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ABSTRACT The recognition of oocytes, in their maturational stages, allow estimate the ovarian development and the type of spawning of a species. Although, distinguishing oocytes on histological images requires a visual and subjective interpretation by the specialist. With the development of deep learning techniques, automatic object detection has become an important mechanism for this task. However, studies that use deep learning techniques have not been widely explored for the analysis of fish oocyte samples so far. In this paper, we propose the use of YOLO, a family of convolutional neural networks, for oocyte morphology detection of Centropomus undecimalis fish. The research uses an image database with 5,680 oocytes with different maturation stadiums (PV - pre-vitellogenesis, VI - early vitellogenesis and VF - late vitellogenesis), in histological images, divided into training, testing and validation, and detection performed by YOLOv3, YOLOv4, and YOLOv5 architectures. The results obtained were promising, highlighting that the YOLOv5l model, in the detection of oocytes of the VF class, reached the best values in the metrics precision, recall, mAP@.5 and mAP@.95 with 85.4%, 95.3%, 95.7%, and 75.9%, respectively. When considering all classes, YOLOv5l was the model that obtained the best results in the analyzed metrics.

Development of Florida's marine Fisheries-Independent Monitoring (FIM) program began in 1985, and it initiated long-term monitoring in Tampa Bay in 1989 with the purpose of providing timely fishery-independent data and analyses to fishery managers for the conservation and protection of the species that support Florida's fisheries. Over time, the program expanded sampling in other Florida estuaries. Data from this monitoring program are integral to the assessment and management of numerous state and federally managed fishes, so long-term consistency is of paramount importance, but sampling design modifications have been necessary over time. This review presents three case studies in which the estuarine component of the FIM program was changed to address emerging data needs in management of Florida's fishery resources, while maintaining standardization and consistency with long-term surveys statewide. In the first case study, survey changes increased the amount of data on juvenile common snook, Centropomus undecimalis, on the Gulf of Mexico and Atlantic coasts and improved indices of abundance, survival estimates, and age-length keys for state management purposes. In the second case study, the FIM program improved estimates of abundance of juvenile reef fishes by initiating a complementary survey that expanded FIM sampling to new regions of the Florida Gulf coast and targeted a unique habitat (polyhaline seagrass beds along estuarine shoal habitats) not previously sampled in the standard longterm survey. In the third case study, the FIM program addressed a data limitation for regional management of spotted seatrout, Cynoscion nebulosus, by initiating seasonal sampling in western Florida. In each case study, the standard long-term survey design was modified to include sampling of new and unique areas and habitats, providing valuable data on estuarine fish assemblages that support analyses at the broader, ecosystem level. Survey amendments were designed to maintain standardization and consistency, all with limited additional funding. The success of these survey modifications was the result of several key factors: mission-focused programmatic goals, geographically dispersed laboratories, standardized protocols, ongoing critical analysis of the data, grant award success, and high-level data management. Although each case study originated with a survey expansion, all were followed by survey reductions or streamlining, so expansion and reduction scenarios are presented in this review. Regardless of these modifications, the mission of the FIM program remains the same: to provide timely data and analysis for the use of fishery managers, including state and federal partners. [ABSTRACT FROM AUTHOR]

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Development of Florida’s marine Fisheries-Independent Monitoring (FIM) program began in 1985, and it initiated long-term monitoring in Tampa Bay in 1989 with the purpose of providing timely fishery-independent data and analyses to fishery managers for the conservation and protection of the species that support Florida’s fisheries. Over time, the program expanded sampling in other Florida estuaries. Data from this monitoring program are integral to the assessment and management of numerous state and federally managed fishes, so long-term consistency is of paramount importance, but sampling design modifications have been necessary over time. This review presents three case studies in which the estuarine component of the FIM program was changed to address emerging data needs in management of Florida’s fishery resources, while maintaining standardization and consistency with long-term surveys statewide. In the first case study, survey changes increased the amount of data on juvenile common snook, Centropomus undecimalis, on the Gulf of Mexico and Atlantic coasts and improved indices of abundance, survival estimates, and age-length keys for state management purposes. In the second case study, the FIM program improved estimates of abundance of juvenile reef fishes by initiating a complementary survey that expanded FIM sampling to new regions of the Florida Gulf coast and targeted a unique habitat (polyhaline seagrass beds along estuarine shoal habitats) not previously sampled in the standard long-term survey. In the third case study, the FIM program addressed a data limitation for regional management of spotted seatrout, Cynoscion nebulosus, by initiating seasonal sampling in western Florida. In each case study, the standard long-term survey design was modified to include sampling of new and unique areas and habitats, providing valuable data on estuarine fish assemblages that support analyses at the broader, ecosystem level. Survey amendments were designed to maintain standardization and consistency, all with limited additional funding. The success of these survey modifications was the result of several key factors: mission-focused programmatic goals, geographically dispersed laboratories, standardized protocols, ongoing critical analysis of the data, grant award success, and high-level data management. Although each case study originated with a survey expansion, all were followed by survey reductions or streamlining, so expansion and reduction scenarios are presented in this review. Regardless of these modifications, the mission of the FIM program remains the same: to provide timely data and analysis for the use of fishery managers, including state and federal partners.

Centropomus undecimalis (common snook) and Centropomus parallelus (fat snook) have a wide distribution from southern Florida to southern Brazil. Due to their value as a food source, these species have been heavily exploited through predatory fishing, posing a conservation challenge. To assess their genetic diversity and population structure, we used microsatellite markers. Our findings revealed genetic differences among populations of the same species, highlighting the need for targeted conservation efforts. The microsatellite markers proved effective in assessing genetic variability, providing valuable insights for management and conservation. The parameters Ho (observed heterozygosity) and He (expected heterozygosity) were reliable indicators of genetic diversity, and specific loci showed varying allele numbers across populations. Our study contributes to understanding population genetics in these snook species and supports their conservation. Despite not being classified as endangered, genetic differences among populations emphasize the importance of considering population-level characteristics in conservation strategies. This research lays the foundation for future studies and actions aimed at preserving these valuable fish species. In summary, our study demonstrates the significance of microsatellite markers in assessing genetic variability and population structure in common snook and fat snook, informing conservation efforts for these species. [ABSTRACT FROM AUTHOR]

