Reproductive output of the blue shrimp, Litopenaeus stylirostris (Decapoda: Penaeidae) in the Gulf of California coast at Agiabampo, Sonora-Sinalao, Mexico.ABSTRACT The reproductive period of the blue shrimp Litopenaeus stylirostris off the Gulf of California Noun 1. Gulf of California - a gulf to the west of the mainland of Mexico Sea of Cortes Mexico, United Mexican States - a republic in southern North America; became independent from Spain in 1810 coast of Sonora and Sinaloa in Mexico has been determined with the percentage of mature females as index. The objective is to determine the reproductive period and output of this species near Agiabampo, Sonora-Sinaloa by combining three indices of mature females; fecundity fecundity /fe·cun·di·ty/ (fe-kun´dit-e) 1. in demography, the physiological ability to reproduce, as opposed to fertility. 2. ability to produce offspring rapidly and in large numbers. of size, abundance and size of mature females into a single index, the egg production index (EPI EPI exocrine pancreatic insufficiency. ). Monthly samples from January through December 2002 were collected. During five continuous days around the full moon (full moon [+ or -] 2 days), trawl trawl - To sift through large volumes of data (e.g. Usenet postings, FTP archives, or the Jargon File) looking for something of interest. nets were used at depths from 1-9 m with a 2 km north and south of the mouth of the Agiabampo lagoon. The proportion of mature females to all sampled females, was highest (66%) in May, mature females were more abundant (13 [+ or -] 4 org. [ha.sup.-1]) in July, and the average total length of mature female was significantly smaller ([F.sub.(2,291)]) = 79, P < 0.05) in July than in the others months. Length at maturity was 172 mm. I concluded that it is more important to determine the reproductive processes than only the reproductive period. Particularly off Agiabampo, blue shrimp has a well-defined reproductive output of about 6 x [10.sup.6] eggs [ha.sup.-1] with just one massive spawning peak (May to July). KEY WORDS: shrimp, Litopenaeus stylirostris, reproduction, maturity, Mexico, Gulf of Mexico, Gulf of, arm of the Atlantic Ocean, c.700,000 sq mi (1,813,000 sq km), SE North America. The Gulf stretches more than 1,100 mi (1,770 km) from west to east and c.800 mi (1,290 km) from north to south. California INTRODUCTION Spawning is the base of the renewal mechanism and stock conservation of a fishery resource. Studies of reproduction of exploited penaeid resources are critical for management strategies (Garcia 1985). The core strategy is to protect the reproductive period and the reproductive areas. Most studies about reproductive period of shrimp are based on the percentage of mature females (Edwards 1978, Mathews 1981, Garduno-Argueta & Calderon-Perez 1994, Lopez-Martinez et al. 1999, Leal-Gaxiola et al. 2001). This is a biased index of population reproduction and can be modified with an index that includes fecundity-at-size data (Garcia 1985). Courtney & Masel (1997) proposed an egg production index EPI arise from those three indices. They found that this new index is a more quantitative measure of egg production in a population at a particular sampling station or sampling time. If one wants to find the most important period for population renewal, the studies of the reproductive biology of shrimp must take into account more than just reproductive percentage of mature female. This may be considered a gonad gonad /go·nad/ (go´nad) a gamete-producing gland; an ovary or testis.gonad´algonad´ial indifferent gonad the sexually undifferentiated gonad of the early embryo. index, egg production for the population among others (Oh & Hartnoll 1999). In the Mexican Pacific shrimp fishery A shrimp fishery is a fishery directed toward harvesting either shrimp or prawns. Fisheries do not generally distinguish between the two taxa, and the terms are used interchangeably. This article therefore refers to the catching of either shrimp or prawns. , the blue shrimp Litopenaeus stylirostris (Stimpson, 1874) comprises 99% of the total shrimp catch in coastal lagoons southern Sonora (Garduno-Argueta 1974, Marquez-Tiburcio 1976, Magallon-Barajas 1987, Arreola-Lizarraga 1995). Reproductive studies of L. stylirostris determined that the area near the coastal lagoon's mouths as the primary spawning zone (Mathews 1981, Garduno-Argueta & Caledron-Perez 1994). Mexican fisheries laws now prohibit any catch from coastline to 9-m depth and within 2 km south and north of the lagoon's mouths. Fecundity of blue shrimp has been described with a power equation with a value around 3 (Garcia-Gomez 1976, Rodriguez de la Cruz de la Cruz is a common surname in the Spanish language meaning 'of The Cross.'
