Non-spawning Season Research Articles

FACTORS AFFECTING THE INCOME OF FISHERMEN OF SERAYA ISLAND BATAM CITY IN THE SPAWNING SEASON OF DINGKIS (Siganus sp.)

One of the fish commodities that has great potential to be utilized by the fishermen of Seraya Island is Dingkis (Siganus sp.). During the spawning season, Dingkis experience a high price increase of 5 times the price during the non-spawning season, namely IDR 30,000-60,000/kg. Therefore, Seraya Island fishermen take advantage of this opportunity because Dingkis fish only spawn during a certain season, namely January-February, which coincides with Chinese New Year (Imlek). The aim of the research is to determine the income of Seraya Island fishermen during the Dingkis spawning season and the influence of the price of Dingkis, the number of Dingkis fish caught, and the number of other fish catches on the income of Seraya Island fishermen. The research was conducted on Seraya Island, Batu Legong Village, Bulang District, Batam City in February 2023. Data analysis was used to answer the first objective, namely by calculating income, the second objective was to test the influence of the independent variable on the dependent variable using SPSS type 26 software. The research results show that the average income of Seraya Island fishermen during the Dingkis spawning season is IDR 9,001,143/month. Partial test results on the number of catches of Dingkis fish have an effect on the income of Seraya Island fishermen. The price of Dingkis fish and the number of other fish caught have no influence on the income of Seraya Island fishermen.

Seasonal habitat utilization provides evidence for site fidelity during both spawn and non-spawning seasons in Lake Ontario cisco Coregonus artedi

The Lake Ontario cisco Coregonus artedi population declined in the 20th century, and restoration of this species is a management objective. Management tools to restore cisco are limited because little is known about cisco spawning behavior and habitat use. We tagged 76 cisco from a remnant population in Chaumont Bay, Lake Ontario with acoustic transmitters and characterized seasonal habitat use from 2016 to 2021. We also used fine-scale acoustic telemetry, coregonine egg collections, and trap net catches to better understand cisco spawning behaviors related to spawn timing and site selection. Network analysis and Bayesian standard ellipse area indicated that cisco utilization of lake regions and bathythermal niche space varied by season. During spawning season, male cisco concentrated in Chaumont Bay over shallow (∼3 m) rocky shoals where cisco egg deposition was the greatest. Spawning site fidelity to Chaumont Bay was observed for all male cisco surviving to successive years (n = 23). Acoustic-tagged females did not survive consecutive spawning seasons, but trap net catches indicated females were less abundant and occupied spawning areas for less time than males. Post spawn, some individual male cisco (n = 5/23) had differential, yet consistent, annual migrations to separate regions of Lake Ontario, suggesting fidelity to feeding sites. Our results reveal seasonal habitats used by male cisco and, importantly, caution that environmental changes to a single spawning site could negatively affect the remnant Chaumont Bay cisco population. Specialized conservation efforts may be necessary when cisco spawning aggregations have diverse post-spawn migratory behaviors but a central spawning ground.

Reproductive Tract Morphometry and Evaluation of Fresh Wild African ‎Catfish (Clarias gariepinus) Milt from Lake Alau, Maiduguri, Nigeria‎

Reproductive morphometry of Clarias gariepinus (C. gariepinus) is essential in distinguishing different species that are closely related to it and adequate information is required regarding the seasonal variation of milt characteristic of wild species. This study was designed to document the reproductive tract morphometric dimensions and milt characteristics of wild C. gariepinus during spawning and non-spawning seasons in Lake Alau, Maiduguri, Nigeria. Sixty male brood stocks were used comprising thirty each for spawning and non-spawning seasons. The reproductive tracts were removed and their dimensions measured. The milt samples were collected, pooled and evaluated. Results of the study showed that the body weight, sperm concentration and testicular indices differed significantly (p˂0.05) between the two seasons of evaluation. In addition, a positive correlation (p˂ 0.05) between body weight of fish and milt volume (r = 0.656 and r = 0.646) was also observed in both seasons. It was concluded that the left testis of C. gariepinus is heavier, longer and thicker than the right. Nonetheless, the C. gariepinus had larger body weights and higher spermatozoa concentration in spawning season than in non-spawning season; those with larger body weights had higher volume of milt than those with lower body weights.