Abstract Background Spawning migrations are a widespread phenomenon among fishes, often occurring in response to environmental conditions prompting movement into reproductive habitats (migratory cues). However, for many species, individual fish may choose not to migrate, and research suggests that conditions preceding the spawning season (migratory primers) may influence this decision. Few studies have provided empirical descriptions of these prior conditions, partly due to a lack of long-term data allowing for robust multi-year comparisons. To investigate how primers and cues interact to shape the spawning migrations of coastal fishes, we use acoustic telemetry data from Common Snook (Centropomus undecimalis) in Everglades National Park, Florida, USA. A contingent of Snook migrate between rivers and coastal spawning sites, varying annually in both the proportion of the population that migrates and the timing of migration within the spawning season. However, the specific environmental factors that serve as migratory primers and cues remain unknown. Methods We used eight years of acoustic telemetry data (2012–2019) from 173 tagged Common Snook to investigate how primers and cues influence migratory patterns at different temporal scales. We hypothesize that (1) interannual differences in hydrologic conditions preceding the spawning season contribute to the number of individuals migrating each year, and (2) specific environmental cues trigger the timing of migrations during the spawning season. We used GLMMs to model both the annual and seasonal migratory response in relation to flow characteristics (water level, rate of change in water level), other hydrologic/abiotic conditions (temperature, salinity), fish size, and phenological cues independent of riverine conditions (photoperiod, lunar cycle). Results We found that the extent of minimum marsh water level prior to migration and fish size influence the proportion of Snook migrating each year, and that high river water level and daily rates of change serve as primary cues triggering migration timing. Conclusion Our findings illustrate how spawning migrations are shaped by environmental factors acting at different temporal scales and emphasize the importance of long-term movement data in understanding these patterns. Research providing mechanistic descriptions of conditions that promote migration and reproduction can help inform management decisions aimed at conserving ecologically and economically important species.

Background: Spawning migrations are a widespread phenomenon among fishes, often occurring in response to environmental conditions prompting movement into reproductive habitats (migratory cues). However, for many species, individual fish may choose not to migrate, and research suggests that conditions preceding the spawning season (migratory primers) may influence this decision. Few studies have provided empirical descriptions of these prior conditions, partly due to a lack of long-term data allowing for robust multi-year comparisons. To investigate how primers and cues interact to shape the spawning migrations of coastal fishes, we use acoustic telemetry data from Common Snook (Centropomus undecimalis) in Everglades National Park, Florida, USA. A contingent of Snook migrate between rivers and coastal spawning sites, varying annually in both the proportion of the population that migrates and the timing of migration within the spawning season. However, the specific environmental factors that serve as migratory primers and cues remain unknown. Methods: We used eight years of acoustic telemetry data (2012–2019) from 173 tagged Common Snook to investigate how primers and cues influence migratory patterns at different temporal scales. We hypothesize that (1) interannual differences in hydrologic conditions preceding the spawning season contribute to the number of individuals migrating each year, and (2) specific environmental cues trigger the timing of migrations during the spawning season. We used GLMMs to model both the annual and seasonal migratory response in relation to flow characteristics (water level, rate of change in water level), other hydrologic/abiotic conditions (temperature, salinity), fish size, and phenological cues independent of riverine conditions (photoperiod, lunar cycle). Results: We found that the extent of minimum marsh water level prior to migration and fish size influence the proportion of Snook migrating each year, and that high river water level and daily rates of change serve as primary cues triggering migration timing. Conclusion: Our findings illustrate how spawning migrations are shaped by environmental factors acting at different temporal scales and emphasize the importance of long-term movement data in understanding these patterns. Research providing mechanistic descriptions of conditions that promote migration and reproduction can help inform management decisions aimed at conserving ecologically and economically important species. [ABSTRACT FROM AUTHOR]

Located on Florida's Nature Coast, the Weeki Wachee River, Chassahowitzka River, Homosassa River, and Kings Bay/Crystal River Systems serve as winter thermal refugia for fish and wildlife and face complex threats, including climate change. Rising temperatures have resulted in species distribution shifts in the Gulf of Mexico, including the northward range expansion of Common Snook (Centropomus undecimalis). We assessed whether Common Snook are utilizing these springs systems and if their abundance and distribution varied temporally, seasonally, and spatially. From Winter 2013 through Winter 2019, 3,690 Common Snook were captured; only 21 were captured in the Weeki Wachee River System, while 1,796 fish were captured in the Kings Bay/Crystal River System. The Kings Bay/Crystal River System Common Snook catch increased through time. The average number of fish caught during the winter was higher than the average summer catch for the Homosassa River System. Temporal and spatial patterns in the juvenile and adult Common Snook catch were found. Our results demonstrate the establishment of year-round populations of Common Snook in the Nature Coast springs systems and their importance as winter thermal refugia. The continued availability of winter thermal refugia is critical to the sustainability of Common Snook populations along the Nature Coast. [ABSTRACT FROM AUTHOR]

Carnivorous common snook (Centropomus undecimalis) has potential for aquaculture, but its protein requirement in diet is 500 g kg−1 and the energetic role of lipids in this species has not been explored. Thus, this study investigated the ability of juvenile common snook (8.7 ± 1.2 g) to use dietary lipids as an energy source. The fish were fed four practical diets with two protein levels (400 and 500 g kg−1) associated with two lipid levels (60 and 120 g kg−1) for 12 weeks. Growth performance significantly improved with increasing dietary lipid levels, but no significant difference was observed at the protein level. Fish fed the 400:60 (protein: lipid level) diet exhibited significantly higher feed conversion ratios than those fed 400:120, 500:60 and 500:120 diets, but fish fed the 400:120 diet had significantly higher protein efficiency ratios. Juvenile common snook showed the ability to modulate digestive protease and lipase secretion when dietary protein or lipid levels were modified. The activity of alanine aminotransferase decreased as the dietary lipid level increased (p <.05), while fructose‐1 and 6‐bisphosphatase activities were not significantly affected by dietary protein or lipid levels. Glucose‐6‐phosphate dehydrogenase, 6‐phosphogluconate dehydrogenase and pyruvate kinase activities increased as dietary protein and lipid levels increased (p <.05). The results of this study indicate that an increase in dietary lipid level has a protein‐sparing effect and that the diet containing 400 g kg−1 protein with 120 g kg−1 lipid is suitable for growth and effective protein utilization in common snook. [ABSTRACT FROM AUTHOR]

ABSTRACT: Essential oils of plants whose main compound is citral showed beneficial effects when added to fish feed. The objective of the present study was to evaluate the dietary effect of the addition of citral on zootechnical parameters and digestive enzyme activities of Centropomus undecimalis. Juveniles were fed for 45 days with diets containing different amounts of citral (0.0 - control, 0.5, 1.0, and 2.0 mL per kg of diet). The water quality parameters were kept stable during the experiment and no mortality was observed. At the end of the experimental period, the treatment 0.5 mL citral per kg of diet had the lowest weight gain and specific growth rate, and the highest feed conversion, while the same parameters did not differ between the other treatments. Pepsin activity was higher in the stomach of fish fed with 0.5 mL citral per kg of diet and amylase activity was higher in the intestine of fish fed with 0.5 and 2.0 mL citral per kg of diet compared to the control group. Intestinal lipase activity was higher in all groups that were fed with citral compared to the control group. Chymotrypsin and trypsin activities showed no difference between groups. Consequently, dietary addition of citral at any of the levels tested is not recommended for common snook.