MATERIAL AND METHODS Study Area The Agiabampo coastal lagoon (Lat (Local Area Transport) A communications protocol from Digital for controlling terminal traffic in a DECnet environment. LAT - Local Area Transport . 26[degrees]07' to 26[degrees]29'N, Long. 109[degrees]05' to 109[degrees]20'W; Fig. 1) is a relatively long and narrow barrier lagoon created by longshore long·shore adj. Occurring, living, or working along a seacoast. [Short for alongshore.] currents. The broad region has a subtropical sub·trop·i·cal adj. Of, relating to, or being the geographic areas adjacent to the Tropics. subtropical Adjective of the region lying between the tropics and temperate lands hot desert (BWh) climate (Garcia 1988) and the average sea surface temperature Sea surface temperature (SST) is the water temperature at the surface. In practical terms, the exact meaning of "surface" will vary according to the measurement method used. is 30.4[degrees]C in July and 19.5[degrees]C in January. [FIGURE 1 OMITTED] Sampling From January to December 2002, shrimp samples were taken each month for five continuous days (full moon [+ or -] 2 days). Collection was done with small boats, about 7 m long. Trawl nets with 15 m mouth and 32 mm mesh were used. Tows were made for 15 min every 1.5 h at flood and ebb tides. This was done at depth from 1-9 m at locations ranging up to 2 km north and south of the mouth of the coastal lagoon (Fig. 1). Sex, gonadal gonadal pertaining to or arising from a gonad. See also testicular, ovarian. gonadal cords cords formed by epithelial cells which migrate from the mesonephric tubules in the embryo to the gonadal ridge and establish the indifferent maturity and total length (tip of the rostrum rostrum /ros·trum/ (ros´trum) pl. ros´tra, rostrums [L.] a beak-shaped process. ros·trum n. pl. ros·trums or ros·tra A beaklike or snoutlike projection. to tip of the telson tel·son n. 1. The rearmost segment of the body of certain arthropods. 2. An extension of this segment, such as the middle lobe of the tail fan of a lobster or the stinger of a scorpion. ) [+ or -] 1 mm of the samples were determined. Degree of gonad maturity was determined with the four phases of the morphochromatic scale, comprising four stages (Garcia-Gomez 1976). For this study, specimens were grouped into immature (Stages I and II) and mature (Stages III and IV) categories. The percent distribution of mature females over the sampling period was determined. Size structure of mature females was obtained by grouping every 5-mm interval from 120 to 240 total length (TL). Abundance of mature females was determined as specimens per hectare. This was done using a sweeping area described in Sparre & Venema (1995). Satellite geo-positioning devices locate the beginning and ending position of each trawl. I divided the number of mature females by the calculated area (in hectares). Fecundity-at-size was determined by the equation proposed by Garcia-Gomez (1976): Eggs = 0.0007[L.sup.3.9439] where L is total length of the mature female. Egg production index (EPI), similar to one proposed by Courtney and Masel (1997) was determined by combining size structure, fecundity-at-size and abundance of mature females. The EPI is formed as follows: EPI = [n.summation over (i=1)] (0.0007[L.sub.ci.sup.3.9439])(P[L.sub.ci]a) where i is the ith size class, [L.sub.ci] = is the value of length of class i, P[L.sub.ci] proportion of class i in a particular month, and a is the abundance of mature female in particular month. The relationship of length at maturity uses a transformation: [MATHEMATICAL EXPRESSION A group of characters or symbols representing a quantity or an operation. See arithmetic expression. NOT REPRODUCIBLE IN ASCII ASCII or American Standard Code for Information Interchange, a set of codes used to represent letters, numbers, a few symbols, and control characters. Originally designed for teletype operations, it has found wide application in computers. .] (King, 1995, pp. 112-115; 158-160) to yield: ln ([1 - P]/P) = r[L.sub.m] - rL where P is the proportion of length of mature female, r is the curve slope, [L.sub.m] is the length at first maturity or length at which correspond 50% of ovigerous females and L is total length. I then plotted: ln([1 - P]/P) against L and, using stepwise stepwise incremental; additional information is added at each step. stepwise multiple regression used when a large number of possible explanatory