Reproduction ecology of an emerging fishery resource, the amphibious mudskipper Periophthalmus chrysospilos, in the Mekong Delta.

Populations of Periophthalmus chrysospilos, the Gold-spotted mudskipper, within the Mekong Delta are facing extirpation risks due to indiscriminate harvesting for the growing aquarium and food-fish trade. This study provides some of the first information on reproductive ecology-such as spawning type and season, length at first maturity, and batch fecundity-of this species, to be used in their management. The sex ratio of wild populations, based on 1031 individuals (523 males and 508 females) is 1:1. The gonadosomatic index (GSI) values are exhibit a non-normal distribution and changed with gender, season, and site. A combination of GSIs and the monthly appearance of mature gonads suggest that this species reproduces throughout the year, with peak from July to October. This species exhibits sexual and spatial variation in size at first maturity (Lm ) as Lm is 6.2-8.6 cm in males and 6.4-7.3 cm in females. The batch fecundity (F = 2614 to 23,465 eggs/female) exhibits non-normal distribution and varies with site, with the highest values at Dam Doi, Ca Mau (13,336 ± 1,279 SE) and the lowest at Tran De, Soc Trang (6654 ± 851 SE). In addition, batch fecundity is directly proportional to body size due to high determination relationships between batch fecundity and fish size (r 2 > 0.64 for all cases). Information derived on the reproductive biology of this species can inform its conservation, sustainable exploitation, and ex situ propagation.

Batoid Abundances, Spatial Distribution, and Life History Traits in the Strait of Sicily (Central Mediterranean Sea): Bridging a Knowledge Gap through Three Decades of Survey.

Batoid species play a key role in marine ecosystems but unfortunately they have globally declined over the last decades. Given the paucity of information, abundance data and the main life history traits for batoids, obtained through about three decades of bottom trawl surveys, are presented and discussed. The surveys were carried out in two areas of the Central Mediterranean (South of Sicily and Malta Island), in a timeframe ranging from 1990 to 2018. Excluding some batoids, the abundance trends were stable or increasing. Only R. clavata, R. miraletus, and D. oxyrinchus showed occurrence and abundance indexes notable enough to carry out more detailed analysis. In particular, spatial distribution analysis of these species highlighted the presence of two main hotspots in Sicilian waters whereas they seem more widespread in Malta. The lengths at first maturity (L50) were 695 and 860, 635 and 574, and 364 and 349 mm total length (TL), respectively, for females and males of D. oxyrinchus, R. clavata, and R. miraletus. The asymptotic lengths (L∞) and the curvature coefficients (K) were 1365 and 1240 (K = 0.11 and 0.26), 1260 and 1100 (K = 0.16 and 0.26), and 840 and 800 mm TL (K = 0.36 and 0.41), respectively, for females and males of D. oxyrinchus, R. clavata, and R. miraletus. The lack of detailed quantitative historical information on batoids of Sicily and Malta does not allow to analytically judge the current status of the stocks, although the higher abundance of some species within Malta raises some concern for the Sicilian counterpart. In conclusion, suitable actions to protect batoids in the investigated area are recommended.

Reproductive biology of female sawcheek scorpionfish, Brachypterois serrulata (Richardson, 1846) (Teleostei; Scorpaenidae) from Visakhapatnam Coast, India.

We examined the reproductive biology of sawcheek scorpionfish, Brachypterois serrulata, collected from Visakhapatnam fish landing center (fishing area covered 16.98°-20.20°N, 82.19°-86.53°E). We studied the annual reproductive cycle, fecundity, size at first maturity, mode of spawning with periodical changes and histological preparations. Size distribution and size at sexual maturity were calculated as 108 mm TL for females. The mean gonado somatic index values of female increased rapidly from January to December, and reached its peak during January and February. The fecundity of the fish species is determined by the size and weight of the individuals. The fecundity varied from 1896 to 20,488, with an average of 5721.90 ova.

