Peak Spawning Season Research Articles

Feeding Aspects and Reproductive Biology of Smalltooth Emperor, Lethrinus microdon (Valenciennes, 1830) in the Gulf of Mannar along the Indian Southeast Coast

Background: The Gulf of Mannar, situated on the southeast coast of India, is a unique distinctive productive marine ecosystem and is rich in biodiversity. Its significance stems from the presence of a string of 21 islands spanning 140 km between Rameswaram and Tuticorin, each adorned with a wealth of coral reefs and hosting a variety of ornamental and marine fish species despite their small and uninhabited nature. It is also first Marine Biosphere Reserve in South and South-East Asia, covers approximately an area of 19,000 sq. km. Methods: Fish samples were collected monthly from three major fishing harbours situated in the Gulf of Mannar along the southeast Coast: Thoothukudi Fishing Harbour, Pamban Fishing Harbour and Chinnamuttom Fishing Harbour from December 2022 to November 2023. These species are caught using trawl net, gill net and hook and line and collected specimens were identified using FAO sheets and standard literature. Result: In this study, a total of 405 specimens were collected. The length weight relationship was estimated for male: W = 0.0522.57, r2 = 0.94, female; W = 0.0572.51, r2 = 0.94; and pooled; W = 0.0632.54, r2 = 0.90, respectively. Fulton condition factor (KF) value for male: 1.22, female: 1.33; and pooled: 1.19, respectively. Gonadosomatic index (GSI) of L. microdon was ranged between 1.21-2.21 for male and 1.85-2.31 for female and Gastrosomatic index (GaSI) varied from 1.45-2.37 for male whereas 1.89-4.43 was found for female. Hepatosomatic index (HSI) of L. microdon was ranged between 0.45-2.54 for male while for female was ranged between 1.11-3.21. The male and female (M:F) sex ratio was estimated 1:0.67. The peak spawning season was observed in June to August. The results provide the baseline biology information required to evaluate the fisheries and sustainable management of these underexploited fishes in the Gulf of Mannar ecosystem.

Combining Local Ecological Knowledge (LEK) and Conventional Scientific Knowledge (CSK) for Exploring Nursery Grounds and Spawning Biology of Yellowtail Catfish Pangasius pangasius in the Meghna River Estuary, Bangladesh

ABSTRACTThe yellowtail catfish (Pangasius pangasius) population in Bangladesh is facing imminent threats that led to endangered status. We used conventional scientific knowledge (CSK) and local ecological knowledge (LEK) of fishers (n = 155) to identify nursery grounds and spawning seasons of yellowtail catfish in the Meghna river estuary. Nineteen nursery grounds were pinpointed using fishers' LEK (confluence/influent zone, current, depth, catch data, and turbidity) and later validated by CPUE data. The peak spawning season was identified in July–September based on GSI (gonadosomatic index) and LEK (58.06% of fishers identified the spawning season). Fecundity (810,980 ± 455,679) and condition factor (0.94–1.52) were quantified with CSK. Using CSK and LEK to delineate nursery grounds and spawning season underscores the value of LEK as a tool for fish population management that deserves policy recommendation and wider application.

Study of Hepatosomatic Index, Gonadosomatic Index and Fecundity of Tengra Fish (Mystus gulio)

The tengra fish (Mystus gulio) is an important commercial species found in the coastal regions of West Bengal, India and Bangladesh. M. gulio is an important species within its ecosystem and has significance in local fisheries. Its adaptability to both freshwater and brackish environments makes it a resilient species. This study investigated the hepatosomatic index (HSI), gonadosomatic index (GSI), and fecundity of M. gulio to better understand its reproductive biology. Specimens were collected monthly from the Meghna River estuary between February and June 2023. The GSI was found to be highest in August (9.95±0.15%), indicating the peak spawning season. The HSI showed an inverse relationship with GSI, being lowest in March. Fecundity ranged from 88,495 to 264,104 eggs, with a mean of 171,581±17,855. Fecundity was positively correlated with total length, body weight, and gonad weight. Statistical analysis revealed significant differences in GSI and HSI between sexes and age groups (virgin vs 1+ year). Regression models showed that fecundity was highly dependent on gonad weight (r2=0.809) compared to length (r2=0.047) and weight (r2=0.216). M. gulio is an important brackish water fish with good taste and nutritional value. While it is optimally exploited from the East Coast of India, its culture potential is being explored through polyculture experiments and research on seed production and farming techniques. These findings provide valuable insights into the reproductive dynamics of M. gulio and can inform management strategies for sustainable fisheries. However, further research is needed to fully understand the reproductive biology of this catfish across its range to inform sustainable management strategies.