The assumption for hermaphroditic fish species that mature individuals of the terminal sex arise directly from mature individuals of the primary sex has led to the use of sex ratios as a proxy for age at maturity (A50). The timing of transition and deficient energy reserves, however, can result in a delay between transition and spawning. To test the assumption of female maturity and investigate the relationship between maturation and energy reserves, common snook, Centropomus undecimalis, a protandrous hermaphrodite, were collected from rivers, estuaries, inlets and offshore habitats on the east coast of Florida during 2010–2015. Immature females were observed every month, with lowest proportions during the peak spawning months of July and August. When calculated based on sex ratio, A50 (8.1 years) overestimated the age at which 50% of the female population was, in fact, mature (4.1–4.9 years). Best‐fit models indicate that mesenteric fat index (IF) and hepato‐somatic index (IH) were significantly affected by gonad phase, month and size and weakly by habitat. In post hoc analysis, immature female IF did not differ significantly from developing and regenerating females, but immature female IH was significantly lower than that for all mature phases except animals in the regressing phase. Although immature females may have sufficient energy in terms of fat, it appears that energy is not allocated to reproductive processes, as evidenced by lower IH. Nonetheless, approximately 95% of females were spawning‐capable during peak spawning months, suggesting that the energy threshold at which immature females reach maturity is met by most females each spawning cycle. [ABSTRACT FROM AUTHOR]

Extreme climate events such as hurricanes can influence the movement and distribution of fish and other aquatic vertebrates. However, our understanding of the scale of movement responses and how they vary across taxa and ecosystems remains incomplete. In this study, we used acoustic telemetry data to investigate the movement patterns of common snook (Centropomus undecimalis) in the Florida Coastal Everglades during Hurricane Irma, which made landfall on the southwest Florida coast as a Category 3 storm on 10 September 2017 after passing in close proximity to our study site. We hypothesized that the hurricane resulted in shifts in distribution and that these movements may have been driven by environmental cues stemming from changes in barometric pressure associated with hurricane conditions, fluctuations in water levels (stage) characterizing altered riverine conditions, or a combination of both hurricane and riverine drivers. The data revealed large-scale movements of common snook in the time period surrounding hurricane passage, with 73% of fish detected moving from the upper river into downriver habitats, and some individuals potentially exiting the river. Furthermore, regression model selection indicated that these movements were correlated to both hurricane and riverine conditions, showing increased common snook movement at higher river stage and lower barometric pressure, and stage explaining a larger proportion of model deviance. Animal movement has widespread and diverse ecological implications, and by better understanding the factors that drive movement, we may anticipate how future extreme climate events could affect fish populations in impact-prone regions. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this work was to evaluate the growth performance of common snook (Centropomus undecimalis) subjected to different feeding rates and frequencies using automatic feeders. Two experiments of 60 days each were carried out. In the first one, 20 fishes per tank were distributed in three feeding rates of: 5, 10, and 15% body weight per day. In the second experiment, 20 fishes per tank were distributed in nine tanks, in three feeding frequency: once a day, three times a day, and six times a day. Water parameters were maintained at the recommended level for the species. Final weight, body weight gain, specific growth rate, and feed conversion rate did not differ significantly between the 10 and 15% feeding rates. However, both rates differed from the 5% one. The feeding frequency of six times a day resulted in better values for final weight, final biomass, body weight gain, and specific growth rate. Therefore, common snook fingerlings should be fed at the feeding rate of 10% body weight per day, six times a day, in order to achieve the best growth performance.

The common snook is one of the most abundant and economically important species in the Usumacinta basin in the Gulf of Mexico, which has led to overfishing, threatening their populations. The main goal of the present study was to assess the genetic diversity and structure of the common snook along the Usumacinta River in order to understand the population dynamics and conservation status of the species. We characterized two mitochondrial markers (mtCox1 and mtCytb) and 11 microsatellites in the Usumacinta basin, which was divided into three zones: rainforest, floodplain and river delta. The mitochondrial data showed very low diversity, showing some haplotypic diversity differences between the rainforest and delta zones. In contrast, we consistently recovered two genetic clusters in the Usumacinta River basin with the nuclear data in both the DAPC and STRUCTURE analyses. These results were consistent with the AMOVA analyses, which showed significant differences among the genetic clusters previously recovered by DAPC and STRUCTURE. In terms of diversity distribution, the floodplain zone corresponded to the most diverse zone according to the mitochondrial and nuclear data, suggesting that this is a transition zone in the basin. Our results support the relevance of the molecular characterization and monitoring of the fishery resources at the Usumacinta River to better understand their connectivity, which could help in their conservation and management.

The skin-associated microbiota of fish competes against pathogens for space and nutrients, preventing colonization by harmful bacteria encountered during environmental transitions such as those faced during stock enhancement. Thus, alterations in bacterial community structure during release of cultured fish have important implications for health of these individuals. This study investigated microbiota structure during acclimation of juvenile hatchery-reared common snook Centropomus undecimalis to the wild by comparing skin-associated microflora among snook in captivity, after 48 h of acclimation at release sites, and from the wild. After two days of acclimation, the microbiota of hatchery-reared snook mirrored that observed on wild snook. Relative abundances of potential pathogens were higher in captive fish, whereas acclimated and wild fish harbored bacterial taxa influenced by geographical factors and water quality at release sites. Predicted microbiota function of acclimated and wild fish showed higher production of protective amino acids and antimicrobials, identifying a mechanism for microbial supplementation of the immune defense of these fish. The two-day transition to wild-type microbiota suggests a temporal scale of hours associated with bacterial succession indicating that the microbiota, whose structure is vital to fish health, aids in acclimation of fish to new environments during stock enhancement efforts. [ABSTRACT FROM AUTHOR]

Resumo: O objetivo deste trabalho foi avaliar o efeito da privação alimentar e a ocorrência de crescimento compensatório sobre o desempenho produtivo de formas jovens do robalo-flecha (Centropomus undecimalis). O experimento teve duração de 60 dias, em que os peixes - 35 indivíduos por tanque - foram divididos nos três seguintes grupos de tratamentos: com alimentação todos os dias (controle); com alimentação cinco dias por semana, seguidos de dois dias de jejum; e com alimentação quatro dias por semana, seguidos de três dias de jejum. Os tratamentos de privação alimentar proporcionaram indicadores de desempenho significativamente inferiores aos do controle. Formas jovens da espécie não devem ser submetidas a períodos de privação alimentar, pelos prejuízos que esta prática acarreta ao desempenho produtivo.

The objective of this work was to evaluate the addition of Bacillus subtilis probiotic to the feed of common snook (Centropomus undecimalis) fingerlings, in alternate and continuous regimens. Six hundred and sixty fish, with average length of 5.90±0.88 cm and weight of 1.92±0.28 g, were stocked in 12 cages of 1.0 m3, with 55 fish each. The experimental design was completely randomized, with three treatments and four replicates. The treatments consisted of diet with the addition of probiotic, provided in alternate regimen for 7 days and in continuous regimen; besides a control without probiotic in the feed. Zootechnical performance, body composition, immune response, and blood parameters were evaluated. No significant differences were observed in zootechnical performance indexes and in body composition of fish treated with probiotic, when compared to the control. Fish from the alternate regimen showed an increment in respiratory burst and a lower total erythrocyte count than fish from the continuous regimen and the control. Fish from the continuous regimen did not differ from those of the control. The addition of Bacillus subtilis does not increase growth rates of common snook fingerlings; however, it has an immunostimulant action when supplied in alternate regimen.