Adjustments in population and reproductive dynamics of native and non-native congeneric species during 26 years after invasion

We aimed to improve the understanding of the establishment of Serrasalmus marginatus (non-native), which was followed by a decrease in the abundance of Serrasalmus maculatus (native) in the upper Paraná River floodplain. We estimated age, mortality rate, length and age at first maturity and variations in gonad development in three time-periods along a 26-year truncated time scale for both species. Population and reproduction parameters of both species showed substantial fluctuations among periods. Most age classes were sampled in all time-periods, but with considerable difference in abundance, with predominance of older individuals in the second time-period and younger individuals in the third time-period for both species. The mortality rates decreased for both species in the second time-period, but increased for the native in the third time-period. Length and age at first maturity decreased in the second time-period for both species, increasing the number of mature individuals on their populations. In the third time-period, the number of immature individuals increased for both species. We suggest that species experienced stressful conditions during cooccurrence and this have resulted in physiological responses in both species, reflecting in population and reproductive adjustments that may have relaxed competitive interactions between them, optimizing survival, reproductive effort and coexistence.(AU)

Nosso objetivo foi aumentar o conhecimento sobre o estabelecimento de Serrasalmus marginatus (não nativa), que foi seguido pela diminuição na abundância de Serrasalmus maculatus (nativa) na planície de inundação do alto rio Paraná. Estimamos a idade, taxa de mortalidade, comprimento e idade de primeira maturação e variações no desenvolvimento gonadal em três períodos ao longo de 26 anos para as espécies. Os parâmetros populacionais e de reprodução das espécies mostraram flutuações substanciais. A maioria das faixas etárias foi amostrada em todos os períodos, mas com diferenças consideráveis na abundância, predominando indivíduos mais velhos no segundo período e indivíduos mais jovens no terceiro período para ambas as espécies. A taxa de mortalidade diminuiu para as espécies no segundo período, mas aumentou para a espécie nativa no terceiro período. O comprimento e a idade de primeira maturação diminuíram no segundo período para as espécies, aumentando o número de indivíduos adultos. No terceiro período, o número de indivíduos imaturos aumentou para ambas as espécies. Sugerimos que as espécies passaram por condições estressantes durante a coocorrência, resultando em respostas fisiológicas que desencadearam ajustes populacionais e reprodutivos que podem ter minimizado a interação competitiva entre elas, otimizando a sobrevivência, o esforço reprodutivo e a coexistência.(AU)

Population dynamics of threadfin porgy Evynnis cardinalis, an endangered species on the IUCN red list in the Beibu Gulf, South China Sea.

Threadfin porgy Evynnis cardinalis is both a dominant fish species and an important fishing target in bottom trawl fisheries in the Beibu Gulf, South China Sea. It was listed as endangered (EN) in a recent International Union for Conservation of Nature (IUCN) red list. Despite its economic importance and endangered status, limited research on its biological characteristics and spatial-temporal distribution has been undertaken this last decade, creating uncertainty in current conservation and management. We analyse this species' spatial distribution characteristics using data from four seasonal bottom trawl surveys in 2014-2015, and report average catch per unit effort to vary seasonally, from 49.1 to 594.5 ind h-1 . Growth, mortality and sexual maturity are reported for four time periods based on data from bottom trawl fishery surveys over 1961-1962, 1998-1999, 2006, and 2014-2015. Length frequency distributions changed from bimodal to unimodal, and the female-to-male ratio increased. Mean body length and length at first maturity decreased, whereas the growth coefficient increased, indicating miniaturization, early sexual maturity and accelerated growth, respectively. We report sparid catch to have first exceeded maximum sustainable yield in 2001, and to have remained overfished from 2010 to 2015. Since the 1980s, low-trophic-level fishes such as E. cardinalis have replaced high-trophic-level fishes such as Crimson snapper Lutjanus erythropterus to become dominant species. As catches have increased substantially, these species have been faced with overfishing, driving the ecosystem into an unstable state.

Reproductive Traits of the Duckbill Sleeper Butis butis (Hamilton, 1822).

Butis butis is a commercially important goby that is widely distributed in Indo-Pacific regions; however, its reproductive biology is poorly characterized. We condcted the present study in estuarine and coastline areas in the Mekong Delta from June 2015 to May 2016 to generate reproductive parameters for this species. The results of data analysis based on a collection of 173 individuals (74 females and 99 males) indicate that the sex ratio of this species is close to 1:1. Mature (stage IV) and ripe (stage V) gonads were found monthly during the study period, suggesting that Butis butis is an iteroparous fish that spawns in a year-round cycle. Male B. butis matures first at 8.97 cm total length (TL), which is longer than females (6.82 cm TL). Butis butis is well adapted to tropical monsoon regions due to its high batch fecundity (46,017 ± 6941 SE), ranging from 15,000 (8.6 cm TL and 5.71 g W) to 78,500 (15.8 cm TL and 42.24 g W) eggs. Batch fecundity increases with fish size due to a strong positive relationship between batch fecundity and fish size (TL and W). These results help fill the knowledge gap on the reproductive biology of Butis butis, and contribute crucial information relevant to sustainable management of fish populations in the study region.

