, similar to the period established in the present study. Thus, it is possible to deduce that the period of egg-carrying for P. pugnax lasts from mid-spring to the end of autumn. Our study differs from those of the aforementioned authors in terms of the proportion of females with eggs: whereas it was found a maximum of 67.2% of the females were ovigerous (February 2008), Del Valle (2002) recorded one ovigerous female and only 10% of the females in the study by Rudolph (1997) were carrying eggs.

The size at first maturity of P. pugnax was estimated to be 38.1 mm CL, similar to that presented by Rudolph (1997), who did not record the presence of ovigerous females under 30 mm CL. The same author indicated that the maturity of the females begat at approximately 26 mm CL, the size at which the pubertal molt occurs, agreeing with that registered in the present investigation, in which ovigerous females under 28 mm CL were not recorded.

The fecundity determined herein was lower than the maximum found previously for this species. Low fecundity is characteristic of crayfish with semi-terrestrial lives, as compared with others such as S. spinifrons; this fact is related to the direct development that characterizes these freshwater crustaceans (Rudolph, 2002) and the extensive care of their offspring (Del Valle, 2002). Histological analyses have shown this species to have a maximum of 100 oocytes (E. Rudolph, pers. comm.), allowing us to suppose that it is possible to increase their fecundity under special culturing conditions.

In this study, females with a minimum of three and a maximum of 43 eggs were found. These results coincide with those presented by other authors on P. pugnax, whose range of fecundity varied between 6 and 71 eggs (Dalannais, 1984; Rudolph & Rios, 1987; Rudolph, 1997; Del Valle, 2002). As in studies of other freshwater shrimp species, this relationship was best represented by a linear function (Sanz, 1986; Rudolph, 2002; Alvarez & Rangel, 2007).

In terms of the parameters of the estimated growth curve, the value of [CL.sub.[infinity]] was similar to the maximum values of CL found in the studies of this species done by Arias & Munoz (1991), Rudolph (1997), and Del Valle (2002). The differences between the growth curves found in this study and those estimated by Del Valle (2002) may have been influenced by the different sampling designs applied in the two studies: in the former, individuals were collected from different arbitrarily selected zones in low-lying lands whereas in the latter, a systematic sampling design was applied over a single population.

[FIGURE 3 OMITTED]

[FIGURE 4 OMITTED]

[FIGURE 5 OMITTED]

[FIGURE 6 OMITTED]

[FIGURE 7 OMITTED]

[FIGURE 8 OMITTED]

Moreover, it was not possible to differentiate the size structure of the adult specimens presented by Del Valle (2002), which could affect the modal progression analysis, which is based on the differences of the average sizes or modal lengths of the cohorts born in different years or seasons (Sparre & Venema, 1997). It should be noted that the low-lying lands sampled in the Del Valle (2002) study were used for agricultural activities, modifying the environment of the resource. This factor could have determined the differences found between the growths curves of these two studies.

The value of [CL.sub.[infinity]] estimated in this study (55.3 mm) was similar to that determined by Ibarra & Arana (2011) (55.9 mm) through the technique of marking and re-capturing. Nonetheless, certain differences were noticed between the growth rates (K) estimated in both studies, which caused discrepancies in the time required by these species to reach the salable size of 30 mm CL that has been established for S. spinifrons (Rudolph et al., 2010). According to Ibarra & Arana (2011), this would be reached in 3.1 years and according to the present study, in 1.9 years. This discrepancy could be attributed to a possible negative effect in growth when using tags adhered to the body of the organisms or rather to an overestimate of the age when using the modal progression method, as noted by different authors (e.g. Morales-Nin, 1989; Keyl et al, 2011).

According to our results, the growth, maximum length, and reproduction of P. pugnax are similar to those of S. spinifrons, a Parastacidae known to have a high potential for farming (Rudolph et al., 2010). S. spinifrons can reach a maximum length of 62.2 mm CL (Rudolph, 2002) and has fecundity of up to 192 eggs per female, post-embryonic development, and extensive parental care (Rudolph et al., 2010), among other characteristics. Thus, P. pugnax could also be considered to be in this category, and the data generated and gathered in this study could be used to create proposals intending to diversify Chilean aquaculture to include astaciculture and, specifically, P. pugnax.

DOI: 10.3856/vol40-issue2-fulltext-16

ACKNOWLEDGEMENTS

The authors appreciate the valuable suggestions made by anonymous reviewers.

REFERENCES

Alvarez, F. & R. Rangel. 2007. Estudio poblacional del acocil Cambarellus montezumae (Crustacea: Decapoda: Cambaridae) en Xochimilco, Mexico. Rev. Mex. Biodivers., 78: 431-437.

Arana, P. & M. Tiffou. 1970. Madurez sexual, sexualidad y fecundidad del camaron nylon (Heterocarpus reedi). Invest. Mar., Valparaiso, 1(11): 260-281.

Arana, P., E. Dupre & V. Gaete. 1985. Ciclo reproductivo, talla de primera madurez sexual y fecundidad de la langosta de Juan Fernandez (Jasus frontalis). In: P. Arana (ed.). Investigaciones marinas en el archipielago de Juan Fernandez. Universidad Catolica de Valparaiso, Valparaiso, pp. 187-211.