Parasitism in fish can occur due to an imbalance in the environment-host-parasite relationship, usually associated with poor environmental quality. The present study aimed to determine the frequency of parasitism and histological alterations in the gills of Centropomus undecimalis from the Jansen Lagoon Ecological Park in São Luís, Maranhão, Brazil. Thirty-three specimens of C. undecimalis were collected. The first right gill arch was removed from each animal and fixed in 10% formalin for 24 h. These were then decalcified in 10% nitric acid, dehydrated in increasing concentrations of alcohol, clarified in xylene and impregnated with and embedded in paraffin. Five-μm thick sections were stained with hematoxylin and eosin for histologic description and to determine parasite frequency. The gill lesions of each fish were semiquantitatively evaluated by calculating the histological alteration index (HAI). Structural alterations in the gills, such as epithelial hyperplasia and mucus, were associated with parasites in 48.4% of the fish. Three families of parasites from the Monogenean and Myxosporean groups were identified. The HAI average was 53.3, demonstrating that individuals collected from C. undecimalis had severe tissue modifications. Therefore, parasitism caused structural damages in the gill tissues of sampled fish, damages that can impair the organ's physiology, and harm the fish health. [ABSTRACT FROM AUTHOR]

El robalo común Centropomus undecimalis habita en áreas ribereñas y marinas del sur del Golfo de México donde es sujeto a explotación intensiva. Aunque la identificación de las poblaciones de peces representa una valiosa herramienta para el manejo de las poblaciones silvestres, no hay información disponible para identificar genéticamente las poblaciones de peces de esta especie en la región. El objetivo de este estudio fue determinar la relación genética entre C. undecimalis capturado en ambiente marino y dulceacuícola del Golfo de México y río San Pedro. Muestras de tejido muscular de 79 individuos fueron obtenidas en áreas separadas por más de 300km. El genotipo de cada individuo fue determinado usando siete pares de cebadores microsatélites. Cinco cebadores amplificaron eficientemente presentando entre seis y 28 alelos por locus. Altos niveles de heterocigosidad se observaron en las muestras de ambos ambientes. Se observó desviación del equilibrio HW debido a exceso de heterocigotos. Los valores de diferenciación genética indican ausencia de estructuración poblacional F ST (0.0075) y R ST (0.016, p=0.051) y similitud en las frecuencias alélicas definidas por el índice de Nei (0.805). Los datos mostraron elevado flujo genético debido al número de migrantes (Nm=18.7). Estos resultados sugieren que los individuos en estos ambientes provienen de la misma población genética. La información obtenida en este estudio, por lo tanto contribuirá con elementos que pueden ser considerados en el desarrollo de programas de manejo y protección de las poblaciones de peces silvestres.

Com o objetivo de analisar a intensidade das alterações histológicas em brânquias de Centropomus undecimalis para avaliar a qualidade da água do Parque Ecológico Laguna da Jansen, em São Luís, Estado do Maranhão, coletaram-se exemplares de peixes no período chuvoso de 2012 e amostras de água nos períodos seco de 2011 e chuvoso de 2012 para análises físico-química e bacteriológica. Os resultados mostraram que a maioria dos parâmetros físico-químicos e bacteriológicos estava de acordo com os valores estabelecidos pela Resolução do CONAMA nº 357 de 2005. As alterações histológicas observadas foram: elevação do epitélio lamelar; proliferação excessiva de células dos epitélios filamentar e lamelar causando fusão total ou parcial das lamelas; alteração da estrutura das lamelas; hiperplasia das células mucosas; ruptura do epitélio lamelar; espessamento descontrolado do tecido proliferativo filamentar e lamelar e aneurismas de vários tamanhos. Também foi observada a presença de parasito em alguns exemplares. O Índice de Alteração Histológica (IAH) por indivíduo variou de 2 a 114. O valor médio do IAH obtido foi de 40,3, demonstrando que as brânquias dos indivíduos amostrados da espécie C. undecimalis apresentaram alterações de moderadas para severas no tecido. As alterações histológicas encontradas indicam que esses indivíduos desenvolveram mecanismos de defesa contra a ação de estressores presentes na água da laguna e a um provável desequilíbrio parasito-hospedeiro-ambiente associado à baixa qualidade do ambiente.

The adaptation of common snook Centropomus undecimalis to low salinities and freshwater has being widely studied, but the definition of the best water hardness levels may facilitate the adaptation and growth of this species in freshwater. Consequently, the aim of this study was to evaluate survival, growth and metabolic parameters (blood glucose and osmolality and lactate in plasma and tissues) of common snooks raised in freshwater with different water hardness levels. In an acute experiment, juveniles were transferred from seawater 35 ppt to seawater 35 ppt (control) and freshwater at 20, 100, 250, 500 or 1000 mg CaCO 3 L − 1 . Mortality after 96 h was 100, 79.17, 58.33, 4,17 and 50%, respectively. In another experiment juveniles (initial weight 10.9 ± 1.5 g) were maintained for 60 days in water hardness of 100, 500 or 1000 mg CaCO 3 L − 1 or seawater (control). No mortality was observed in this experiment. The best weight gain, specific growth rate and feed intake in freshwater (values not significantly different from seawater) was observed in common snooks kept at 100 mg CaCO 3 L − 1 . Blood and hepatic glucose did not differ significantly between treatments. Muscle glucose levels were significantly lower in fish kept at 100 and 1000 mg CaCO 3 L − 1 than the other treatments. However, lactate levels were higher in the muscle of common snooks kept at 100 to 500 CaCO 3 mg L − 1 and lactate in plasma was higher in those maintained at 1000 mg CaCO 3 L − 1 . Plasma osmolality was not affected significantly by treatments. In conclusion, 100 mg CaCO 3 L − 1 is the best water hardness to raise common snooks in freshwater. [ABSTRACT FROM AUTHOR]

The article discusses a study focusing on high mortality of the microbiota of common snook Centropomus undecimalis larvae. Topics discussed include the closed recirculating aquaculture systems (RAS), the effects of commercial mix of Bacillus on survival, growth and microbiota of larval common snook, and the use of DNA extractions in the study.

The objective of this work was to evaluate the efficacy of eugenol as an anesthetic for juvenile common snook, and to determine the minimum effective concentration for use in handling procedures. In the first trial, juvenile common snook were subjected to immersion baths at 25, 50, 75, 100, 125, and 150 mg L-1 eugenol concentrations, after which induction and recovery times were evaluated. In the second experiment, the lethal exposure time (LT50) at 75 mg L-1 was estimated. Minimum effective eugenol concentration was 50 mg L-1, andthe stage of deep anesthesia and recovery were, respectively, reached at 126.3 and 208.8 s. At 75 mg L-1, LT50 was 1,314 s, and induction time and recovery were also satisfactory; however, fish cannot tolerate over 229 s exposure.