Potencial reprodutivo de Pagrus pagrus (Perciformes: Sparidae) em águas costeiras da província de Buenos Aires (Argentina) e Uruguai (34º-39ºS)

The reproductive potential of red porgy in coastal waters of Buenos Aires Province (Argentina) and Uruguay (34º-39ºS) was studied by means of a macroscopic and histological analysis of the gonads. Length and age at first maturity were determined, and fecundity, spawning frequency and egg quality were estimated. The spawning season extended from spring through summer between October and January with a peak of spawning in December. Length and age at maturity for sexes combined was 24.5 cm TL and 1.54 years, respectively. Batch fecundity ranged from 6,974 (25 cm TL) to 110,725 (39 cm TL) hydrated oocytes and showed significant linear relationships with total length and ovary-free weight. Relative fecundity ranged from 16 to 172 oocytes per female gram (ovary free). Spawning frequency was 58.5% during January 2011, indicating that females spawned once every 1-2 days at the peak of the spawning season. The life history of red porgy in Argentina and Uruguay was characterized by a young age at first maturity and partial, almost daily, spawning in a bounded time period, a life history strategy that would facilitate population expansion or colonization of new areas, and high population recovery rates or growth (r).(AU)

Se analizó el potencial reproductivo del besugo en aguas costeras de la provincia de Buenos Aires (Argentina) y Uruguay sobre la base del análisis macroscópico e histológico de las gónadas. Se determinó la talla y edad de primera madurez sexual y se estimaron la fecundidad, frecuencia de puesta y calidad ovocitaria. Se pudo establecer que la actividad reproductiva del besugo acontece durante primavera-verano, entre octubre y enero, con un pico de desove principal en diciembre. La estimación de la talla y edad de primera madurez para ambos sexos fue de 24,5 cm LT y 1,54 años respectivamente. La fecundidad parcial presentó un ajuste lineal con la talla y el peso de la hembra y varió entre 6.974 (25 cm LT) y 110.725 (39 cm LT) ovocitos hidratados. La fecundidad relativa osciló entre 16 y 172 ovocitos hidratados g-1. Los valores de ambos parámetros presentaron diferencias interanuales. La frecuencia reproductiva, determinada mediante el uso de los porcentajes de hembras con folículos post ovulatorios, fue de 58,5% durante enero de 2011, lo que indica que los desoves ocurren una vez cada 1-2 días. Los resultados hallados indican que el besugo se caracteriza por presentar una edad de primera madurez baja (entre 1 y 2 años), desoves parciales casi diarios pero en un período de tiempo acotado. Este tipo de estrategia podría explicar tasas de recuperación o de crecimiento poblacional (r) altas como así también la ampliación de su área de distribución o la colonización de nuevas áreas.(AU)

Reproductive potential of Pagrus pagrus (Perciformes: Sparidae) in coastal waters of Buenos Aires Province (Argentina) and Uruguay (34º-39ºS)

The reproductive potential of red porgy in coastal waters of Buenos Aires Province (Argentina) and Uruguay (34º-39ºS) was studied by means of a macroscopic and histological analysis of the gonads. Length and age at first maturity were determined, and fecundity, spawning frequency and egg quality were estimated. The spawning season extended from spring through summer between October and January with a peak of spawning in December. Length and age at maturity for sexes combined was 24.5 cm TL and 1.54 years, respectively. Batch fecundity ranged from 6,974 (25 cm TL) to 110,725 (39 cm TL) hydrated oocytes and showed significant linear relationships with total length and ovary-free weight. Relative fecundity ranged from 16 to 172 oocytes per female gram (ovary free). Spawning frequency was 58.5% during January 2011, indicating that females spawned once every 1-2 days at the peak of the spawning season. The life history of red porgy in Argentina and Uruguay was characterized by a young age at first maturity and partial, almost daily, spawning in a bounded time period, a life history strategy that would facilitate population expansion or colonization of new areas, and high population recovery rates or growth (r).