Vinegar injections can be used safely to control outbreaks of crown-of-thorns starfish Acanthaster cf. solaris during the peak spawning season

Concerns are mounting over the effects of crown-of-thorns starfish (COTS) (Acanthasteridae) outbreaks, prompting the need for integrated management strategies. Although direct control methods are short-term and localized, they remain one of the few operational tools that can be easily implemented by locals. Vinegar injections have recently emerged as a highly effective method; however, their impact on reproductive behavior remains untested. Here, we investigated the short-term spawning response of mature COTS to double injections of household vinegar. First, COTS abundances and reproductive status were monitored during a massive outbreak affecting New Caledonia’s reefs. In situ and laboratory experiments were then conducted to determine whether injected COTS would trigger synchronized spawning among mature individuals in close proximity. Our results indicated that injections had no significant effect on spawning behavior, even in densely populated aggregations (>4000 COTS ha-1). In the field, starfish exhibited ripe gonads with high gamete content (up to 35% of body weight) 3 d after conspecifics were injected. In the laboratory, mature COTS that were held with injected, decaying individuals in a confined volume did not expel their gametes after 2 d. This suggests that vinegar injections could be used at any time, even during peak spawning, without risking synchronized spawning in the affected areas.

Exploring the reproductive features of Clupisoma garua from Ganges River, Bangladesh: insights into eco-climatic factors for sustainable management and advancements in aquaculture practices.

The Garua bacha, Clupisoma garua, holds considerable commercial and nutritional significance as a fish species. This study investigates the relationships between GSI (gonadosomatic index) and eco-climatic conditions, and provides comprehensive insights into several facets of reproduction, such as size at first sexual maturity (Lm), spawning season, peak spawning period, and proposes sustainable management strategies for C. garua in the Ganges River, northwestern, Bangladesh. Since January to December 2017, 570 female individuals have been gathered from the Ganges River using cast nets, gill nets, and square lift nets on a monthly basis. The total length (TL) of the specimens varied from 3.90 to 26.30cm. Lm was estimated as 14.30cm based on the results of the TL vs. GSI, MGSI (modified gonadosomatic index), DI (Dobriyal index), 14.00cm through TL-FL regressions, and 15.18cm depending on Lmax for this species. Furthermore, the spawning period was observed from May to August, peaking in June and July, based on greater GSI, MGSI, and DI values. Throughout the peak spawning season, there was not a significant differ from a value of 100 in the relative weight (WR) of the female species. During the spawning season, a substantial association between temperature and GSI (p = 0.0038); rainfall and GSI (p = 0.0043); DO and GSI (p = 0.0043); pH and GSI (p = 0.0002); and alkalinity and GSI (p = 0.0001) was detected. Analyzing a 55-year data series (1964-2018), it became clear that an increase in average air temperature of 0.0289 °C and a decrease in rainfall of 2.988mm per year might possibly delay the spawning season of this species. As a consequence, the results of this study provide crucial information for developing management strategies to safeguard C. garua populations in the Ganges River and its adjacent ecosystems.

Effect of water quality parameters and climatic influences on reproductive phenology of Macrognathus pancalus in wetland ecosystem: recommending a long-term management approach and conservation policy.