The Ovarian Transcriptome at the Early Stage of Testis Removal-Induced Male-To-Female Sex Change in the Protandrous Black Porgy Acanthopagrus schlegelii.

Unlike gonochoristic fishes, sex is fixed after gonadal differentiation (primary sex determination), and sex can be altered in adults (secondary sex determination) of hermaphroditic fish species. The secondary sex determination of hermaphroditic fish has focused on the differences between testicular tissue and ovarian tissue during the sex change process. However, comprehensive studies analyzing ovarian tissue or testicular tissue independently have not been performed. Hermaphroditic black porgy shows a digonic gonad (ovarian tissue with testicular tissue separated by connective tissue). Protandrous black porgy has stable maleness during the first two reproductive cycles (<2 years old), and approximately 50% enter femaleness (natural sex change) during the third reproductive cycle. Precocious femaleness is rarely observed in the estradiol-17β (E2)-induced female phase (oocytes maintained at the primary oocyte stage), and a reversible female-to-male sex change is found after E2 is withdrawn in <2-year-old fish. However, precocious femaleness (oocytes entering the vitellogenic oocyte stage) is observed in testis-removed fish in <2-year-old fish. We used this characteristic to study secondary sex determination (femaleness) in ovarian tissue via transcriptomic analysis. Cell proliferation analysis showed that BrdU (5-bromo-2′-deoxyuridine)-incorporated germline cells were significantly increased in the testis-removed fish (female) compared to the control (sham) fish (male) during the nonspawning season (2 months after surgery). qPCR analysis showed that there were no differences in pituitary-releasing hormones (lhb and gtha) in pituitary and ovarian steroidogenesis-related factors (star, cyp11a1, hsd3b1, and cyp19a1a) or female-related genes (wnt4a, bmp15, gdf9, figla, and foxl2) in ovarian tissues between intact and testis-removed fish (2 months after surgery). Low expression of pituitary fshb and ovarian cyp17a1 was found after 2 months of surgery. However, we did find small numbers of genes (289 genes) showing sexual fate dimorphic expression in both groups by transcriptomic analysis (1 month after surgery). The expression profiles of these differentially expressed genes were further examined by qPCR. Our present work identified several candidate genes in ovarian tissue that may be involved in the early period of secondary sex determination (femaleness) in black porgy. The data confirmed our previous suggestion that testicular tissue plays an important role in secondary sex determination in protandrous black porgy.

High fitness areas drive the aggregation of the sea urchin Mesocentrotus nudus.

Sea urchin aggregation is a common phenomenon in coastlines. However, it remains controversial whether sea urchins form resource aggregations or behavioral aggregations in a non-spawning season. To clarify, we studied the aggregative responses to food and predators in the sea urchin Mesocentrotus nudus when high fitness areas (HFAs) were scarce versus sufficient. By taking the occupied area of each sea urchin (test diameter + spines = 4.5 cm) as a square (4.5 cm × 4.5 cm), we set scarce HFAs for the sea urchins in Experiment 1 (the squares of HFAs: the area occupied by experimental sea urchins = 1:1) and sufficient HFAs for the sea urchins in Experiment 2 (the squares of HFAs: the area occupied by experimental sea urchins = 2:1). If M. nudus form resource aggregations, they would aggregate passively under the scarce HFAs conditions, but not in the sufficient HFAs conditions. Conversely, if M. nudus form behavioral aggregation, aggregation would occur in both scarce and sufficient HFAs. The present results showed that in the scarce HFAs, M. nudus in the food and predator groups were significantly closer to the food and further from predators, and had significantly more aggregated numbers in HFAs than those in the control group. Sea urchins did not aggregate in response to food or predators under the sufficient HFAs, although significantly more sea urchins of the experimental group was found in HFAs than that of the control group. Sea urchins (at least M. nudus) form resource aggregations that are driven by the scarce HFAs. This provides valuable information into the mechanisms of the aggregation of sea urchins.