variables are available and there is difficulty interpreting the partial regression linear regression Linear regression A statistical technique for fitting a straight line to a set of data points. to obtain values for a and b later I obtained: r = -b and Lm = a/r. RESULTS A female:male ratio of 6:5 was obtained from 1,512 specimens (825 females/687 males). For mature specimens, the ratio was 1:2. The blue shrimp Litopenaeus stylirostris is present year round off in coastal waters near Agiabampo, higher frequency of both sexes being May to September (Fig. 2). [FIGURE 2 OMITTED] Period of Sexual Maturity The percentage of mature males was over 95% during the entire sampling period (Fig. 3), except for January. With this result, I took only the percentage of mature females to define the reproductive period of the blue shrimp off Agiabampo, Sonora-Sinaloa, I found only one period (May through July) in which the percentage of mature females was close to or greater than 50% (Fig. 3). The other months in which mature females appear were January (13%) and August (11%). [FIGURE 3 OMITTED] Frequency of Sizes Total length of mature males ranged from 95-220 mm, averaging 173 [+ or -] 1.5 mm and a 12% coefficient of variation Coefficient of Variation A measure of investment risk that defines risk as the standard deviation per unit of expected return. . Total length of mature females for the entire study period was 105-235 ram, averaging 173 [+ or -] 2 mm with a 15% coefficient of variation. Male and female sizes were no different ([F.sub.(1, 1510)] = 0.014, P = 0.9). Frequency of total length group for May to July is shown in Figure 4. The modal size shows a decreasing tendency from May to July (Fig. 4.). Total length was significantly smaller in July ([F.sub.(2, 291)] = 79, P < 0.05). No significant differences were found in May and June (Fig. 5). TL values were 201 [+ or -] 3 mm, 195 [+ or -] 4 mm and 169 [+ or -] 4 mm for May, June and July, respectively. [FIGURES 4-5 OMITTED] Abundance By the sweeping area method, I used the months in which mature females were caught to determine relative abundance. On average ([+ or -] confidence interval confidence interval, n a statistical device used to determine the range within which an acceptable datum would fall. Confidence intervals are usually expressed in percentages, typically 95% or 99%. , 95%) 5 [+ or -] 1 females per hectare were caught in May. In June, it was 8 [+ or -] 2 females per hectare and in July 13 [+ or -] 4 females per hectare. Abundance was negligible in August and January (Fig. 5). The EPI in eggs x [ha.sup.-1] was similar in these 3 summer months (May, June and July). Figure 5 shows higher and larger size of mature females in May, but higher average abundance of mature females occurred in July. These results highlight the importance of using more than a single index to determine reproductive period for blue shrimp. Size at maturity or size at massive maturation was calculated to be 172 mm of the total length (Fig. 6). [FIGURE 6 OMITTED] DISCUSSION The reproductive period of blue shrimp off the coast of the Agiabampo coastal lagoon, is well defined as late spring through early summer. In previous studies, the reproductive period of blue shrimp occurred from March to September, with a peak from May to June and shortening in length from south to north. Garduno-Argueta & Calderon-Perez (1994) and Edwards (1978) found March to September, with a June peak off Mazatlan. Off Guaymas, March through August, with a peak in June, was found by Garcia-Gomez (1976); off Puerto Penasco, April through August, with a peak in May, was found by Mathews (1981). These studies only used the percentage of mature females as an index of the reproductive period. Because the percentage of mature females is a biased index of population reproduction (Garcia 1985), I combined this index with abundance, fecundity and size structure of mature females. No studies were found that established a relationship among these three indices for blue shrimp, but for other penaeid shrimp, it has already been used (Garcia 1985, Courtney & Masel 1997, Oh & Hartnoll, 1999). Combining three indices, I found in this study that the total massive reproduction period is May through July. And not only May in which month I found 66% of mature female. The peak months of reproduction mentioned in previous studies reported 90% (Guaymas and Penasco) and 66% (Mazatlan) mature females. Caution