The study conducted an investigation into the reproductive biology of M. pancalus and assessed the influence of water quality parameters and environmental factors on the spawning pattern within the Gajner Beel ecosystem in Bangladesh. A total of 1218 individuals of M. pancalus (46.39% males and 53.61% females) were collected monthly from the Gajner Beel during January to December 2018 using various fishing gears. The total length (TL) of each individual was measured using digital slide calipers, and the whole body weight (BW) was measured using an electronic balance. Fulton's conditions factor (KF) showed significant differences between males and females. The calculated Lm were 11.11 cm, 11.30 cm, and 11.10 cm based on maximum length, gonadosomatic index (GSI), and the logistic model. The spawning season extended from May through August, with June and July being peak months. The average total fecundity was 1495.52 ± 840.24, with a range of 370 to 4069. During peak spawning season, the average temperature and rainfall were 27°C and 370 mm, respectively. Rainfall, dissolved oxygen, total alkalinity, and pH all had a significant (p < 0.01) positive effect whereas temperature and TDS all had a significant (p > 0.01) negative effect on GSI. Annual air temperature in the study area increased by 0.053 °C/year, with a regression coefficient value (r2 = 0.1695), while annual mean rainfall decreased by 5.97mm/year (r2 = 0.076). This research will contribute to the development of conservation and management approaches of Mastacembelidae fish in relation to current climate variability in sub-tropical waters.

Assessment of Sexual Maturity and Spawning Biology of Channa punctata (Bloch, 1793): Conservation and Reproduction

The study was conducted in the freshwater station of the Bangladesh Fisheries Research Institute in Mymensingh between September 2021 and August 2022. Finding the sex ratio, sexual maturity, LWR, reproductive biology, fecundity, and histological examination of gonads of C. punctata were the main objectives of the present study. The correlation between length and weight was determined by analyzing the power function. Both sexes showed positive allometric growth and the correlation between length and weight was TW= 0.011TL3.09 for males and TW= 0.009TL3.11 for females. The mean condition factor for males was 1.09 (0.89 to 1.24), whereas the mean condition factor for females was 1.12 (0.95 to 1.25). In both cases, the condition factor was more than 1, indicating that the physical condition of both sexes was excellent. Among the 329 samples, 142 (43.16%) were male and 187 (56.84%) were female (male: female = 1: 1.32). The chi-square test showed a significant departure from the 1:1 ratio between the number of males and females within the sample months (df = 1, χ2= 0.01, p=0.05). When they reached first sexual maturity (L50), both sexes were of similar size, as evidenced by their lengths of 14.95 cm. The peak spawning season for both sexes was observed in June and July; however spawning season lasted from April to July. According to the study results, July was recorded the highest absolute fecundity (23609), while December recorded the lowest (1998).

Reproductive biology of endemic sailfin silversides fish Telmatherina antoniae Kottelat, 1991 in Matano Lake, South Sulawesi

Sailfin silversides (Telmatherina antoniae) is an endemic species from Matano Lake, South Sulawesi. This study aims to learn about sailfin silversides’ reproductive aspects including sex ratio, length at first maturity, gonad maturity stage, gonad maturity index, fecundity, and egg diameter. Fish samples were taken using multifilament nets from March 2018 until February 2019. A total of 1,792 individuals fish comprises 922 males and 870 females were captured during the study period. The sex ratio was found in a balanced condition with 1.06:1. Length at first maturity for males and females were 48.08-57.73 mm and 56.78-68.55 mm, respectively. Based on sailfin silversides’ gonad maturity stage and maturity index are thought to be year-round spawning with a peak spawning season around March. The reproductive potential of sailfin silversides fish is estimated to be 179–1,690 eggs. Based on the egg diameter distribution, the sailfin silversides fish is classified as a partial spawner.

Reproductive Biology of Striped Snakehead (Channa striata, Bloch, 1793) in Floodplain of Lubuk Lampam, South Sumatra

Striped Snakehead (Channa striata) is one of the fish species inhabiting the flooded floodplain. Currently, the striped snakehead fish population in the Lubuk Lampam floodplain is undergoing a significant decline due to continuous and unregulated fishing activities. To prevent this population decline, there is a need for comprehensive efforts in managing their reproduction. The objective of this study was to investigate the reproductive behavior of striped snakehead fish in the floodplain of Lubuk Lampam, South Sumatra. The research spanned five months, from December 2022 to April 2023, and involved the collection of fish samples from four different floodplain types: river, lebung, lebak kumpei, and rawang. A total of 284 striped snakehead fish were examined, and measurements of length- weight and their reproductive biology were observed. The findings revealed that the sex ratio of striped snakehead fish was skewed toward females, with a ratio of 1:1.7 (females to males). The size at which female striped snakehead fish reach maturity was determined to be 28.5 cm, while male striped snakehead fish matured at 29.30 cm. The peak spawning season for striped snakehead fish occurred in December, coinciding with the rainy season. The spawning grounds for striped snakehead fish were predominantly located in the lebung station in the upper reaches of the Lubuk Lampam Floodplain. Striped Snakehead fish exhibited a partial spawning behavior. Furthermore, these fish demonstrated a relatively high reproductive potential, with fecundity ranging from 5,859 to 30,321 eggs.