Distribution of adult fish and spawning nests of estuarine-dependent amphidromous goby (

Adults of the marine-originated amphidromous goby (Gymnogobius petschiliensis) inhabit both freshwater and brackish-water areas, unlike many other amphidromous species, which spend their entire lives, except the larval stage, in freshwater. Furthermore, adult G. petschiliensis individuals incur higher osmoregulatory costs in freshwater than those in hypertonic brackish water under laboratory conditions, suggesting that the ecology of the species is largely dependent on high-salinity (ancestral) environments. Therefore, a detailed information on the ecology of G. petschiliensis will help elucidate the diversity and evolution of amphidromy. Here, this study assessed the habitat use and freshwater dependency of G. petschiliensis in two streams in central Japan. Year-round surveys showed that adult density was higher in freshwater than in brackish water during the non-spawning season. This implies that adults chose salinity habitats according to ecological conditions (e.g. inter- and intraspecific competition, and predation risk) without being bound by physiological preferences. Conversely, most egg clutches were found in brackish water. Furthermore, adult density in brackish water increased with the increase in spawning events, suggesting that the adults migrated downstream for spawning. This preference for spawning in brackish water rather than in freshwater may be attributed to the constraints of their reproductive physiology.

Development of a Quantitative PCR Assay for Four Salmon Species Inhabiting the Yangyangnamdae River Using Environmental DNA.

Simple SummaryRegular surveys provide essential information to establish strategies for the effective conservation of salmon resources. As an alternative to conventional fish surveys, which are costly and laborious, quantitative PCR (qPCR) assays were established for the analysis of four salmon species inhabiting the Korean Peninsula. We designed four species-specific primer sets that showed high specificity and sensitivity in both tissue and environmental DNA (eDNA) samples collected from the Yangyangnamdae River. After normalization for PCR inhibition in each sample, the established qPCR assays produced standardized and realistic eDNA profiles for the four salmon species, suggesting that the newly developed qPCR assays are a useful tool for the management of Oncorhynchus resources in Korean waters.A species-specific quantitative PCR (qPCR) assay using environmental DNA (eDNA) is a promising tool for both qualitative and quantitative analyses of target species directly from water samples. Despite its reliability, an eDNA-based qPCR assay pipeline has not yet developed to monitor salmon species inhabiting Korean waters, which have been rapidly decreasing. We designed species-specific primers for four Oncorhynchus species inhabiting the eastern coastal waters along the Korean Peninsula. These include primers for two native species (Oncorhynchus keta and O. masou) and two that were introduced (O. mykiss and O. kisutch). The limit of detection and limit of quantification for the four qPCR assays ranged from 4.11 to 10.38 copies and from 30 to 81 copies, respectively, indicating a high sensitivity and specificity across all four species. Following optimization, the qPCR assays were used for the quantitative analyses of the four Oncorhynchus species in the Yangyangnamdae River during the spawning and non-spawning seasons in the year 2019–2020, one of the main rivers where salmon migrate during the spawning season in Korea. The raw copy numbers in all of the examined samples were normalized by PCR inhibition rates to standardize and compare with other studies. Among the four Oncorhynchus species examined, the eDNA concentration of O. keta increased significantly (63.60-fold, p < 0.0001) during the spawning season (November) compared with that in the non-spawning season (March), suggesting that O. keta is the main salmon species migrating through the Yangyangnamdae River. In contrast, we did not detect any differences in eDNA concentration for the other three Oncorhynchus species between the spawning and non-spawning seasons, indicating that their presence does not alter during the year. Their eDNA concentration is also relatively low compared to O. keta, which suggests that small numbers of these three species are present in the river. Overall, these newly developed qPCR assays represent useful monitoring tools for the management of four salmon species in Korean waters.

Reproductive biology of hardhead catfish Ariopsis felis: evidence for overwintering oocytes.