Se analizó el potencial reproductivo del besugo en aguas costeras de la provincia de Buenos Aires (Argentina) y Uruguay sobre la base del análisis macroscópico e histológico de las gónadas. Se determinó la talla y edad de primera madurez sexual y se estimaron la fecundidad, frecuencia de puesta y calidad ovocitaria. Se pudo establecer que la actividad reproductiva del besugo acontece durante primavera-verano, entre octubre y enero, con un pico de desove principal en diciembre. La estimación de la talla y edad de primera madurez para ambos sexos fue de 24,5 cm LT y 1,54 años respectivamente. La fecundidad parcial presentó un ajuste lineal con la talla y el peso de la hembra y varió entre 6.974 (25 cm LT) y 110.725 (39 cm LT) ovocitos hidratados. La fecundidad relativa osciló entre 16 y 172 ovocitos hidratados g-1. Los valores de ambos parámetros presentaron diferencias interanuales. La frecuencia reproductiva, determinada mediante el uso de los porcentajes de hembras con folículos post ovulatorios, fue de 58,5% durante enero de 2011, lo que indica que los desoves ocurren una vez cada 1-2 días. Los resultados hallados indican que el besugo se caracteriza por presentar una edad de primera madurez baja (entre 1 y 2 años), desoves parciales casi diarios pero en un período de tiempo acotado. Este tipo de estrategia podría explicar tasas de recuperación o de crecimiento poblacional (r) altas como así también la ampliación de su área de distribución o la colonización de nuevas áreas.

Population structure and reproduction of a migratory fish Leporinus piau (Characiformes: Anostomidae) in a semiarid tropical reservoir, Brazil / Estructura poblacional y reproducción del pez migratorio Leporinus piau (Characiformes: Anostomidae) en una represa tropical semiárida, Brasil

Abstract:Migratory fishes have been seriously impacted by the building of reservoirs and because of the negative effects of these projects such as the interruption of migratory routes, reduction or elimination of spawning/ feeding areas, and initial development can influence the population structure the migratory fishes, resulting in reduction in abundance. Leporinus piau is migratory fish widely distributed in the watersheds of the Brazilian semiarid and it is of importance for artisanal and sport fishing. The goal of the study was to evaluate the population structure and reproductive dynamics of the migratory species Leporinus piau in the Pau dos Ferros Reservoir, which is located in the semiarid region of Brazil. The CPUE, length structure, length-weight relation-ship, length at first maturity, sex ratio, gonad development and IGS were analyzed. Collections were performed quarterly between February 2011 and November 2012 using gillnets. The captured fish were counted; the standard length (cm) and total weight (g) were measured, and dissected to determine the sex and gonad maturity stage. The rainfall and reservoir water levels were recorded, and their correlations with the reproductive period and CPUE were analyzed. A total 549 individuals were captured. The average CPUE varied between 0.0259 individuals/m2*h (May/2011) and 0.0008 individuals/m2*h (August/2012), and significant differences were observed; however, significant correlations were not observed between rainfall and reservoir levels. The standard length varied between 5.9 cm and 20.7 cm, and the weight varied between 4.16 g and 271.5 g. A histogram analysis revealed that the 5-10 cm standard length class was the most abundant for juveniles and that the 10-15 cm class was the most abundant for adult females and males. The weight-length relationship was best fit by the equation log10Wt = -1.57711 + 3.00707 Log10 Ls, and the species presented isometric growth. The estimated length at first maturity was 12.76 cm. A total of 148 males and 82 females were collected (1.81:1, M:F), and these values were significantly different. The highest GSI was observed in February 2011 for both females (10.69) and males (5.72), and the GSI was significantly and positively correlated with rainfall. We concluded that the L. piau population is established in the reservoir and found that its reproduction period occurred during the rainy season between February and May. Rev. Biol. Trop. 64 (4): 1369-1381. Epub 2016 December 01.

