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Long-term variations in population structure, growth, mortality, exploitation rate, and recruitment pattern of two major commercial small pelagic fishes (CSPFs) (Decapterus maruadsi and Trachurus japonicus) are reported based on bottom trawl survey data collected during 2006-2020 in the Beibu Gulf, South China Sea. All individuals collected during each sampling quarter over a period of 15 years were subjected to laboratory-based analysis. In this study, the stock of D. maruadsi and T. japonicus inhabiting the Beibu Gulf was assessed using length-based methods (bootstrapped electronic length frequency analysis (ELEFAN)) to complete stock assessment in different fishery management periods (the division of fisheries management periods was based on China's input and output in the South China Sea offshore fisheries over 15 years, specifically divided into period I (2006-2010), period II (2011-2015), and period III (2016-2020)). The results showed that the mean body length, dominant body size, and estimated asymptotic length of two CSPFs decreased, whereas their growth coefficient decreased, indicating miniaturization and slower growth, respectively. Estimated exploitation rates and catching body length for two CSPFs indicated that both stocks in the Beibu Gulf were overexploited in period I and moderately exploited after 2011. These stocks were taking a good turn in status in period III, with the exploitation rate much lower than the initial period and reversing the downward trend in catching body length. Furthermore, the variations in the spawning season of the two CSPF stocks and their barely satisfactory expected yield indicated the complexity of the current fishery management in the Beibu Gulf. These results suggest that management measures to reduce fishing pressure may have a positive influence on the biological characteristics of those CSPFs in the Beibu Gulf; however, the stock structure already affected by overfishing will be a huge challenge for the conservation and restoration of fisheries resources in the future. Given that the current stocks of D. maruadsi and T. japonicus in the Beibu Gulf still have low first-capture body length (Lc) and high fishing mortality (F) (compared to F0.1), we identify a need to refine population structure by controlling fishing efforts and increasing catchable size, and more consideration should be given to the local fishery resource status in fisheries management.

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Population's biological parameters, including length at first capture, mortalities, exploitation rates, growth coefficient, longevity, and recruitment times, are essential in assessing fishing status, but there is no data on Mystus mysticetus. Therefore, the study was conducted to provide these parameters to assess the fishing status of this species at Cai Rang, Can Tho (CRCT) and Long Phu, Soc Trang (LPST). A collection of 741 individual fish was used for analysis and showed that most fish size groups ranged from 9.0 cm to 12.0 cm, and the asymptotic length was 16.8 cm for both CRCT and LPST populations. The fish population von Bertalanffy curve was L t = 16.80(1 - e-0.51(t + 0.38)) at CRCT and L t = 16.80(1 - e-0.48(t + 0.40)) at LPST. The fish growth coefficient at CRCT (2.16) was higher than at LPST (2.13), whereas the reverse case was true for longevity ranging from 5.88 years (at CRCT) to 6.25 years (at LPST). At CRCT, fishing mortality, natural mortality, total mortality, and exploitation rate were 0.69/year, 1.40/year, 2.09/year, and 0.33, respectively; at LPST, these values were 0.75/year, 1.33/year, 2.08/year, and 0.36, respectively. Although the population parameter of this fish species exhibited a spatial variation, both CRCT and LPST fish resources have not been subjected to overexploit because E (0.33 at CRCT and 0.36 at LPST) is lower than E 0.1 (0.707 at CRCT and 0.616 at LPST).