Hardhead catfish Ariopsis felis are a common marine catfish in the coastal waters of the Gulf of Mexico (GOM). The low economic value of this species has depressed interest and research, and although the species is known for its extremely low fecundity and large oocytes, little else is known about this catfish species. A total of 1230 samples across all months of the year from 2016 to 2018 resulted in 681 females, and analysis of gonado-somatic index (IG ) revealed 1% to be a clear cut-off indicating maturity. Females are considered capable of spawning from April to June when IG averaged 4-8%. Both atresia and post-ovulatory follicles were present in July, suggesting that spawning ends in July in the northern GOM. The 1% IG cut-off was used to designate maturity, and from that an L50 of 253 mm was estimated. Batch fecundity from 41 females estimated a mean batch size of 36 oocytes. Perhaps the most interesting finding was the presence of secondary growth stage oocytes (e.g., cortical alveoli) from July through November, well outside the spawning capable period. Furthermore, 78% of females had some early vitellogenic oocytes present during the non-spawning season, and the distribution of these relatively large (2-5 mm) oocytes did not change over time. The results here are not only important as reproductive biology information for a common and abundant species, but also present interesting and unusual patterns of non-spawning season oocyte development that is not commonly seen in Western Hemisphere subtropical fish species.

Relationships between Pacific salmon and aquatic and terrestrial ecosystems: implications for ecosystem-based management.

Pacific salmon influence temperate terrestrial and freshwater ecosystems through the dispersal of marine‐derived nutrients and ecosystem engineering of stream beds when spawning. They also support large fisheries, particularly along the west coast of North America. We provide a comprehensive synthesis of relationships between the densities of Pacific salmon and terrestrial and aquatic ecosystems, summarize the direction, shape, and magnitude of these relationships, and identify possible ecosystem‐based management indicators and benchmarks. We found 31 studies that provided 172 relationships between salmon density (or salmon abundance) and species abundance, species diversity, food provisioning, individual growth, concentration of marine‐derived isotopes, nutrient enhancement, phenology, and several other ecological responses. The most common published relationship was between salmon density and marine‐derived isotopes (40%), whereas very few relationships quantified ecosystem‐level responses (5%). Only 13% of all relationships tended to reach an asymptote (i.e., a saturating response) as salmon densities increased. The number of salmon killed by bears and the change in biomass of different stream invertebrate taxa between spawning and nonspawning seasons were relationships that usually reached saturation. Approximately 46% of all relationships were best described with linear or curved nonasymptotic models, indicating a lack of saturation. In contrast, 41% of data sets showed no relationship with salmon density or abundance, including many of the relationships with stream invertebrate and biofilm biomass density, marine‐derived isotope concentrations, or vegetation density. Bears required the highest densities of salmon to reach their maximum observed food consumption (i.e., 9.2 kg/m2 to reach the 90% threshold of the relationship’s asymptote), followed by freshwater fish abundance (90% threshold = 7.3 kg/m2 of salmon). Although the effects of salmon density on ecosystems are highly varied, it appears that several of these relationships, such as bear food consumption, could be used to develop indicators and benchmarks for ecosystem‐based fisheries management.

Effects of non-spawning season (yolkless to early yolk formation stage) temperature on growth and reproductive characteristics in hatchery-reared, repeat-spawning walleye pollock Gadus chalcogrammus

The effects of water temperature during the non-spawning season (yolkless to early yolk formation stage of the ovary) on the growth and reproductive characteristics of 4-year-old hatchery-reared walleye pollock Gadus chalcogrammus (repeat spawners) were examined. Fish were kept in tanks under two temperature regimes (non-controlled: 6.4–17.2 °C; cooled: 5.1–15.7 °C) from 42 to 46 months post-hatching (non-spawning period) and showed differences in growth (in terms of weight and condition factor) shortly before the spawning period (mostly at the early yolk formation stage of the ovary). The fish spawned spontaneously from 47 to 51 months post-hatching at 5 °C. Growth differences were related to egg diameter but not to the timing of spawning. Larger eggs were spawned from fish that had greater increases in weight and condition during the non-spawning season. In contrast, the main spawning period did not vary according to the non-spawning season treatment. These results were compared with the spawning records of 2- and 3-year-old walleye pollock from two previous years, showing that the timing of spawning advances as fish size increases with age. In addition, spawning experience and the amount of energy acquired before the spawning period likely influence egg size.

Fatty acid composition and parasitism of European sardine (Sardina pilchardus) and anchovy (Engraulis encrasicolus) populations in the northern Catalan Sea in the context of changing environmental conditions.