Common snook Centropomus unidecimalis is an important commercial and fishery species in Southern Mexico, however the high exploitation rates have resulted in a strong reduction of its abundances. Since, the information about its population structure is scarce, the objective of the present research was to determine and compare the age structure in four important fishery sites. For this, age and growth of common snook were determined from specimens collected monthly, from July 2006 to March 2008, from two coastal (Barra Bosque and Barra San Pedro) and two riverine (San Pedro and Tres Brazos) commercial fishery sites in Tabasco, Mexico. Age was determined using sectioned saggitae otoliths and data analyzed by von Bertalanffy and Levenberg-Marquardt among others. Estimated ages ranged from 2 to 17 years. Monthly patterns of marginal increment formation and the percentage of otoliths with opaque rings on the outer edge demonstrated that a single annulus was formed each year. The von Bertalanffy parameters were calculated for males and females using linear adjustment and the non-linear method of Levenberg-Marquardt. The von Bertalanffy growth equations were FLt=109.21(1-e-0.21(t+0.57)) for Barra Bosque, FLt=94.56(1-e-0.27(t+0.48)) for Barra San Pedro, FLt=97.15(1-e-0.17(t+1.32)) for San Pedro and FLt=83.77(1-e-0.26(t+0.49)) for Tres Brazos. According to (Hotelling’s T², p

Current essay describes three new Monogenean species, namely, Cosmetocleithrum striatuli sp. nov., Jainus leporini sp. nov. and Rhabdosynochus guanduensis sp. nov., parasites on the gills of Trachelyopterus striatulus (Steindachner, 1877), Leporinus copelandii Steindachner, 1875 and Centropomus undecimalis (Bloch, 1792), respectively. Fish were collected from the Guandu river, State of Rio de Janeiro, Brazil between August 2005 and November 2008. Cosmetocleithrum striatuli sp. nov. differs from all other congeneric species by the shape of an accessory piece (more robust and resembling a crustacean claw or chela) and by the shape of its ventral and dorsal bars (not V-shaped and with expanded lateral ends directed to the rear). Jainus leporini sp. nov. differs from all other Jainus species by the male copulation organ (MCO), with a 2-ring coil, by the absence of medial projection on ventral bar and by a plate-like sclerotized structure associated to the vagina. Rhabdosynochus guanduensis sp. nov. differs from all other congeneric species by the morphology of the copulation complex and by a shell-shaped vagina.Três novas espécies, Cosmetocleithrum striatuli sp. nov., Jainus leporini sp. nov. e Rhabdosynochus guanduensis sp. nov., parasitando as brânquias de Trachelyopterus striatulus (Steindachner, 1877), Leporinus copelandii Steindachner, 1875 e Centropomus undecimalis (Bloch, 1792), respectivamente, são descritas no presente trabalho. Os peixes foram coletados do rio Guandu, Estado do Rio de Janeiro, Brasil, no período de agosto de 2005 a novembro de 2008. Cosmetocleithrum striatuli sp. nov. difere de todas as outras espécies congenéricas pelo formato da pesca acessória (muito robusta e semelhante a uma quela de crustáceo) e pelo formato das barras ventral e dorsal (sem o formato de V e com as extremidades laterais expandidas e direcionadas posteriormente). Jainus leporini sp. nov. difere de todas as outras espécies do gênero pelo órgão copulatório masculino (OCM) ter duas voltas de diâmetro do anel, pela ausência de projeção medial na barra ventral e por possuir uma vagina associada a uma estrutura esclerotizada em forma de placa. Rhabdosynochus guanduensis sp. nov. difere de todas as outras espécies congenéricas pela morfologia do complexo copulatório e pela vagina em forma de concha.

El robalo blanco Centropomus undecimalis, vive en hábitats marinos, salobres y dulceacuícolas en el océano Atlántico occidental, incluyendo el golfo de México. La especie, es económicamente importante en varias localidades, no obstante los estudios sobre su biología y genética son hasta el momento pocos. El presente estudio tiene como propósito, la caracterización citogenética de especímenes recolectados en el municipio de Paraíso, Tabasco, México. Cinco hembras y ocho machos fueron procesados por técnicas citológicas convencionales para la obtención de preparaciones cromosómicas de buena calidad para elaborar el cariotipo. Los resultados del análisis del tejido del riñón, mostraron que 85.1% de 288 mitosis tienen 2n=48 cromosomas y 52.8% de 104 meiosis exhiben el número haploide de 1n=24. El cariotipo diploide mostro 48 cromosomas monorrámeos de tipo telocéntrico (T). No se observó heteromorfismo cromosómico entre hembras y machos. El cariotipo diploide fue similar a los observados en la mayoría de peces marinos.

In Southeastern Mexico, Centropomus undecimalis is an important fish species of sport and commercial fisheries for coastal and riverine communities. Fisheries along rivers and coasts depend on migratory habits of this species, and these movements are probably related to reproduction. In spite of its economic importance, few studies have been conducted focusing on its reproductive biology, and this research aims to analyze these habits. Samples (fork length, somatic and gonads weight, and macroscopic maturity stages) were obtained from organisms collected by fishermen from the largest fishing cooperatives along the coastal and riverine areas of Tabasco, from July 2006 to March 2008. Fish size ranged from 34 to 112cm fork length, with an average age of 6.42 years for males and 9.12 years for females. In riverine areas, fish sizes ranged from 30 to 85cm and the average age was 5.5 years for males and 6.6 years for females. Significant differences were recorded between lengths of males and females from the two areas (Kruskal-Wallis, p0.05). A curve for eviscerated weight was calculated for both sexes, for coastal fishes SW=0.0059(FL) 3.07, and the riverine ones SW=0.0086(FL) 2.98, with an isometric growth (b=3). The period of maximum reproduction was from July to August, with temperatures of 28 to 30°C. A significant correlation between the gonadosomatic index (GSI) and rainfall was recorded for samples of both males and females from coastal areas (r=0.63, r=0.70) whereas only one positive correlation was recorded for riverine females (r=0.57). The size at first maturity (L50) was estimated at 60cm and 80cm (FL), corresponding to 5.5 and 8.5 years of age, for males and females, respectively. An important proportion of mature females of eight years and older, suggests that these ages contribute significantly to the reproductive biomass. The results indicate that due to changes in the exploitation period, we recommend to protect populations of the common snook. Rev. Biol. Trop. 59 (2): 669-681. Epub 2011 June 01.

Culture of C. undecimalis shows great potential as this species tolerates handling and adapts easily to captivity. However, the difficulty in achieving spawning in captivity is a major obstacle for the development of commercial scale farming. Spawning of common snook was achieved using GnRH-a implants in single 100 and 200 µg doses per fish; control group specimens received no hormone and did not spawn. Both GnRH-a trial doses resulted in spawning with up to 100% fertilization rates per experimental unit, and a range of 60 – 76% per treatment. A 50 – 100% hatching rate was obtained and larvae were between 1.56 ± 0.08 and 1.98 ± 0.05 mm total length after yolk sac absorption.