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Ellochelon vaigiensis is widely distributed and plays a vital role in the fisheries in the Mekong Delta (MD), but data on its population biological traits have not been known. Consequently, this study was conducted to provide data on its population biology used for fishing status assessment and fish resources management. Fish specimens were collected using trawl nets in two regions of the Hau River mouth, including northern in Ben Tre and Tra Vinh (BTTV) and southern in Soc Trang and Bac Lieu (STBL). Fish population biological parameters were estimated using FiSAT II software based on the fish length-frequency data. The male and female length-frequency data in each ecoregion were pooled together. Data analysis of 1,383 individual fish showed the sex ratio of the species was 1.00:1.30 at BTTV (309 females and 402 males) and 1.00:1.25 STBL (299 females and 373 males). Most fish specimens were caught at 12-22 cm total length (914 individuals), accounting for 66.09% of the fish collection. The difference in salinity between these two regions could affect the population biological parameters of E. vaigiensis. There were five cohorts (e.g., five growth curves) in the BTTV and STBL. The von Bertalanffy curves of fish populations at BTTV and STBL were L = 33.6 (1 -e -0.46(t + 0.34)) L = 31.5 (1 -e -0.56(t + 0.29)), respectively. The growth index (Φ') of this species at STBL (2.74) was higher than that at BTTV (2.72), whereas its longevity at BTTV (6.52 yrs) was higher than at STBL (5.36 yrs). The biomass and relative yield parameters, including E 0.1, E 0.5 and E max were 0.358, 0.265 and 0.436 at BTTV; and 0.418, 0.293, and 0.513 at STBL, respectively. The fishing (F), natural (M), and total (Z) mortalities were 0.35/yr, 1.06/yr, and 1.41/yr at BTTV; and 0.55/yr, 1.24/yr, and 1.78/yr at STBL, respectively. The BTTV and STBL population was not overexploited because the exploitation rate (E BTTV = 0.25, E STBL = 0.31) was lower than E 0.1 (0.358 in BTTV and 0.418 in STBL).

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The population structure of Protosalanx chinensis is affected by a variety of factors, including water environment, intraspecific differentiation, interspecific competition and commercial fishing. To investigate the growth performance and the current status of resource utilization of P. chinensis in two important fish farming grounds (Dalong Lake and Amuta Lake) in Daqing, Northeast China, we collected 1513 P. chinensis samples from April to December 2018 for measurement and recording the basic biological characteristics. We estimated the parameters including population growth, mortality and exploitation using Von Bertalanffy growth formula, Beverton-Holt model, Pauly's empirical formula and length-based Bayesian biomass estimation method. The results showed that the asymptotic body lengths of Dalong Lake (n=660) and Amuta Lake (n=853) populations were 183.75 and 169.10 mm, respectively. The growth performance indices were both 4.85, and the body mass growth equations were Wt=29.29×(1-e-2.1(t+0.07))3.2977 and Wt=28.72×(1-e-2.5(t+0.07))3.4168, respectively. The ages at inflection were 0.49 a and 0.43 a, and the condition factors were 5.30×10-4±1.38×10-4 and 4.00×10-4±1.61×10-4. The exploitation rates were 0.60 and 0.61, and the relative catch per unit of supplementation were 0.069 and 0.075, respectively. The current differences in population resources between Dalong Lake and Amuta Lake in Daqing were mainly manifested in the parameters related to growth characteristics. The main reason for such differences was changes in the survival conditions of P. chinensis populations after the period of dietary transition induced by the density differences.

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BACKGROUND: Population dynamics are driven by a number of biotic (e.g., density-dependence) and abiotic (e.g., climate) factors whose contribution can greatly vary across study systems (i.e., populations). Yet, the extent to which the contribution of these factors varies across populations and between species and whether spatial patterns can be identified has received little attention. METHODS: Here, we used a long-term (1982-2011), broad scale (182 sites distributed across metropolitan France) dataset to study spatial patterns in the population's dynamics of three freshwater fish species presenting contrasted life-histories and patterns of elevation range shifts in recent decades. We used a hierarchical Bayesian approach together with an elasticity analysis to estimate the relative contribution of a set of biotic (e.g., strength of density dependence, recruitment rate) and abiotic (mean and variability of water temperature) factors affecting the site-specific dynamic of two different size classes (0+ and >0+ individuals) for the three species. We then tested whether the local contribution of each factor presented evidence for biogeographical patterns by confronting two non-mutually exclusive hypotheses: the "range-shift" hypothesis that predicts a gradient along elevation or latitude and the "abundant-center" hypothesis that predicts a gradient from the center to the edge of the species' distributional range. RESULTS: Despite contrasted life-histories, the three species displayed similar large-scale patterns in population dynamics with a much stronger contribution of biotic factors over abiotic ones. Yet, the contribution of the different factors strongly varied within distributional ranges and followed distinct spatial patterns. Indeed, while abiotic factors mostly varied along elevation, biotic factors-which disproportionately contributed to population dynamics-varied along both elevation and latitude. CONCLUSIONS: Overall while our results provide stronger support for the range-shift hypothesis, they also highlight the dual effect of distinct factors on spatial patterns in population dynamics and can explain the overall difficulty to find general evidence for geographic gradients in natural populations. We propose that considering the separate contribution of the factors affecting population dynamics could help better understand the drivers of abundance-distribution patterns.