The status of sardine and anchovy populations in the northern Mediterranean Sea has been declining in recent decades. In this study, fatty acids and parasitism at different reproductive and feeding stages in these two species were assessed using specimens caught along the northern Catalan coast, in order to assess the links between lipid dynamics, reproduction and feeding in these two species and to contribute towards an explanation of the potential causes of the current poor situation of the stocks. The results support the use of fatty acid levels as indicators of the body condition of sardine and anchovy at different reproductive and feeding stages, as well as that of the pelagic environmental conditions. In particular, the relatively low n-3 polyunsaturated fatty acid levels found in spawning sardines compared to spawning anchovies indicate a poorer reproductive health status of sardine. By comparing the current total lipid content values with those recorded in other Mediterranean and North Atlantic areas, and others from more than 10years ago, in the adjacent area of the Gulf of Lion, our study reveals the persistent poor condition of sardine and anchovy in the northern Catalan Sea. Furthermore, the low levels of diatom fatty acid markers observed throughout the spawning and non-spawning seasons in both sardine and anchovy indicate a diet poor in diatoms. Moreover, the results indicate that it is very unlikely that parasitism is a significant factor in the decline in condition of sardine and anchovy in the northern Catalan Sea. In fact, the results, which we believe provide useful insights for the management of small pelagic fisheries in the Mediterranean, suggest that the current poor condition of sardine and anchovy in the northern Catalan Sea has probably been exacerbated by a decrease in plankton productivity and/or a shift in the taxonomic composition of phytoplankton communities, adding to the ongoing effects of overfishing.

Sex discrimination of cultured greater amberjack Seriola dumerili using steroid hormones

The aquaculture of greater amberjack Seriola dumerili is of considerable research interest worldwide. The larviculture methods employed to culture this species, however, are still under development, and the majority of farms still rely on wild-caught juveniles. One of the problems associated with the hatchery production of this species is the optimal selection of broodstock to ensure a stable supply of high-quality eggs. Specifically, no reliable low-stress sex-discrimination technique is currently available for selecting broodstock of this species. This study investigated the efficacy of a hormone-based sex-discrimination method in full-cycle cultured S. dumerili, ranging in age from 412 to 1150 days after hatching (DAH). Plasma concentrations of the female hormone 17β-estradiol (E2) and the male hormone 11-ketotestosterone (11-KT) were measured in both spawning and non-spawning seasons, and the optimal threshold levels for sex discrimination were estimated using a receiver operating characteristic curve. Sex discrimination using E2 produced several false positives in younger fish, and had an overall accuracy of 78.7%. However, sex discrimination using 11-KT had an accuracy of 96.7%, even in 412 DAH fish. This study demonstrated that sex discrimination using 11-KT is a reliable method for optimizing the sex ratio of S. dumerili broodstock, even before the broodstock mature.

Interspecies Peculiarities of Some Enzyme Activities in the Gonads of Black Sea Fish

Significant interspecies differences were established in activities of aminotransferases, alanine aminotransferase (ALT, EC 2.6.1.2) and aspartate aminotransferase (AST, EC 2.6.1.1), and alkaline phosphatase (ALP, EC 3.1.3.1) in the gonads of seven Black Sea fish species during spawning and non-spawning seasons. In most species, ALT and AST activities were higher in the non-spawning phase compared to the spawning one, while ALP activity demonstrated an opposite trend. The peak enzymatic activities were found in the gonads of the whiting, probably due to its spawning in the winter season. No significant differences were revealed between the test parameters in animals of different ecological groups. ALT, AST and ALP activities in fish gonads can be used as convenient and efficient markers to explore both the peculiarities of the gonadogenesis at different stages of the reproductive cycle and the ability of different fish species to adapt to unfavorable environments, including those caused by anthropogenic pollution.