Species identification, reproductive biology, and nutritional value of marine shellfish (Meretrix lyrata) in the Bay of Bengal

Meretrix lyrata which is under the family of Veneridae and under the order of Venerida, is a nutritionally and economically important edible mussel in Bangladesh. However, studies on species identification and nutritional value in M. lyrata are scarce. Therefore, a detailed investigation was conducted on (i) species identification of the common edible mussel through DNA-barcoding and morphometrics, (ii) reproductive features, such as size at sexual maturity, spawning, and peak-spawning seasons under different environmental factors, and (iii) nutritional status through proximate analysis of M. lyrata mussel collected from the Bay of Bengal, Bangladesh. The results indicated that the size at sexual maturity for M. lyrata was 4.2 cm and the spawning seasons were significantly affected by the dissolve oxygen and salinity. The study also demonstrated that the spawning of M. lyrata occurred from January to June and December while peak spawning season was May in the Bay of Bengal. The higher protein and moisture contents with lower fat in M. lyrata indicated that are value-added seafood with higher nutritional values for consumers.

Acoustic telemetry reveals the drivers behind estuary–sea connectivity of an important estuarine-dependent fishery species, Pomadasys commersonnii, in the Breede Estuary, South Africa

The spotted grunter Pomadasys commersonnii is an important estuarine-dependent fishery species known to spawn along the east coast (KwaZulu-Natal Province) of South Africa. However, recent evidence suggests that this species also spawns along the southwest coast in the Western Cape Province (WC), which has necessitated the investigation of estuary–sea movements of adult P. commersonnii in the WC, and their link with spawning season and changing environmental conditions. Seasonal gonad maturation of adult P. commersonnii (n = 112) was investigated using histology and the gonadosomatic index. Seven adult P. commersonnii were acoustically tagged and monitored in the Breede Estuary (WC) between November 2016 and March 2020. Tagged individuals spent more time in the estuary (83.5%) than in the adjacent marine environment. Sea trips (n = 90) lasted on average 3.23 (SD 4.55) days (range 1–37 days), with most sea trips (82.6%) having a duration of less than 5 days. The majority of sea trips (>50%) occurred in austral summer, which coincided with the peak spawning season. Increases in estuary water temperatures in summer and river inflow in winter also influenced the presence of tagged fish in the sea. The high degree of residency of P. commersonnii in the Breede Estuary and short sea trips, along with increased frequency of reproductively ripe fish during summer months, supports the conclusion that regional spawning is occurring along the southwest coast. We suggest that management strategies should be put in place to protect the P. commersonnii population along the South African southwest coast, especially during summer, for the recovery of this population.

Population Structure, Exploitation Status, and Prospects of Brown Meagre Sciaena umbra Linnaeus, 1758 From the Turkish Coast of the Black Sea

The brown meagre (Sciaena umbra Linnaeus, 1758) population has experienced dramatic population declines, and it was regionally assessed as “Near Threatened” in the Mediterranean. In this study, the current status of brown meagre populations in the Black Sea was evaluated by estimating growth and mortality rates based on age readings from the otolith. All specimens were collected by commercial trammel nets between March 2019 and February 2020 in the Turkish coast of the Black Sea. A total of 324 brown meagre were sampled during the study period, ranging in age from 0 to 26. The peak spawning season of the species was from June to July. The Von Bertalanffy growth parameters of (L∞ = 54.15, k = 0.14 yr-1, t0 = -3.11) supports previous studies and suggests that brown meagre is a long-lived and slow-growing species. The exploitation ratio of 0.53 for females and 0.47 for males. Life-history features and mortalities indicate that the brown meagre has relatively high fertility but may be undefended to intense fishing pressure. However, the impact of overfishing, pollution and climate change can have increasingly detrimental effects on the overall population size of this population.