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Developing-world shark fisheries are typically not assessed or actively managed for sustainability; one fundamental obstacle is the lack of species and size-composition catch data. We tested and implemented a new and potentially widely applicable approach for collecting these data: mandatory submission of low-value secondary fins (anal fins) from landed sharks by fishers and use of the fins to reconstruct catch species and size. Visual and low-cost genetic identification were used to determine species composition, and linear regression was applied to total length and anal fin base length for catch-size reconstruction. We tested the feasibility of this approach in Belize, first in a local proof-of-concept study and then scaling it up to the national level for the 2017-2018 shark-fishing season (1,786 fins analyzed). Sixteen species occurred in this fishery. The most common were the Caribbean reef (Carcharhinus perezi), blacktip (C. limbatus), sharpnose (Atlantic [Rhizoprionodon terraenovae] and Caribbean [R. porosus] considered as a group), and bonnethead (Sphyrna cf. tiburo). Sharpnose and bonnethead sharks were landed primarily above size at maturity, whereas Caribbean reef and blacktip sharks were primarily landed below size at maturity. Our approach proved effective in obtaining critical data for managing the shark fishery, and we suggest the tools developed as part of this program could be exported to other nations in this region and applied almost immediately if there were means to communicate with fishers and incentivize them to provide anal fins. Outside the tropical Western Atlantic, we recommend further investigation of the feasibility of sampling of secondary fins, including considerations of time, effort, and cost of species identification from these fins, what secondary fin type to use, and the means with which to communicate with fishers and incentivize participation. This program could be a model for collecting urgently needed data for developing-world shark fisheries globally. Article impact statement: Shark fins collected from fishers yield data critical to shark fisheries management in developing nations.

Uso de Aletas Secundarias Proporcionadas por Pescadores para Llenar Vacíos Importantes de Información sobre las Pesquerías de Tiburones Resumen Con frecuencia no se evalúan las pesquerías de tiburones del mundo en desarrollo ni cuentan con un manejo activo de sustentabilidad. Uno de los principales obstáculos para esto es la falta de información sobre las especies y la composición de los tamaños en las capturas. Probamos e implementamos una estrategia nueva y potencialmente aplicable en todas partes para la recolección de estos datos: la entrega obligatoria de las aletas secundarias de bajo valor económico (aletas anales) obtenidas de los tiburones desembarcados por parte de los pescadores y el uso de estas aletas para reconstruir las especies y tamaños en la captura. Usamos identificaciones genéticas de bajo costo e identificaciones visuales para determinar la composición de las especies y aplicamos una regresión lineal a la longitud total y a la de la base de la aleta anal para la reconstrucción del tamaño en captura. Probamos la viabilidad de esta estrategia en Belice, primero en un estudio de prueba de concepto y después subiendo al nivel nacional para la temporada de pesca de tiburón 2017-2018 (1,786 aletas analizadas). Se registraron 16 especies en esta pesquería. Las más comunes fueron Carcharhinus perezi, C. limbatus, Rhizoprionodon terraenovae y R. porosus (consideradas como un grupo) y Sphyrna cf. tiburo. Las últimas tres especies fueron desembarcadas principalmente por encima del tamaño maduro, mientras que con las dos primeras especies lo hacían por debajo del tamaño maduro. Nuestra estrategia demostró ser efectiva en la obtención de información crítica para el manejo de la pesquería de tiburones y sugerimos que las herramientas desarrolladas como parte de este programa puedan ser exportadas a otras naciones en esta región y aplicadas casi de manera inmediata si existen los medios para comunicarse con los pescadores e incentivarlos a proporcionar las aletas anales. Fuera del Atlántico Occidental tropical, recomendamos una mayor investigación de la viabilidad del muestreo de aletas secundarias, incluyendo la consideración del tiempo, esfuerzo y costo de la identificación de especies a partir de estas aletas; cuál tipo de aleta secundaria utilizar; y los medios mediante los cuales comunicarse con los pescadores e incentivarlos a participar. Este programa podría ser un modelo para la recolección de información de necesidad urgente para las pesquerías del mundo en desarrollo.