Arana, P., L. Noziglia & G. Yany. 1976. Crecimiento, reproduccion, factor de condicion y estructura poblacional del camaron nylon (Heterocarpus reedi) (Crustacea, Decapoda, Caridea). Cien. Tecnol. Mar, 2: 3-98.

Arias, P. & D. Munoz. 1991. Antecedentes bioecologicos del camaron de vega Parastacus pugnax (Poeppig, 1835), en el area de Chillan. Agro-Ciencia, 7(2): 167-172.

Bahamonde, N., A. Carvacho, C. Jara, M.T. Lopez, F. Ponce, M.A. Retamal & E. Rudolph. 1998. Categorias de conservacion de Decapodos nativos de aguas continentales de Chile. Bol. Mus. Nac. Hist. Nat., 47: 91-100.

Bahamonde, N. & M.T. Lopez. 1963. Decapodos de aguas continentales en Chile. Invest. Zool. Chil., 10: 123-149.

Bhattacharya, C.G. 1967. A simple method of resolution of a distribution into Gaussian components. Biometrics, 23: 115-135.

Bocic, V., E. Rudolph & D. Lopez. 1988. Biologia reproductiva y dinamica poblacional del camaron de rio Samastacus spinifrons (Philippi, 1882). Bol. Soc. Biol. Concepcion, Concepcion, Chile, 59: 9-21.

Dalannais, R. 1984. Contribucion al conocimiento de la biologia y ecologia del camaron de vega (Parastacus pugnax) en la zona de Talcahuano. Seminario de titulo, Pontificia Universidad Catolica de Chile, Sede Talcahuano, 37 pp.

Del Valle, E. 2002. Dinamica poblacional y ecologia del camaron de vega Parastacus pugnax. Tesis, Universidad Catolica del Norte, Coquimbo, 52 pp.

Dixon, W. & J. Massey. 1957. Introduction to statistical analysis. McGraw-Hill, New York, 488 pp.

Fontoura, N.F. & L. Buckup. 1989a. O crescimento do Parastacus brasiliensis (von Martens, 1869) (Crustacea, Decapoda, Parastaciade). Rev. Bras. Biol., 49(4): 897-909.

Fontoura, N.F. & L. Buckup. 1989b. Dinamica populacional e reproducao em Parastacus brasiliensis (von Martens, 1869) (Crustacea, Decapoda, Parastacidae). Rev. Bras. Biol., 49(4): 911-921.

Ibarra, M. & P. Arana. 2011. Crecimiento del camaron excavador Parastacus pugnax (Poeppig, 1835), determinado mediante tecnica de marcaje. Lat. Am. J. Aquat. Res., 39(2): 378-384.

Jara, C., E. Rudolph & E. Gonzalez. 2006. Estado de conocimiento de los malacostraceos dulceacuicolas de Chile. Gayana, 70(1): 40-49.

Keyl, F., J. Arguelles & R. Tafur. 2011. Interannual variability in size structure, age, and growth of jumbo squid (Dosidicus gigas) assessed by modal progression analysis. ICES J. Mar. Sci., 68(3): 507-518.

Kilian, E. 1959. La construccion de los tubos habitacionales del Parastacus nicoleti (Philippi). Facultad de Estudios Generales, Universidad Austral de Chile, 1: 1-7.

Martinez, A.W. & E.H. Rudolph. 2011. Records of intersexuality in the burrowing crayfish, Parastacus pugnax (Poeppig, 1835) (Decapoda, Parastacidae) with comments on the sexuality of the species of Parastacus. Crustaceana, 84(2): 221-241.

Morales-Nin, B. 1989. Growth determination of tropical marine fishes by means of otolith interpretation and length frequency analysis. Aquat. Living Resour., 2: 241-253.

Neter, J. & W. Wasserman. 1974. Applied linear statistical models. Regression, analysis of variance, and experimental designs. Editorial Richard D. Irwin, Illinois, 842 pp.

Noro, C.K. & L. Buckup. 2009. O crescimento do Parastacus defossus (Crustacea: Decapoda: Parastaciade). Zoologia, 26(1): 54-60.

Palma, S. & P. Arana. 1997. Aspectos reproductivos del langostino colorado (Pleuroncodes monodon H. Milne Edwards, 1837), frente a la costa de Concepcion, Chile. Invest. Mar., Valparaiso, 25: 203-221.

Porter, C. 1904. Materiales para la fauna carcinologica de Chile. Algunos datos sobre dos parastacidos. Rev. Chil. Hist. Nat., 8: 254-261.

Rudolph, E. 1997. Intersexualidad en el camaron excavador Parastacus pugnax (Poeppig, 1835) (Decapoda; Parastacidae). Invest. Mar., Valparaiso, 25: 7-18.

Rudolph, E. 2002. Sobre la biologia del camaron de rio Samastacus spinifrons (Philippi, 1882) (Decapoda, Parastacidae). Gayana, 66(2): 147-159.