Exploitation status and spawning potential ratio of banana prawn (Penaeus merguiensis) after trawling ban in Kaimana, West Papua

Penaeus merguiensis de Man, 1888 is a prawn species with high commercial value and is a potential fisheries resource in Kaimana, West Papua, Indonesia. Formerly exploited by foreign fishing trawlers, the Indonesian government issued a national moratorium of foreign fishing ship licensing and trawling ban in 2014 and 2015, respectively. Consequently, the fishing activities in this area have shifted to local, small-scale vessels using trammel nets. This study aimed to determine the exploitation status and the spawning potential ratio (SPR) of P. merguiensis in Kaimana waters after the moratorium implementation, considering this species’ previous intensive fishing pressure. The study was conducted from April 2018 to December 2020 using 15,227 measurement samples. The optimal fishing season was observed from July to September, while the peak spawning season was detected between August and November. The carapace length (CLc) was significantly increased, suggesting the improvement of the banana prawn population over three years of trawling ban implementation. However, the exploitation rate (E) from 2018 to 2020 was 0.7%, and the SPR was 17%, implying that the prawn stock was still in an overfished condition. Therefore, fisheries management needs to regulate the efforts of trammel net fishers to avoid further fishing pressure in Kaimana waters.

Reproductive biology of yellowfin tuna (Thunnus albacares) in the northcentral U.S. Gulf of Mexico

The reproductive biology of yellowfin tuna (Thunnus albacares) was investigated from fish collected throughout 2000–2017 in the northcentral U.S. Gulf of Mexico (GOM; n = 1135 females, 776 males), predominately from recreational anglers fishing off the Mississippi River (93 %). Histological evidence, along with mean gonadosomatic index (GSI) values, showed that peak spawning occurred from May to August, with the highest mean GSI value for both sexes observed in May (females, 1.52 %; males, 0.57 %). During the reproductive season, the amount of active spermatogenesis in spawning capable males varied monthly as observed by the progression of germinal epithelium (GE) subphases (i.e., early-GE, mid-GE, late-GE), with the mid-GE subphase observed most frequently throughout the peak spawning season. The upper and lower 95 % confidence intervals among length at 50 % maturity (L50) estimates had the largest degree of separation between the physiological (cortical alveoli, L50 =1002 ± 7.18 mm CFL) and functional maturity thresholds (primary or secondary vitellogenesis; L50 =1071 ± 4.89 mm CFL), indicating that the physiological maturity threshold should be used with caution as it may underestimate L50. Using the postovulatory follicle (POF) method, the minimum spawning interval was estimated during peak spawning months for all functionally mature females at 2.10 days, with a minimum of 17.30 % daily spawning. Batch fecundity estimates for 24 females was linearly related to size and ranged from 37,956–6.2 million eggs per batch. These data allow for U.S. GOM reproductive parameter estimates to be incorporated, for the first time, into future Atlantic yellowfin tuna stock assessments done by the International Commission for the Conservation of Atlantic Tunas.

Study of the spawning season of Hilsa, Tenualosa ilisha in Bangladesh

An experiment was carried out on the reproductive biology of riverine populations of Tenualosa ilisha in Bangladesh to identify peak breeding season using gonadal biology and gonadosomatic index (GSI) information, reproductive and fry production potentiality, which will finally lead to development strategies for conservation of Hilsa fish species. Total 480 Samples were collected from Meghna River, Chandpur, from July 2012 to June 2013 and Tentulia River, Barisal from June 2013 to June 2014. Both Total length (TL) and Gonad length (GL) were measured using a measuring scale, and both Body weight (BW) and Gonad weight (GW) were taken using an electric balance. To detect the peak spawning activity of hilsa of the Meghna River and Tentulia River, the GSI and Dobriyal index (DI) were calculated. The mean GSI value for both female and male hilsa of the Meghna River was found to be varied from 4.84±0.63 to 15.31±1.17 and 0.32±0.04 to 1.04±0.08, respectively, with the highest value in October. In the case of the Tentulia River, the mean GSI value for female and male hilsa was found to be varied from 6.33±0.39 to 15.03±0.37 and 0.32±0.03 to 1.00±0.06, respectively, with the peak in October. Mean DI of female and male hilsa of Meghna River, Chandpur was found to be ranged from 3.31±0.23 to 5.15±0.17 and 1.18±0.04 to 1.71±0.03 respectively, and October was the highest. Mean DI value of female and male hilsa of Tentulia River, Barisal varied from 3.63±0.15 to 5.00±0.12 and 1.18±0.04 to 1.70±0.03 respectively, with the peak in October. Both the GSI and DI results of the present study suggested that hilsa has a prolonged spawning season, but major spawning takes place in October–November, with a distinct peak in October, indicating the peak spawning season for hilsa in Bangladesh.