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The shape of the length frequency distribution (LFD) is an important input for stock assessments and one of the most important features in studies of fish population dynamics, providing estimates of growth parameters. In practice, oversampling may occur when sampling commercially important species. At times of more and more limited resources, the length sample size can be optimized at some stages of national or regional sampling programmes, without reducing the quality of stock assessments. The main objective of this study is to demonstrate a general distribution-free methodological approach for an optimization of sample size developed as an alternative to both analytical and bootstrap approaches. A novel framework to identify the reduced but still informative sample and to quantify the (dis) similarity between reduced and original samples is proposed. The identification procedure is based on the concept of reference subsample, which represents a theoretical minimal representative subsample that despite smaller sample size still preserves a reasonably precise LFD for certain species. The difference between the original sample and the reference subsample called admissible dissimilarity value (ADV) serves as the upper threshold and can be used to quantify the reliability of derived subsamples. Monte Carlo simulations were conducted to validate the approach under various LFD shapes. We illustrate in case studies how ADV can support to evaluate adequate sampling effort. The case studies focus on length samples from the German commercial vessels fishing for North Sea cod (Gadus morhua).

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Management procedures (MPs) based on data-limited methods (DLMs) recently developed to give management advices for data-limited stocks worldwide are scarce or yet to be implemented on freshwater species. In this study, case studies (CSs) were developed using length-frequency data (LFD) of common carp species harvested from Dianshan Lake to estimate life-history parameters from existing methods. These CSs were later used to examine their influences when tested with various MPs under scenarios when operating models (OMs) were subjected to observation and estimation uncertainties. The results after management strategy evaluation (MSE) was run for various defined OMs showed that three MPs emerged best for providing managing advice. For high yield to be maintained during short-term periods, MinlenLopt1 suggested the smallest length at full retention (sLFR) to be 42.11 cm; while Slotlim and matlenlim2 suggested that to maintain biomass and stable spawning biomass (SBMSY) and also avoid overfishing from occurring in this fishery, sLFR should be 56.1 cm. Values given by these MPs allowed the removal of species that spawned at least once. Also, life-history parameters derived from CS4 presented the best results, being more reliable in presenting better inputs for effective management of the said fishery.

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The Indian river shad, Gudusia chapra (Hamilton, 1822), is a commercially important freshwater clupeid that contribute to the livelihood of subsistence and marginal fisheries in inland open waters of India and its adjacent countries. The present study was carried out on the growth and mortality of Indian River shad, Gudusia chapra (Hamilton, 1822) based on the commercial length-frequency data collected monthly during October 2014 to September 2015 of a large reservoir located in the border of Jharkhand and West Bengal. The ELEFAN-I (Electronic Length Frequency Analysis) module in FiSAT (FAO-ICLARM Stock Assessment Tools) was used for estimation of growth parameters (L∞, K). The total mortality was estimated following Pauly (ICLARM Fishbyte 2(1):9-13, Pauly 1983) whereas exploitation ratio and maximum sustainable yield were calculated following Gulland (1979). The asymptotic length (L∞) and growth coefficient (K) were estimated as 194 mm and 1.23 year-1, respectively. The species grows to 141.56 and 182.91 mm at the end of the 1st and 2nd years of life. The total natural and fishing mortalities were 6.63, 2.45 and 4.18 year-1 respectively. The value of growth performance index was 2.69. The exploitation ratio (E) was estimated as 0.63. As the exploitation ratio (E) is slightly beyond the optimum, there is likelihood of some threat of overexploitation. Though recruitment was continuous, major pulse was observed during April-May. The present investigation is a first report from Indian reservoir. The maximum sustainable yield of this species was estimated as 485.6 t against the present annual yield of 612.3 t. Avoiding overfishing and wise use of available resources are of prime importance for sustainable fishery management of the reservoir.

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Understanding how aquatic species grow is fundamental in fisheries because stock assessment often relies on growth dependent statistical models. Length-frequency-based methods become important when more applicable data for growth model estimation are either not available or very expensive. In this article, we develop a new framework for growth estimation from length-frequency data using a generalized von Bertalanffy growth model (VBGM) framework that allows for time-dependent covariates to be incorporated. A finite mixture of normal distributions is used to model the length-frequency cohorts of each month with the means constrained to follow a VBGM. The variances of the finite mixture components are constrained to be a function of mean length, reducing the number of parameters and allowing for an estimate of the variance at any length. To optimize the likelihood, we use a minorization-maximization (MM) algorithm with a Nelder-Mead sub-step. This work was motivated by the decline in catches of the blue swimmer crab (BSC) (Portunus armatus) off the east coast of Queensland, Australia. We test the method with a simulation study and then apply it to the BSC fishery data.