Resumen:Los peces migratorios se han visto gravemente afectados por la construcción de embalses y los efectos negativos de estos proyectos, tales como la interrupción de rutas migratorias, reducción o eliminación de desove / áreas de alimentación. El desarrollo inicial puede influir en la estructura de la población de los peces migratorios, lo que resulta en la reducción en la abundancia de los mismos. El Leporinus piau es un pez migratorio que se encuentra ampliamente distribuido en las cuencas del semiárido brasileño y es de importancia para la pesca deportiva y artesanal. El objetivo del estudio fue evaluar la estructura de la población y la dinámica de reproducción de la especie migratoria Leporinus piau en el embalse Pau dos Ferros, región semiárida de Brasil. La relación estructura de tallas y talla-peso de la CPU la talla de la primera la madurez, proporción de sexos, el desarrollo gonadal y el IGS se analizaron. Con redes de enmalle se llevaron a cabo recolecciones trimestralmente entre febrero 2011 y noviembre 2012. Se contaron los peces capturados; se midieron la longitud estándar (cm) y peso total (g), y se disectaron para determinar el estadio del sexo y la madurez de las gónadas. Los niveles de agua de lluvia y los embalses se registraron y se analizaron sus correlaciones con el período reproductivo y la CPUE. Un total de 549 individuos fueron capturados. La CPUE promedio varió entre 0.0259 individuos/m2 * h (mayo/ 2011) y 0.0008 individuos/m2 * h (Agosto/2012), y se observaron diferencias significativas; sin embargo, ninguna correlación significativa se observo entre los niveles de lluvia y el nivel de la represa. La longitud estándar varió entre 5.9 y 20.7 cm, y el peso entre 4.16 y 271.5 g. Un análisis de histogramas, reveló que la clase estándar de 5-10 cm de longitud fue la más abundante de los jóvenes y que la clase 10-15 cm fue la más abundante de las hembras y machos adultos. La relación peso-talla se ajusta más adecuadamente a la ecuación log10Wt = -1.57711 + 3.00707 Log10 Ls, donde la especie presenta un crecimiento isométrico. La medida estimada de la primera madurez fue 12.76 cm. Se recogieron un total de 148 machos y 82 hembras (1.81: 1, M: F), y estos valores fueron significativamente diferentes. El más alto GSI se observó en febrero 2011, tanto para las mujeres (10.69) como para hombres (5.72), y el GSI fue significativa y positivamente correlacionado con la precipitación. Se llegó a la conclusión de que la población L. piau está establecida en la represa y encontramos que su periodo de reproducción se produjo durante la época de lluvias entre febrero y mayo.

Relative yield-per-recruit and management strategies for Cynoscion acoupa (Perciformes: Sciaenidae) in Lake Maracaibo, Venezuela

Acoupa weakfish, Cynoscion acoupa, in Lake Maracaibo is subject to intense commercial fishing by an artisanal fleet, and a recent decrease in fish size observed from landings is of concern. This fishery has not yet been modeled, and its assessment and the establishment of management practices to overcome the current overfished condition are urgently needed. To address this, we used recent and past empirical growth estimates to model relative yield-per-recruit under different lengths at first capture. Our results from relative yield-perrecruit analysis showed evidence that growth and recruitment overfishing occur under current fishing practices in Lake Maracaibo. Particular attention was given to fishing practices in El Tablazo Bay where young, small fish predominate in the commercial catches (mean total length=33.7cm), well below the length at first sexual maturity (~40cm TL) for both sexes. As management strategies, we propose to set a mesh size limit at or above 8.89cm (3.5in), which will reduce fishing mortality of immature fish, increase yield-per-recruit, and will result in an increase of Acoupa weakfish recruitment for the long term in Lake Maracaibo.

La curvina, Cynoscion acoupa, en el Lago de Maracaibo se encuentra sometida a una intensa actividad pesquera comercial. No obstante, antes de este estudio no se había examinado el potencial efecto de la sobrepesca a través del modelado. Utilizamos estimados empíricos de crecimiento actuales y pasados para modelar el rendimiento-por-recluta relativo bajo diferentes longitudes de primera captura. Presentamos evidencia a partir de resultados de rendimiento-por-recluta relativo que indica que existe sobrepesca por crecimiento y reclutamiento bajo las prácticas pesqueras actuales en el Lago de Maracaibo. Se puso particular atención a las pesquerías en la Bahía El Tablazo donde predominan peces jóvenes pequeños en las capturas (longitud total promedio=33.7cm), muy por debajo de la longitud de primera madurez sexual (~40cm LT) para ambos sexos. Proponemos establecer un tamaño de malla igual o superior a 8.89cm (3.5in), el cual reduciría la mortalidad por pesca de peces inmaduros, aumentaría el rendimiento-por-recluta y a largo plazo aumentaría el reclutamiento de la curvina en el Lago de Maracaibo.