Two sympatric, not externally discernible, and heavily exploited deepwater species with coastal migration during spawning season: implications for sustainable stocks management of Aphanopus carbo and Aphanopus intermedius around Madeira

Several artisanal fisheries target deepwater species. These stocks are highly sensitive to overfishing because of their slow growth and late maturation. This vulnerability is higher if species concentrate during spawning season in coastal areas, as occur with scabbardfish (Aphanopus spp.). In this paper, we explore if two Aphanopus species (A. carbo and A. intermedius) that coexist show migration patterns to coastal areas during spawning. We analysed specimens of both species throughout 4 years (2014–2017) in a weekly basis and compare morphological parameters with the distance of the coast (coastal (&lt;12 n.m.; 1 n.m. = 1.852 km) versus offshore (&gt;12 n.m.)). Both species showed coastal patterns of migration during the spawning season (October–December), with 65.90% of total specimens of A. carbo and 51.60% of A. intermedius being caught at &lt;12 n.m. during this season. Fishing events were also more numerous at &lt;12 n.m. to the coast during spawning season (46.6%) relative to nonspawning season (32.6%). A series of management measures (e.g., October–December season) were developed to preserve Aphanopus stocks in the Northeast Atlantic Ocean.

Change of Various Characteristics between Spawning and Non-spawning Season in Diploid and Induced Triploid Far Eastern Catfish, Silurus asotus.

ABSTRACTThe purpose of this study is to investigate the differences fatty acids and hormonal parameters in the spawning and non-spawning season between the diploid and induced triploid Far Eastern catfish, Silurus asotus. The measured triploids were produced by cold shock for 50 min at 4℃ in May 2014, the spawning season of diploid was in May, and the non-spawning season was designated in January. Estradiol and testosterone and gonadosomatic index of diploid were higher than those of induced triploid in spawning season (P<0.05), and those of diploid in spawning season were higher than non-spawning season. On the other hand, thyroid stimulating hormone and thyroxine of induced triploid were higher than those of diploid in spawning season (P<0.05). Erythrocyte count of diploid was higher than that of induced triploid in spawning season and non-spawning seasons. Mean corpuscular volume and mean corpuscular hemoglobin of induced triploid were higher than those of diploid in both seasons (P<0.05). Percentages of total saturated fatty acids and n-3 polyunsaturated fatty acids of induced triploid were higher than those of diploid in spawning season, but those of diploid were higher in non-spawning season (P<0.05). Percentages of total mono unsaturated fatty acids and total n-6 polyunsaturated fatty acids of diploid were higher than those of induced triploids in spawning season, while those of induced triploid in non-spawning season were higher (P<0.05). Therefore, induced triploids in the spawning season tend to concentrate on growth and lipid-synthesization, whereas, diploids concentrate on reproduction and gonadal maturation rather than on growth. In non-spawning season, growth and lipid-synthesization were not significantly different between diploid and induced triploid.

복섬, Takifugu niphobles의 산란기 및 비산란기에 따른 성적이형 비교

A closely associated set of characteristics was analyzed using both classical and truss dimensions to discriminate sexual dimorphism between spawning season and non spawning season in grass puffer, Takifugu niphobles. In non-spawning season, 1×10/Ls of classical dimension was significantly different between male and female (P0.05). In spawning season, 1×9/Ls and 1×10/Ls of classical dimension, 3×8/Ls, 3×9/Ls, 3×10/Ls, 4×8/Ls, 4×9/Ls and 8×9/Ls of truss dimension and 7×9/HL of head part dimension were significantly different between male and female (P0.05). The results of this study may be useful as basic information of other fish species to compare the change of sexual dimorphism between spawning season and non spawning season.

Movement patterns and spatial segregation of two populations of lake trout Salvelinus namaycush in Lake Huron

Abstract Movement ecology is an important component of life history and population dynamics, and consequently its understanding can inform successful fishery management decision-making. While lake trout populations in Lake Huron have shown signs of recovery from near extinction in recent years, knowledge of their movement behavior remains incomplete. We used acoustic telemetry to describe and compare movement patterns of two Lake Huron lake trout populations: Drummond Island and Thunder Bay. Both populations showed high spawning site fidelity, with no evidence of co-mingling during non-spawning season. Detections between spawning periods were mainly limited to receivers within 100 km of spawning locations, and suggested that the two populations likely remained segregated throughout the year. Drummond Island fish, which spawn inside the Drummond Island Refuge, primarily dispersed east into Canadian waters of Lake Huron, with 79–92% of fish being detected annually on receivers outside the refuge. In contrast, Thunder Bay fish tended to disperse south towards Saginaw Bay. Large proportions (i.e., > 80%) of both populations were available to fisheries outside the management zone containing their spawning location. Thunder Bay fish moved relatively quickly to overwinter habitat after spawning, and tended to repeat the same post-spawning movement behavior each year. The consistent, predictable movement of both populations across management zones highlights the importance of understanding population dynamics to effective management of Lake Huron lake trout.