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The Gorean snapper, Lutjanus goreensis is an important component of artisanal fisheries and trawl landings in the Gulf of Guinea. Despite its economic importance, there is a dearth of information on size structure and life history strategies of the species. Therefore, the objectives of this study were to provide baseline data on the life stages, exploitation status and habitat use for the species in Nigeria. Monthly samples were obtained from artisanal and trawl catches in Five Cowrie Creek and Lagos coastal waters between December 2008 and December 2010, respectively. Length-frequency distributions of the fishes caught were analysed to provide preliminary information on mean and modal lengths at capture and life - history strategies based on habitat use and estuarine-dependency for L. goreensis. A total of 822 specimens of L. goreensis were collected from Five Cowrie Creek while 377 specimens were collected from Lagos coastal waters. Total length varied between 7.90-34.90cm for creek samples and from 21.90-56.10cm for marine samples. Length-frequency histograms showed polymodal size distributions in creek and marine samples. Length-frequency distributions of L. goreensis showed a high abundance of juveniles (<20cm) and sub-adults (20-35cm) which accounted for 84.1% and 68.4% of creek and marine samples examined, respectively. For the creek samples, fish in modal length class of 13.00-13.99cm were the most exploited while in the marine samples, length classes of 29.00-30.99cm and 31.00-32.99cm constituted the most frequently exploited fishes. Increase in total lengths from the creek (mean±SD; 16.19±3.73cm) to the marine habitat samples (32.89±6.14cm) indicated ontogenetic shift in habitat use. Occurrence of a predominant juvenile population in Five Cowrie Creek by L. goreensis suggests estuarine-dependency and is indicative of a temporary juvenile habitat or a migratory corridor. In conclusion, data from the presently reported study and previous studies demonstrated that juvenile L. goreensis displays estuarine dependency and habitat flexibility. Hence, this underscores the importance of preserving estuarine environments as essential fish habitats to prevent overfishing. The study also concludes that the species is vulnerable to recruitment overfishing in the marine environment especially as a consequence of shrimping. Consequently, it advocates for ban on all fishing activities during peak spawning periods in breeding grounds and shrimp ground assemblage.

El pargo Lutjanus goreensis es un componente importante de la pesca artesanal y de arrastre en el Golfo de Guinea. A pesar de su importancia económica, hay una escasez de información sobre la estructura de tamaño y las estrategias de historia de vida de las especies. Por lo tanto, los objetivos de este estudio fueron proporcionar datos de referencia sobre las etapas del ciclo de vida, el estado de la explotación y el hábitat de la especie en Nigeria. Se realizaron recolectas mensuales de capturas artesanales y de arrastre en Five Cowrie Creek y aguas costeras de Lagos en diciembre 2008 y diciembre 2010, respectivamente. Se analizaron las distribuciones de frecuencia de tallas de los peces capturados para proporcionar información preliminar sobre la media y longitudes modales en la captura y las estrategias de historia de vida basado en el uso del hábitat y la dependencia a los estuarios para L. goreensis. Un total de 822 ejemplares de L. goreensis se obtuvieron de Five Cowrie Creek, mientras que 377 muestras de las aguas costeras de Lagos. La longitud total varió entre 7.90-34.90cm para muestras del estuario y 21.90-56.10cm para marinas. Histogramas de frecuencia de talla mostraron distribuciones de tamaño polimodales en muestras estuarinas y marinas. Distribuciones de frecuencia de talla de L. goreensis mostraron una alta abundancia de juveniles (<20cm) y subadultos (20-35cm) que representaron el 84.1% y el 68.4% de los estuarios y las muestras marinas examinadas respectivamente. Para las muestras del estuario, peces de talla 13.00-13.99cm fueron los más explotados, mientras que en muestras marinas, las tallas de 29.00-30.99cm y 31.00-32.99cm constituyeron los peces más frecuentemente explotados. Un aumento de la longitud total de la quebrada (media±SD; 16.19±3.73cm) para el hábitat marino (32.89±6.14cm) indicó un cambio ontogenético en el uso del hábitat. La aparición de una población juvenil predominante en Five Cowrie Creek por L. goreensis sugiere una estuario-dependencia y es indicativa de un hábitat juvenil temporal o un corredor migratorio. En conclusión, los datos del estudio actual y estudios previos demostraron que juveniles de L. goreensis presentan una dependencia a los estuarios y una flexibilidad en el uso de hábitat. Por lo tanto, esto subraya la importancia de preservar los ambientes estuarinos como hábitats esenciales de peces para evitar la sobrepesca. El estudio también concluye que la especie es vulnerable a la sobrepesca de reclutamiento en el medio marino, especialmente como consecuencia de la pesca de camarón. En consecuencia, se aboga por la prohibición de todas las actividades pesqueras durante los períodos de mayor puesta de huevos.