Estuaries are subjected to continual environmental impacts from activities in the catchment areas. This research assessed the quality of two estuarine habitats located in Ilha do Maranhão, Brazil, through histological and genotoxic biomarkers in Centropomus undecimalis, comparing the data obtained to metal, physical, and chemical concentrations of water samples. The gill histological alterations were analyzed by the histological alteration index and genotoxic lesions in erythrocytes were detected by the Micronucleus Test. The analysis of metals revealed that all water samples contained at least two elements with concentrations higher than that allowed by the current Brazilian law. For gill histological analysis, snook of both areas assessed exhibited moderate lesions, indicating that the local fish are affected by environmental stress. Micronucleus analysis of snook showed that the Bacanga river basin is the most affected. In addition to assessing the health of commercial fish populations, the information about the biomarkers used for the species can serve to contribute to the preparation and/or application of health assessment models and implementation of environmental recovery policies for coastal aquatic environments. [ABSTRACT FROM AUTHOR]

For species that are closely managed, understanding population resilience to environmental and anthropogenic disturbances (i.e., recovery trajectories across broad spatial areas) can guide which suite of management actions are available to mitigate any impacts. During January 2010, an extreme cold event in south Florida caused widespread mortality of common snook, Centropomus undecimalis, a popular sport fish. Interpretation of trends using fishery-independent monitoring data in five south Florida estuaries showed that changes in catch rates of adult snook (>500 mm standard length) varied between no effects postevent to large effects and 4-yr recoveries. The reasons for the variation across estuaries are unknown, but are likely related to differences in estuary geomorphology and habitat availability (e.g., extent of deep rivers and canals) and differences in the proportions of behavior contingents (i.e., segments of the population that use divergent movement tactics) that place snook in different areas of the estuary during winter. Emerging awareness of the presence of behavior contingents, identification of overwintering sites, and improvements of abundance indices in remote nursery habitats should provide a better understanding of population resilience to disturbance events for snook. Given that changes in the frequency of short-lived, severe cold events are currently unknown, the findings and management actions described here for a tropical species living at the edge of its distribution should be useful to scientists forecasting the effects of climate change. [ABSTRACT FROM AUTHOR]

O objetivo deste trabalho foi analisar a influência da densidade de estocagem no crescimento, conversão alimentar e sobrevivência de juvenis de robalo-flecha (Centropomus undecimalis). Os peixes foram coletados em ambiente natural e treinados a aceitar dietas artificiais. Os indivíduos, com comprimento total de 13±0,4 cm e peso de 23±0,3 g foram estocados em tanques circulares de fibra de vidro de 5 m³, com água do mar e aeração contínua, nas densidades de 3, 6 e 9 peixes/m³, por 180 dias. Os valores de amônia total (0 a 0,5 mg/L), temperatura da água (23,3 a 30,6ºC), salinidade (17 a 34 g/L), pH (7,8 a 8,4) e oxigênio dissolvido (4,8 a 6,9 mg/L) apresentaram padrão similar entre os tratamentos. A conversão alimentar (1,88, 2,06 e 2,31) e a sobrevivência (100%, 98,9% e 96,3%) foram significativamente melhores nos tratamentos com 3 e 6 peixes/m³. As médias finais de peso (110, 87 e 80 g) e comprimento total (20, 18,5 e 18 cm) apresentaram diferença significativa. A maior taxa de crescimento foi observada com 3 peixes/m³; entre as demais não houve diferença. Entretanto, a biomassa final (332, 511 e 703 g/m³) foi diretamente proporcional à densidade. A baixa densidade favorece o cultivo do robalo em relação ao crescimento, sobrevivência e conversão alimentar.

A new species of Acantholochus Cressey, 1984 (Copepoda: Bomolochidae) parasitic on the gills of common snook, Centropomus undecimalis, from the coastal zone of the State of Rio de Janeiro, Brazil, is described and illustrated. The new species differs from all other species of Acantholochus by the presence of only one inner seta on middle segment of the second and third endopods.

La biología reproductiva y poblacional fue analizada en poblaciones explotadas de robalo blanco Centropomus undecimalis. El material biológico se obtuvo en los desembarcos de la pesca artesanal de las cooperativas de mayor contribución, en volumen y constancia, en la captura del robalo. La longitud estándar, el peso eviscerado y el sexo de 438 organismos se registró mensualmente, durante 19 meses. Las tallas más frecuentes fueron de 70 a 95 cm de longitud estándar. Se encontraron diferencias significativas entre las longitudes de machos y hembras (Kruskal Wallis; p < 0.05). Los machos representaron el 69% y las hembras el 31%, con una proporción macho:hembra de 2.2:1. La proporción total de sexos presentó diferencias significativas (p < 0.05). La relación longitud-peso no difirió entre hembras y machos (ANCOVA p > 0.05). Se determinó una curva de peso eviscerado, Pev = (0.0106) x (LS)2.9595, con un crecimiento isométrico (b = 3). Los máximos valores del índice gonadosomático de hembras se registró en agosto de 2004 (1.56) y julio de 2005 (1.52), y para los machos fue en marzo de 2004 (1.67).

This study examined the effect of a commercial mix of Bacillus sp. on survival, growth and digestive enzyme activities of Florida pompano, red drum and common snook. Larvae were fed either live feed enriched with Algamac 3050 (Control), Algamac 3050 and probiotics ( PB), or the previous diet combined with a daily addition of probiotics to the tank water ( PB+). Survival was not affected by the treatments for any of the species. At the end of the pompano and snook trial, standard lengths of larvae from the PB and PB+ treatments were significantly greater than for the control larvae. Microbiological analyses were performed at the end of the pompano trial, and numbers of presumptive Vibrio were not a concern in the system. For both pompano and snook, trypsin-specific activity was higher in PB and PB+ larvae compared with the control larvae. Similarly, alkaline phosphatase activity was higher for the pompano larvae fed the PB and PB+ treatments and for the snook larvae fed the PB+ treatment compared with the control larvae. This experiment suggests that a mix of Bacillus sp. can promote growth through an early maturation of the digestive system during the early larval stages of pompano and snook. [ABSTRACT FROM AUTHOR]

Acanthocollaritrema umbilicatum Travassos, Freitas and Bührnheim, 1965, is the only species of Acanthocollaritrematidae described up to the moment. The systematic position of this species and the validity of the family has been questioned by the possible presence of a gonotyl and a genital atrium associated to the acetabulum. In this paper, specimens of this trematode, collected from Centropomus undecimalis cultivated at Itamaracá, State of Pernambuco, northeast Brazil, were studied under optical and scanning electron microscopy, and compared with available sintypes. Gonotyl and genital atrium were not observed and both family and species are considered valid taxonomic entities. A. umbilicatum is redescribed with the adition of new morphological information.