Rudolph, E. & K. Crandall. 2005. A new species of burrowing crayfish Virilastacus rucapihuelensis (Crustacea: Decapoda: Parastacidae) from southern Chile. Proc. Biol. Soc. Wash., 118(4): 765-776.

Rudolph, E. & K. Crandall. 2007. A new species of burrowing crayfish, Virilastacus retamali (Decapoda: Parastacidae) from the southern Chile peatland. J. Crust. Biol., 27(3): 502-512.

Rudolph, E., L. de la Fuente, M.E. Van Hasselt, A. Diaz & S. Dumenes. 1991. Composicion quimica proximal de los tejidos comestibles y desperdicios de los camarones dulceacuicolas Samastacus spinifrons, Parastacus pugnax y Parastacus nicoleti (Crustacea: Decapoda: Parastacidae). Alimentos, 16(2): 23-29.

Rudolph, E., F. Retamal & A. Martinez. 2010. Cultivo de camaron de rio Samastacus spinifrons: ?una nueva alternativa para la diversificacion de la acuicultura chilena? Lat. Am. J. Aquat. Res., 38(2): 254-264.

Rudolph, E. & J. Rios. 1987. Desarrollo ontogenetico del camaron de las vegas Parastacus pugnax (Poeppig, 1835), en condiciones de laboratorio. Biota, 3: 45-58.

Sanchez, J., R. Beltran & J.P. Ramirez. 2008. Crecimiento y reproduccion del camaron Atya margaritacea (Decapoda: Atyidae) en el Rio Presidio, Sinaloa, Mexico. Rev. Biol. Trop., 56(2): 513-522.

Sanz, A. 1986. Biologia del camaron de agua dulce Palaemone teszariquieyi Sollaud, 1939 (Crustacea: Decapoda: Palaemonidae). Limnetica, 2: 293-304.

Servicio Nacional de Pesca (SERNAPESCA). 2005. Anuario estadistico de pesca. Desembarque total por especie y mes 2005. [www.sernapesca.cl].

Silva, P. & M. Spoerer. 2006. Estudio de prefactibilidad para la comercializacion de camarones de vega. Tesis Universidad de Valparaiso, Valparaiso, 177 pp.

Sparre, P. & S.C. Venema. 1997. Introduccion a la evaluacion de recursos pesqueros tropicales. FAO Doc. Tec. Pesca, 306(1): 420 pp.

Von Bertalanffy, L. 1934. Untersuchungen uber die Gesetzlichkeiten des Wachstums. 1. Allgemeine Grundlagen der Theorie. Roux' Arch-Entwicklungsmech. Org., 131: 613-653.

Received: 13 October 2011; Accepted: 10 June 2012

Mauricio A. Ibarra (1) & Patricio M. Arana (1)

(1) Escuela de Ciencias del Mar, Pontificia Universidad Catolica de Valparaiso P.O. Box 1020, Valparaiso, Chile

Corresponding author: Patricio M. Arana (parana@ucv.cl)
Tabla 1. Longitud cefalotoracica promedio mensual calculada
separadamente en machos y hembras de P. pugnax.

Table 1. Average monthly carapace length calculated separately for P.
pugnax males and females.

                       Mean carapace length (mm)

Month/year      Males   Standard    Females   Standard
                        deviation             deviation

August 2007     39.1       5.3       36.6        4.9
September       39.5       4.2       36.2        5.5
October         40.1       5.5       41.0        3.0
November        39.9       4.4       39.8        4.7
December        41.5       5.2       42.0        4.4
February 2008   40.8       5.6       40.9        4.7
March           38.8       5.5       40.2        5.7
April           42.1       5.8       40.0        5.9
Mayo            42.2       7.8       44.4        5.4
June            40.0       4.7       40.7        5.1
July            40.0       4.4       41.1        4.8
August          39.0       5.9       38.9        5.0

                        Mean carapace length (mm)

Month/year      Undetermined   Standard    Total   Standard
                               deviation           deviation

August 2007          8.7          2.2      42.0       5.7
September            9.1          1.9      38.0       5.1
October             10.1          1.3      40.5       4.5
November            11.2          2.0      39.9       4.5
December            14.9          2.3      41.7       4.9
February 2008       15.3          2.7      40.8       5.2
March                7.4          4.1      39.3       5.6
April                9.0          4.3      41.2       5.9
Mayo                 9.5          4.9      43.0       7.0
June                11.7          3.6      40.3       4.9
July                11.3          3.6      40.6       4.6
August              12.4          4.3      39.0       5.4
COPYRIGHT 2012 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 2012 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Title Annotation:articulo en ingles
Author:Ibarra, Mauricio A.; Arana, Patricio M.
Publication:Latin American Journal of Aquatic Research
Date:Jul 1, 2012
Words:4441
Previous Article:Population genetic structure revealed by a school of the freshwater migratory fish, Brycon hilarii/Estructura genetica poblacional revelada por un...
Next Article:Reproductive biology of the cominate sea catfish Occidentarius platypogon (Pisces: Ariidae) from the southeastern Gulf of California/Biologia...
Topics:

Terms of use | Privacy policy | Copyright © 2022 Farlex, Inc. | Feedback | For webmasters |