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This constitutes the first record of the Australian alien mytilid Xenostrobus securis in China. The introduction occurred prior to 2010 probably via shipping arriving at Yantian in Mirs Bay, China, close to Hong Kong. Point sources of infection could be Australia or Korea or Japan where it has similarly been introduced. Analysis of X. securis in Hong Kong shows that it tolerates a wide range of salinities from 5.4‰ to 28.7‰. Water temperatures in Hong Kong match those in its native range. In Hong Kong, X. securis co-occurs with the similarly introduced Mytilopsis sallei and a native bivalve community. The population structure of X. securis suggests a lifespan of >2 years with new generations produced by conspecifics. Such a life history strategy is also exhibited by M. sallei. Now established in China, northern Asia, the Mediterranean and, most recently, the Iberian Atlantic, the invasion of other locations by X. securis seems probable.

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Ladyfish (Elops sp) are a common and economically valuable coastal nearshore species found along coastal beaches, bays, and estuaries of the southeastern United States, and subtropical and tropical regions worldwide. Previously, ladyfish were a substantial bycatch in Florida's commercial fisheries, but changes in regulations significantly reduced commercial landings. Today, ladyfish are still taken in commercial fisheries in Florida, but many are also taken by recreational anglers. Life-history information and research interest in ladyfish is almost non-existent, especially information on age and growth. Thus, the overarching purpose of this study was to expand our understanding of ladyfish age and growth characteristics. The specific objectives were to describe, for the first time, age, growth, and recruitment patterns of juvenile ladyfish from the east coast of Florida (USA). In the Indian River Lagoon (IRL), annual monthly length-frequency distributions were confounded because a few small individuals recruited throughout the year; monthly length-frequency data generally demonstrated a cyclical pattern. The smallest were collected in September and the largest in May. Post-hoc analysis showed no significant difference in length between August and May, or among the other months. In Volusia County (VC), annual monthly length-frequency distribution demonstrated growth generally occurred from late-winter and spring to summer. The smallest ladyfish were collected in February and the largest in August. On average, the absolute growth rate in the IRL was 36.3 mm in 60 days or 0.605 mm day(-1). Cohort-specific daily growth rates, elevations, and coincidentals were similar among sampling years. Cohort-specific growth rates ranged from 1.807 in 1993 to 1.811 mm day(-1) in 1994. Overall, growth was best (i.e., goodness of fit) described by exponential regression. On average, the absolute growth rate in VC was 28 mm in 150 days or 0.1866 mm day(-1). Cohort-specific daily growth rates were significantly different among sampling years; however, the elevations and coincidentals were similar. Cohort-specific growth rates ranged from 1.741 in 1994 to 1.933 mm day(-1) in 1993. Mean ladyfish growth was best described by linear regression; however, natural growth was explained better by exponential regression. In the IRL, the corrected exponential growth equation yielded a size-at-age 1 of 156.0 mm SL, which corresponded to an estimated growth rate of 0.4356 mm day(-1). In VC, the corrected exponential growth equation yielded a size-at-age 1 of 80 mm SL corresponding to an estimated growth rate of 0.2361 mm day(-1).