must be taken with those results because of the limited measurement to account for an index of the reproductive period. I see a difference between zones, longer off Mazatlan and shorter off Puerto Penasco. The difference can be explained by the variance in sea surface temperature (SST SST: see airplane. ). Soto-Mardones et al. (1999) analyzed the SST of the entire Gulf of California and found a greater range of SSTs between seasons, with this range increasing northward, Between spring and summer, the SST difference off Mazatlan is 7[degrees]C, and off Puerto Penasco 11[degrees]C. Agiabampo is located between Mazatlan and Puerto Penasco, but the SST differences between spring and summer are the same as those off Puerto Penasco. Soto-Mardones et al. (1999) did not find statistical differences in SST from July to September in the entire Gulf of California, but average SST in Mazatlan in March is similar to that found in May in Puerto Penasco. This could be the basis for differences in length of the reproductive period among zones because it is clearly observed that in the period of peak reproduction, the SST is not different. I found a higher percentage (66%) and larger average size 201 [+ or -] 3 mm of the mature females in May. But July has the higher abundance of mature female. These results clearly show that we need to use at least two other indices and not just the percentage of the mature females. Size at maturity was 172 mm TL and is very similar with that reported for this species off Guaymas and Puerto Penasco, 175 mm TL (Mathews 1981). This size is larger than what is caught with fishing commercial gear, suggesting that most of the females have no chance to reproduce at least once before being caught. This would induce recruitment overfishing Overfishing occurs when fishing activities reduce fish stocks below an acceptable level. This can occur in any body of water from a pond to the oceans. More precise biological and bioeconomic terms define 'acceptable level'. , as Gracia (1996) found in the Gulf of Mexico Noun 1. Gulf of Mexico - an arm of the Atlantic to the south of the United States and to the east of Mexico Golfo de Mexico Atlantic, Atlantic Ocean - the 2nd largest ocean; separates North and South America on the west from Europe and Africa on the east with the related shrimp Litopenaeus setiferus (Linnaeus, 1767). No report of recruitment overfishing had been proposed for L. stylirostris, but since 1976, the size at maturity had been larger than the commercial catch size. This highlights the importance of understanding reproduction processes and not only the reproduction period. If recruitment overfishing is occurring, serious problems for population recovery are likely. I conclude that the appropriate combination of indices include percentage of mature females, abundance of mature females, and fecundity-at-size to determine the reproductive period of blue shrimp. These three indices for the blue shrimp off Agiabampo showed a single maturation period from May to July that must be managed properly to maintain a sustainable fishery. ACKNOWLEDGMENTS The author thanks Araceli Ramos-Montiel and Rufino Morales-Azpeitia. This study was supported by contract 908-1G of the Instituto Nacional de la Pesca La Pesca is a small town in the Mexican state of Tamaulipas. It is located on the Gulf of Mexico, at the mouth of the Río Soto La Marina, between the Laguna Madre to the north and the Laguna Morales to the south. (INP INP abbr. International News Photo ) and CIBNOR. The "Sylvia Ramirez" fisheries cooperative society cooperative society Noun a commercial enterprise owned and run by customers or workers, in which the profits are shared among the members provided logistic support Noun 1. logistic support - assistance between and within military commands logistic assistance support - the activity of providing for or maintaining by supplying with money or necessities; "his support kept the family together"; "they gave him emotional for field sampling. Technical personnel of INP and the CIBNOR Guaymas Unit helped with the laboratory and fieldwork. The editor at CIBNOR improved the English text. LITERATURE CITED Arreola-Lizarraga, J. A. 1995. Diagnosis ecologica de Bahia de Lobos, Sonora, Mexico. Master thesis. La Paz La Paz, city, Bolivia La Paz (lä päs), city (1992 pop. 713,378), W Bolivia, administrative capital (since 1898) and largest city of Bolivia. The legal capital is Sucre. , Mexico. 