The common snook, Centropomus undecimalis, is a migratory euryhaline fish. In the southern Gulf of Mexico, fishing of large snooks occurs mainly in the marine environment (MA), while medium-size adults and juveniles are caught in freshwater environments (FW); however, large-size adults can also be found in FW far away from the sea, and the effect of different environments on their reproductive cycle is unknown. To describe the reproductive cycle of this species in different salinity habitats, we analyzed macroscopic reproductive characteristics during one annual cycle in FW and MA interconnected by the Grijalva-Usumacinta basin. Specimens with full-grown gonads and capable of spawning were found in FW, an unusual condition not reported for this habitat, but active spawning was observed only in MA. Centropomus undecimalis has a biological strategy that allows the use of FW as a juvenile until it reaches sexual maturity as a male and joins the reproductive stock in MA. Adults of both sexes can remain in both FW and MA without affecting their reproductive cycle, suggesting that those that mature in FW migrate to the sea during the spawning season [ABSTRACT FROM AUTHOR]

The Common Snook, Centropomus undecimalis, inhabits riverine and marine areas of Southern Gulf of Mexico, where it is subject to intense use and exploitation. It has been reported that the genetic identification of fish stocks constitutes a valuable tool for wild population management; nevertheless, there is no available information on the genetic identification on fish stocks of this species in the region. The aim of this study was to determine the genetic relationship between C. undecimalis captured in marine and freshwater environments of the Gulf of Mexico and the San Pedro River. For this, muscle tissue samples of 79 specimens were obtained from areas located more than 300km apart. The genotype of each individual was determined using seven microsatellite primer pairs. Five primers amplified efficiently presenting between six and 28 alleles per locus. High levels of heterozygosis were observed in samples from both environments. Deviation from HWE due to an excess of heterozygotes was observed. The values of genetic difference indicate an absence of population structure (FST=0.0075 and RST=0.016, p=0.051) and similarity in the allele frequencies, defined by Nei's index (0.805). Data showed the existence of a high gene flow due to the number of migrants (Nm=18.7). Our results suggest that individuals living in these environments belong to the same genetic population. We suggest the development of management and protection plans for this fish species population in the wild. [ABSTRACT FROM AUTHOR]

Abstract: Applying spatially varied management actions can be a valuable component of an ecosystem-based approach to fisheries management. However, detecting the benefits of spatial management actions can be difficult, especially considering the large spatial range of most fished stocks. The common snook (Centropomus undecimalis) is a premier target species in Florida's estuaries and the fishery is entirely recreational with 96% of the fish caught returned to the water by anglers. However, the management conservation objective of maintaining a spawning potential ratio (SPR) greater than 40% is not always achieved under current regulatory practices. We developed a spatially explicit, age-based, dynamic simulation model to evaluate management actions that could achieve target SPR objectives by incorporating spatial closures. The snook stocks of the east and west coasts of Florida were both assumed to be comprised of three substocks that each occupied a separate estuarine system with limited larval and adult interconnectivity. The model was used to evaluate scenarios incorporating different combinations of closures. A scenario that had partial snook-fishing closures (two systems allowing catch-and-release fishing only and one system also allowing snook harvest) was compared with a scenario in which all three systems had snook harvest. The partially closed scenario attained balanced results with 60% SPR, 54% of the unfished abundance of trophy-size snook, 48% of maximum harvest in numbers, and 51% of maximum yield in weight. In contrast, the fully fished scenario resulted in overfishing with 25% SPR, 15% of the unfished abundance of trophy-size snook, 98% of maximum harvest, and 99% of maximum yield. Certain recreational fisheries may benefit from designation of catch-and-release-only areas in a network of spatially distinct but biologically connected coastal systems. [Copyright &y& Elsevier]

The common snook, Centropomus undecimalis, and the locally called chucumite, Centropomus parallelus, occur naturally in the Gulf of Mexico. They are considered high value species and are regularly exploited in coastal fisheries, particularly in the state of Veracruz (Mexico). In order to study their growth in fresh-water artisanal earthen ponds, fingerlings of about 5.5 cm standard length of both species were captured in Alvarado Lagoon (Veracruz) and stocked in three 25 × 10 × 1.20 m ponds at densities of 4:1, 1:1 and 3:2 (chucumite:snook). Tilapia (Oreochromis niloticus) broodstocks were stocked at the same time to supply live food for the snook and chucumite. During the 14-month experimental period, the absolute growth rates in length and weight were recorded, obtaining maximum values of 26.43 ± 0.135 cm and 265.3 ± 0.623 g for C. undecimalis and of 12.0 ± 0.105 cm and 55.1 ± 0.191 g for C. parallelus; the daily growth rate was 0.062 cm for the former and 0.028 cm for the latter. The length-weight relationship estimated (W = aLb) was 3.01 for C. undecimalis and 2.96 for C. parallelus, presenting isometric growth. The fresh-water culture conditions were monitored throughout the experiment, including temperature (26–34°C), dissolved oxygen (4.1–6.9 mg L–1) and pH (6.9–7.5). The culture conditions used did not have any negative effect on growth, since the lengths and weights attained are within the mean values reported for both species.

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Abstract: Dietary studies are essential for studying trophic dynamics, and are often based on analysis of stomach contents. A popular method to collect stomach contents is the use of pulsed gastric lavage (PGL), wherein a stream of pressurized water forces an individual to regurgitate food items. Most past experimental studies have shown no effect of PGL on survival, but these studies are limited to laboratory or cage experiments, thereby controlling for natural effects such as predation or emigration. Using a mark–recapture/resighting approach, we determined the effect of PGL on apparent survival (ϕ=1−mortality−emigration) in a natural system. In two study sites, we marked a total of 200 juvenile common snook, Centropomus undecimalis (Bloch 1792) (mean=251.7mm standard length, sd=30.7, range=202–320mm) with PIT tags, lavaged 89 of these snook, and resighted 90% of marked fish at least once with a telemetry array. Using the Barker survival model, we determined a significant effect of PGL on apparent survival through QAICc model selection, 95% confidence intervals of parameter estimates, and likelihood ratio testing (P =0.017). The PGL effect reduced QAICc model averaged maximum likelihood estimates of apparent survival by 12.0–17.4%. Since we estimated apparent as opposed to true survival, we could not fully partition lethal and sublethal (emigration) effects; however, a lower incidence of emigration in lavaged individuals suggests that emigration did not drive the declines in apparent survival. Regardless of the mechanism, we found that PGL affected individuals, which is contrary to most previous controlled studies. Future researchers using PGL must consider the influence of potential lethal/sublethal effects in natural settings. [Copyright &y& Elsevier]