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The population structure and reproductive condition of the Sinaloa cichlid Cichlasoma beani from samples obtained from June 2000 to July 2001 were determined. Samples in the first week each month from the largest trader of tilapia in the Aguamilpa Reservoir in Mexico and were caught in gillnets (9.6 and 11.4 cm stretch-mesh size). Of 596 specimens, there were 427 males and 169 females; monthly sex ratio, frequency of lengths by the multinomial distribution, timing of reproduction, condition index, and size at first maturity was determined. Differences in the sex ratio and monthly totals were significant, favoring males, except for September 2000 and March 2001. From one (August 2000) to three modal groups (July 2000 and June 2001) were identified by size. There were no significant differences in standard length weight relationships by sex, which indicated that a shared model for both genders is appropriate, and isometric growth was detected. Based on the proportion of mature and partially matures fish, the main reproductive period was April through June; size at first maturity was 18.9 cm. Water temperature was not significantly related to the percentage of mature and partially matures Sinaloa cichlids or spawning. These findings provide information for regulating the Cichlasoma beani fishery in this region such minimum legal size and non-fishing period.

Se determinó la estructura poblacional y condición reproductiva del cíclido de Sinaloa Cichlasoma beani desde junio de 2000 a julio de 2001. Las muestras se obtuvieron de la captura comercial de tilapia en el embalse de Aguamilpa, México durante la primera semana de cada mes. Los especímenes se capturaron con redes de enmalle (9,6 y 11,4 cm de tamaño de malla). De los 596 organismos recolectados, 427 fueron machos y 169 hembras. Se determinó la proporción de sexos mensual, grupos modales de tallas a través de una distribución multinomial, época reproductiva, índice de condición y talla de primera madurez. Se encontraron diferencias significativas en la proporción de sexos total y mensual favoreciendo a los machos, excepto en septiembre de 2000 y marzo de 2001. Se identificaron desde uno (agosto de 2000) hasta tres grupos modales de tallas (julio de 2000 y junio de 2001). No se encontraron diferencias significativas en la relación longitud patrón - peso total por sexo, lo que sugiere que el uso de un solo modelo para ambos sexos es adecuado, presentando crecimiento de tipo isométrico. Con base en la proporción de organismos parcialmente maduros y maduros, el pico principal de reproducción fue desde abril hasta junio; la talla de primera madurez fue de 18,9 cm. No se encontró una correlación significativa entre la temperatura del agua y el porcentaje de individuos parcialmente maduros, maduros o desovados. La información generada es útil para la regulación de la pesca de Cichlasoma beani en esta región, sugiriendo una talla mínima legal de captura y un periodo de veda adecuado para la especie.

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RESUMEN

The Pacific jack Caranx caninus is a common species fished by artisanal fishermen off the coast of Colima, México. During 2002, monthly samples of morphometric data and otoliths were taken to determine age and growth. Seven age groups were identified. The highest growth, 14.4 cm, takes place during the first year of life. During the second year, C caninus grows 11.76 cm; the third year 9.61 cm; the fourth 7.85 cm; the fifth 6.41 cm and sixth year 5.24 cm. The constants of von Bertalanffy's growth equation were: L(infinity) = 83.26 cm, W(infinity) = 18.138 g, K = 0.202, t(0) = -0.283 and A(0.95) = 15 years. Growth curves of other species of the same genus were calculated in order to compare them with the one obtained in the present work. The gonadosomatic index presented higher values during November and May. The periods of more intensive feeding are from August to February.

El jurel Caranx caninus es una especie común que se captura en la pesca artesanal frente a las costas de Colima, México. Mensualmente, durante 2002, se tomaron datos morfométricos y muestras de otolitos para determinar la edad y el crecimiento. Se encontraron siete grupos de edad; durante el primer año de vida se da el mayor crecimiento, hasta 14.4 cm. Durante el segundo año, C. caninus crece 11.76 cm; el tercero 9.61 cm; el cuarto 7.85 cm; el quinto 6.41 cm y el último año crece 5.24 cm. Las constantes de la ecuación de crecimiento de von Bertalanffy fueron: L∞ = 83.26 cm, W∞ = 18.138 g, K = 0.202, to = -0.283 y la longevidad A0.95 = 15 años. Las curvas de crecimiento de otras especies del mismo género se compararon con las obtenidas en el presente trabajo. El índice gonadosomático presentó valores más altos durante noviembre y mayo. Los periodos de tiempo de alimentación más intensa son de agosto a febrero.

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