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Biol. Ann. Rev. 16:145-180. Garcia, E. 1988. Modificacion al sistema de clasificacion climatica de Koppen para adaptarlo a las condiciones de la Republica Mexicana. Mexico: Offset Larios. 222 pp. Garcia, S. 1985. Reproduction, stock assessment models and population parameters in exploited Penaeid shrimp populations. In: P. C. Rothlisberg, B. J. Hill & D. J. Staples, editors. Second Australian National Prawn Seminal. Cleveland, Australia. NPS NPS National Park Service NPS Naval Postgraduate School NPS Net Promoter Score (customer management) NPS Non-Point Source pollution NPS Native Plant Society NPS Norfolk Public Schools (Virginia) 2. pp. 139-158. Garcia-Gomez, M. 1976. Fecundidad del camaron cafe Penaeus californiensis y del camaron azul Penaeus stylirostris Puerto Penasco y Guaymas, Sonora. In: INP-FAO editors. Memorias del Simposio sobre biologia y Dinamica Poblacional de Camarones. Guaymas, Sonora, Mexico: S.I.C. Subsecretaria de Pesca, Instituto Nacional de Pesca, vol. 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The La Costa Resort and Spa sur de Sinaloa, Mexico. Rev. Inv. Cient. UABCS Serie Cienc. Mar. 1:27-34. Garduno-Argueta, H. 1974. La explotacion de los recursos pesqueros en el litoral de la zona reservada a la tribu La Tribu is a Quebec-based record label. Noted artists
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King, M. 1995. Fisheries biology, assessment and management. Victoria, Australia: Fishing News Books. 341 pp. Leal-Gaxiola, A., J. Lopez-Martinez, E. A. Chavez, S. Hernandez-Vazquez & F. Mendez-Tenorio. 2001. Interannual variability of reproductive period of the brown shrimp, Farfantepenaeus californiensis (Holmes, 1900) (Decapoda, Natantia). Crustaceana 74(9):839-851. Lopez-Martinez, J., F. Garcia-Dominguez, E. Alcantara-Razo & E. A. Chavez. 1999. Periodo reproductivo y talla de madurez masiva del camaron de roca Sicyonia penicillata (Decapada: Sicyonildae) en Bahia Kino kino the juice of certain plants, some tropical and some Australian eucalypts, used in medicine as an astringent. , Sonora, Mexico. Rev. Biol. Trop. 47(1-2):109-117. Magallon-Barajas, F. J. 1987. The Pacific shrimp fishery of Mexico. CalCOFI Rep. 27:43-52. Marquez-Tiburcio, M. A. 1976. Captura y esfuerzo en pesquerias de camaron en aguas interiores (Bahia Guasimas y Lobos, Sonora). In: INP-FAO editors. Memorias del Simposio sobre biologia y Dinamica Poblacional de Camarones. Guaymas, Sonora, Mexico. S.I.C. Subsecretaria de Pesca, Instituto Nacional de Pesca, vol. I. pp. 47-57. Mathews, C. P. 1981. A review of the North American North American named after North America. North American blastomycosis see North American blastomycosis. North American cattle tick see boophilusannulatus. penaeid fisheries, with particular reference to Mexico. Kuwait Bull. Mar. Sci. 2:325-409. Oh, C. W. & R. G. Hartnoll. 1999. Size at sexual maturity, reproductive output, and seasonal reproduction of Philocheras trispinosus (Decapoda) in Port Erin Coordinates: Port Erin (Manx: Purt Chiarn) is a town in the south of the Isle of Man. Its population is 3,369 according to the 2001 census. The name means either Lord's Port or Iron Port. Bay, Isle of Man Noun 1. Isle of Man - one of the British Isles in the Irish Sea Man British Isles - Great Britain and Ireland and adjacent islands in the north Atlantic . J. Crustacean crustacean (krŭstā`shən), primarily aquatic arthropod of the subphylum Crustacea. Most of the 44,000 crustacean species are marine, but there are many freshwater forms. Biol. 19(2):252-259. Rodriguez de la Cruz Ramirez, M. C. 1981. Aspectos pesqueros del camaron de alta mar en el Pacifico mexicano. Cienc. Pesq. 1(2):1-19. Soto-Mardones, S., S. G. Marinone & A. Pares-Sierra. 1999. Variabilidad espacio temporal de la temperatura superficial del Mar Del Mar is the name of several places in the United States of America:
Sparre, P. & S. C. Venema. 1995. Introduccion a la evaluacion de recursos pesqueros tropicales. Parte 1. Manual. FAO FAO, n See Food and Agriculture Organization. Documento Tecnico de Pesca no. 306.1 Rev. 440 pp. EUGENIO ALBERTO ARAGON-NORIEGA Centro de Investigaciones Biologicas del Noroeste (CIBNOR). Unidad Guaymas. Km 2.35 Camino al Tular, Estero de Bacochibampo. Guaymas, Sonora, 85454, Mexico Corresponding author. E-mail: aaragon04@cibnor.mx |
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