Abstract: Studies of fish ecology are enhanced by precise and accurate knowledge of survival, which can be estimated from capture-recapture/resighting based survival probabilities. We conducted a cost-benefit analysis of resighting by an array of 11 autonomous PIT tag antennae and recapture by seine netting, and compared the effectiveness of the two methods for recapturing/resighting marked fish in an estuarine environment. During three separate marking periods, we marked a total of 2109 fish with PIT tags, recapturing 106 by seine (5.0%) and resighting 1700 by antennae (80.6%). Antennae resulted in precise monthly survival estimates while seine netting did not, but antennae did not collect ancillary data (e.g., growth) and their use was limited to areas where fish used constricted passes <10–30m in width. Despite a reliance on seine nets to capture fish for marking and high initial construction costs, the cost-effectiveness of PIT tag antennae (US$45–$57 per unique fish resighted) exceeded that of seine netting (US$167–$934). Considering physical capture was required to mark fish, the use of PIT tag antennae is a dual-method approach incorporating both physical captures and telemetry. This dual-method approach can collect cost-effective and highly detailed data that could enhance our ability to make informed management and conservation decisions. [Copyright &y& Elsevier]

Common snook ( Centropomus undecimalis) is one of the most important marine species under commercial exploitation in the Gulf of Mexico; for this reason, interest in developing its culture is a priority. However, larviculture remains as the main bottleneck for massive production. In this sense, our objective was to determine the changes of digestive enzymes activities using biochemical and electrophoretic techniques during 36 days of Common snook larviculture fed with live preys (microalgae, rotifers, and Artemia). During larviculture, all digestive enzymatic activities were detected with low values since yolk absorption, 2 days after hatching (dah) onwards. However, the maximum values for alkaline protease (6,500 U mg protein), trypsin (0.053 mU × 10 mg protein), and Leucine aminopeptidase (1.4 × 10 mU mg protein) were detected at 12 dah; for chymotrypsin at 25 dah (3.8 × 10 mU mg protein), for carboxypeptidase A (280 mU mg protein) and lipase at 36 dah (480 U mg protein), for α-amylase at 7 dah (1.5 U mg protein), for acid phosphatases at 34 dah (5.5 U mg protein), and finally for alkaline phosphatase at 25 dah (70 U mg protein). The alkaline protease zymogram showed two active bands, the first (26.3 kDa) at 25 dah onwards, and the second (51.6 kDa) at 36 dah. The acid protease zymogram showed two bands (RF = 0.32 and 0.51, respectively) at 34 dah. The digestive enzymatic ontogeny of C. undecimalis is very similar to other strictly marine carnivorous fish, and we suggest that weaning process should be started at 34 dah. [ABSTRACT FROM AUTHOR]

Spawning site fidelity has long been documented for anadromous salmonids, and more recently in estuarine and marine fish. The level of fidelity has implications for population dynamics, conservation, and management. This study extended a previous examination of spawning ground fidelity for common snook, Centropomus undecimalis. We used seines to sample 28 km of Gulf of Mexico beaches, spawning grounds for snook, during spawning season (May through September) from 2007 through 2010. Of 3,304 snook tagged, 171 unique fish were recaptured a total of 186 times and, of those, 166 fish (97.08%) (181 recaptures = 97.31%) were recaptured on the same island where they were tagged. One hundred seven of the recaptures occurred in the same year they were tagged, and 79 occurred one or more years after they were tagged, indicating fidelity was expressed within and across years. Distance between tag and recapture locations within and among years demonstrated fidelity at a spatial scale much smaller than barrier island (mean distance between tag and recapture =1.59 ± 0.12 km; island lengths 6.8, 8.9 and 12.4 km). Furthermore, mapping of capture locations revealed clumped distribution of snook on spawning grounds, further suggesting snook propensity for specific locations. Fish size had no effect on fidelity. We conclude that common snook show a high level of spawning site fidelity in southwest Florida, which may result in spawning group segregation, may influence the response of snook to disturbances, and may have implications for adult-to-nursery ontogenetic connections. [ABSTRACT FROM AUTHOR]

Abstract: Induced spawning of common snook, Centropomus undecimalis (Bloch, 1792) and scale-up of larval rearing is described. Fertilized eggs were obtained from sGnRHa induced broodstock, acclimatized to captivity under natural conditions, for 5years in 12-m3 fiberglass tanks. Females with 402±15μm diameter vitellogenic oocytes were given an implant dose of 121±31μgkg−1 while males received 83±6μgkg−1. A total of 4.33×106 eggs (18.5% floating) resulted from ten natural voluntary spawns. Two 5-m3 cylindrical fiberglass tanks were stocked at an average of 40floating eggsl−1, which resulted in 14larvael−1 at 2days post hatch (dph). A total of 70,936 juveniles were harvested on 45dph (50.7% survival from first feeding). Two critical periods occurred, between 1 and 2dph, and during transformation (20–23dph). Final mean total length and weight at 46dph were 21.26±2.83mm (0.42mmday−1) and 0.07±0.03g (0.002gday−1). Mean final density and biomass were 7.1juvenilesl−1 and 0.479kgm−3. The incidence of deformities was low, less than 2%, mostly lordosis. Improvements for spawning common snook including changes in feeding regime and GnRHa implant doses are detailed along with suggestions for further improvements in mass production technology. [Copyright &y& Elsevier]

In Southeastern Mexico, Centropomus undecimalis is an important fish species of sport and commercial fisheries for coastal and riverine communities. Fisheries along rivers and coasts depend on migratory habits of this species, and these movements are probably related to reproduction. In spite of its economic importance, few studies have been conducted focusing on its reproductive biology, and this research aims to analyze these habits. Samples (fork length, somatic and gonads weight, and macroscopic maturity stages) were obtained from organisms collected by fishermen from the largest fishing cooperatives along the coastal and riverine areas of Tabasco, from July 2006 to March 2008. Fish size ranged from 34 to 112cm fork length, with an average age of 6.42 years for males and 9.12 years for females. In riverine areas, fish sizes ranged from 30 to 85cm and the average age was 5.5 years for males and 6.6 years for females. Significant differences were recorded between lengths of males and females from the two areas (Kruskal-Wallis, p<0.05). The male:female ratio was 1:0.68 in the coast, and 1:0.16 in riverine areas. The length-weight relationship did not vary between both sexes among areas (ANCOVA, p>0.05). A curve for eviscerated weight was calculated for both sexes, for coastal fishes SW=0.0059(FL)3.07, and the riverine ones SW=0.0086(FL)2.98, with an isometric growth (b=3). The period of maximum reproduction was from July to August, with temperatures of 28 to 30°C. A significant correlation between the gonadosomatic index (GSI ) and rainfall was recorded for samples of both males and females from coastal areas (r=0.63, r=0.70) whereas only one positive correlation was recorded for riverine females (r=0.57). The size at first maturity (L50) was estimated at 60cm and 80cm (FL), corresponding to 5.5 and 8.5 years of age, for males and females, respectively. An important proportion of mature females of eight years and older, suggests that these ages contribute significantly to the reproductive biomass. The results indicate that due to changes in the exploitation period, we recommend to protect populations of the common snook. Rev. Biol. Trop. 59 (2): 669-681. Epub 2011 June 01. [ABSTRACT FROM AUTHOR]