Reproductive Dynamics of Three Important Clupeiform Food Fishes in the Min River Estuary and Its Adjacent Nearshore Waters, China

AbstractReproductive dynamics of three important clupeiform food fishes (Gray’s Grenadier Anchovy Coilia grayii, Osbeck’s Grenadier Anchovy Coilia mystus, and Chinese Gizzard Shad Clupanodon thrissa) were studied in the largest estuary of Fujian Province, China: the Min River estuary and its adjacent nearshore waters. Samples were collected from May 2017 through July 2020 using trammel nets and trawlers. Females were observed to be significantly larger than males for Gray’s and Osbeck’s grenadier anchovies but not for Chinese Gizzard Shad. The overall sex ratios of all three species showed a significant female bias. Gonad histology was applied to determine spawning season, peak spawning season, and length at 50% maturity for females and males. The spawning season of females lasted from April to September (peak spawning season in April–July) for Gray’s Grenadier Anchovy, from March to September (peak in March–June) for Osbeck’s Grenadier Anchovy, and from April to July (peak in May–July) for Chinese Gizzard Shad. Spawning seasons of males were similar to those of females. The estimated SLs at 50% maturity for females and males, respectively, were 11.3 and 9.4 cm for Gray’s Grenadier Anchovy, 12.7 and 10.4 cm for Osbeck’s Grenadier Anchovy, and 12.7 and 11.6 cm for Chinese Gizzard Shad. The spawning grounds for these species were located for the first time: in the Min River estuary for Gray’s Grenadier Anchovy, mainly in the adjacent nearshore waters and extending to the estuary for Osbeck’s Grenadier Anchovy, and mainly in the lower reaches of the Min River and extending to the estuary for Chinese Gizzard Shad. As important food fishes in the region, stocks of these three species have shown certain degrees of overexploitation; therefore, stock assessments and management plans are necessary to achieve their sustainable fisheries.

Reproductive biology of rock oyster, Saccostrea cucullata (Born, 1778) along Aare-Ware rocky shore of Ratnagiri, Maharashtra, India

The present study regarding the reproductive biology of Saccostrea cucullata was carried out from May 2014 to April 2016. The observation has indicated that the peak spawning season is from the month of November to January along the Aare-Ware rocky shore of Ratnagiri. For females, the maximum values of Gonado Somatic Index (GSI) were observed in November 2014 (2.8890) and November 2015 (2.9910), whereas in males, GSI values were maximum in November 2014 (2.1964) and December 2015 (2.1681). During the study, the average male: female sex ratio of 1:1.4 was observed, with a minimum of 1:1 in the month of April 2015 and a maximum (1:1.8) during December 2014, indicating predominance of females in all the months. The size of the first maturity has been estimated to be 22.2 mm which can be utilized for signifying management measures for sustainable utilization of the resource.

Reproductive biology of Heteropneustes fossilis in a wetland ecosystem (Gajner Beel, Bangladesh) in relation to eco-climatic factors: Suggesting a sustainable policy for aquaculture, management and conservation

The stinging catfish, Heteropneustes fossilis (Bloch, 1974) is a commercially important fish species in Asia. This is an important food fish as is enriched with high amounts of protein, iron and calcium. The current research demonstrates the population structure, size at sexual maturity, spawning- and peak-spawning season and fecundity of H. fossilis in an important wetland ecosystem - Gajner Beel in northwestern Bangladesh with an aim of its sustainable conservation through induced breeding and aquaculture practices. A total of 426 stinging catfish captured from the Gajner Beel through monthly sampling from January to December 2019 used in the study. Total length (TL), standard length (SL) and body weight (BW) of individual fishes were measured. The size ranges were with 6.70–24.10 cm TL, 1.37–83.94 g BW. Gonads were removed carefully through ventral dissection and weighted. Lm was 14.02, 13.5, 13.0 and 15.0 cm based on maximum length (Lmax), TL vs. GSI (%), TL vs. SL and logistic model, respectively. Monthly variations of GSI and maturation stages were confirmed in April to August as spawning season and June as peak spawning month. Fulton’s condition factor (KF) was found to be with significant relations with GSI values. Fecundity was 1,730 to 23,870 and significantly correlated with both TL and BW. Temperature has been increasing 0.029 °C/year with the falling of rainfall at 2.96 mm/year in the study area. Environmental factors -Temperature, rainfall, dissolved oxygen and pH were found to be significantly correlated with GSI. We found the optimal range of temperature (29–31 °C), rainfall (350–380 mm), dissolved oxygen (5.0–6.0 mg/l) and pH (7.1–7.5) for spawning of H. fossilis. The paper recommended the policy guidelines to pave the ways of the aquaculture, conservation and management of H. fossilis in the changing eco-climatic events through specific management measures.

An agent‐based model accurately predicts larval dispersal and identifies restoration and monitoring priorities for eastern oyster (Crassostrea virginica) in a Southwest Florida estuary

An agent‐based modeling (ABM) framework was developed to support oyster reef restoration efforts in the Caloosahatchee River Estuary located within the encompassing Charlotte Harbor estuarine system, Southwest Florida. The modeling approach is novel for this shallow estuary which experiences heavily managed freshwater inflow known to be an ecological stressor to the estuary's oysters. The aims of the study were to (1) determine the ABM's accuracy in simulating larval dispersal patterns when compared with measured in situ larval settlement data; (2) establish connectivity patterns between various oyster reefs within the estuary; and (3) discover larval transport pathways within the Charlotte Harbor estuarine system. Key characteristics of the ABM, in particular the agents serving as simulated larvae, include settlement behavior and salinity tolerance and associated mortality. The ABM accurately recreated larval dispersal patterns during the peak spawning season, providing fundamental insight into the importance of protecting the furthest upstream oyster reef as a sustained larval source to the downstream reefs. Thus, supporting the effectiveness of using field measurements for the validation of ABMs and subsequently using ABM simulations to bolster future field studies. Ultimately, this study provides an effective, generally applicable, approach to model larval ecology for restoration purposes.

Assessing reproductive biology of Macrobrachium lamarrei in the Ganges River (NW Bangladesh) in relation to environmental parameters.

Macrobrachium lamarrei (H. Milne-Edwards, 1837) is a well-known freshwater prawn species of Bangladesh. The aim of the research is to explore various reproductive aspects (size at sexual maturity, reproductive period and fecundity) of M. lamarrei in the Ganges River, Bangladesh through October 2012 to September 2013. We also study the environmental parameters and their impact on reproduction of M. lamarrei. A total 391 (ovigerous = 141, non-ovigerous = 250) female specimens were collected using Drag net. The TL50 (the TL at which 50% of individuals become mature) was calculated by a logistic equation as 5.20 cm. Based on the availability of ovigerous females the spawning season was February-November with the peak June-July. Further, 50% and 90% ovigerous females were observed when Fulton’s condition factor (KF) was 0.85 and 1.03, respectively. The total fecundity (FT) was ranged from 65 to 370 where TL was 4.20–6.40 cm and BW was 0.84–2.50 g. Fecundity was found to be highly correlated with TL (r2 ≥ 0.96, rs = 0.96, p < 0.0001) and BW (r2 ≥ 0.88, rs = 0.93, p < 0.0001). Temperature (rp = 0.82, p = 0.009), dissolved oxygen (DO) (rp = −0.83, p = 0.0007), pH (rp = 0.80, p = 0.0014) and total alkalinity (rp = −0.87, p = 0.0002), were highly correlated with ovigerous females. The average temperature on peak spawning season was 32 °C. Also, the spawning period connected with the peak rainfall and showed a notable relation between rainfall and ovigerous females. In addition, exploration of long data series pointed that yearly average air temperature is rising by 0.029 °C yr−1, whereas yearly average rainfall is falling by 2.96 mm yr−1. Therefore, the result will be helpful for the sustainable management and conservation of M. lamarrei through fixed permissible mesh size and establishment of a ban period in the Ganges River, Bangladesh and adjoining ecosystems.