Male organs of African catfish (&lt;i&gt;Clarias gariepinus&lt;/i&gt;) in spawning and non-spawning periods in Maiduguri, Borno State, Nigeria

The study was undertaken to investigate the gross reproductive organs of wild male Clarias gariepinus in spawning and non-spawning periods. Twenty mature males of C. gariepinus comprising of ten each during both periods were used. They weighed an average of 532 ± 8.32 gm during spawning and 510.8 ± 9.27 gm during non-spawning season and measured a standard body length of 43.2±4.72 cm and 42.1±2.48 cm during spawning and non-spawning seasons respectively. All fish were sourced from Gamboru fish market, Maiduguri and transported live to the gross Anatomy laboratory, Department of Veterinary Anatomy University of Maiduguri. Each fish was euthanized using tricaine anaesthetic at 8 drops/litre of water. The reproductive organs were removed en mass using scalpel, forceps, and scissors. Then the number of seminal vesicles were determined during spawning (37.8 ± 4.53) and non-spawning (36.32 ± 3.68) periods. The organs were seen consisting of lobular testes, milt duct, seminal vesicles, bulbourethral gland and papilla, which are whitish and milky colour appearances in spawning and non-spawning periods respectively. The milt duct which have the paired and unpaired part were also seen clearly in non-spawning period but relatively invisible in spawning period.Keywords: Bulbourethral gland, Maiduguri, seminal vesicles, testes, Wild African catfish

Restricted grouper reproductive migrations support community-based management.

Conservation commonly requires trade-offs between social and ecological goals. For tropical small-scale fisheries, spatial scales of socially appropriate management are generally small—the median no-take locally managed marine area (LMMA) area throughout the Pacific is less than 1 km2. This is of particular concern for large coral reef fishes, such as many species of grouper, which migrate to aggregations to spawn. Current data suggest that the catchment areas (i.e. total area from which individuals are drawn) of such aggregations are at spatial scales that preclude effective community-based management with no-take LMMAs. We used acoustic telemetry and tag-returns to examine reproductive migrations and catchment areas of the grouper Epinephelus fuscoguttatus at a spawning aggregation in Papua New Guinea. Protection of the resultant catchment area of approximately 16 km2 using a no-take LMMA is socially untenable here and throughout much of the Pacific region. However, we found that spawning migrations were skewed towards shorter distances. Consequently, expanding the current 0.2 km2 no-take LMMA to 1–2 km2 would protect approximately 30–50% of the spawning population throughout the non-spawning season. Contrasting with current knowledge, our results demonstrate that species with moderate reproductive migrations can be managed at scales congruous with spatially restricted management tools.

Spawning Site Fidelity, Catchment, and Dispersal of Common Snook along the East Coast of Florida

AbstractA population's fidelity to spawning sites and variation in the strength of site fidelity among individuals are influential components of fish population dynamics. The literature on fidelity to aggregation sites is dominated by studies on marine species, whereas less is known about the fidelity of euryhaline species to spawning aggregation sites. We used passive acoustic telemetry to quantify intra‐annual and interannual site fidelity and resident habitat associated with spawning sites (inlets) for 280 sexually mature Common Snook Centropomus undecimalis through an array of more than 200 receivers deployed in rivers, estuaries, inlets, and nearshore waters along 320 km of Florida's Atlantic coast. Fish were detected four times as often at and made twice as many trips to a primary spawning inlet than to secondary inlet sites. Fish displayed interannual site fidelity, returning to the primary inlet for as many as five consecutive reproductive seasons. Overall, individuals returned to their primary inlet (return rate [RR] = 0.54) more often than they changed sites between years (straying rate [SR] = 0.29), but variation in RRs and SRs between inlets suggested a spatial effect on interannual site fidelity. During the nonspawning season, fish generally resided less than 40 km to the northwest of their primary inlet. The 95% kernel density estimates (KDEs) for catchment area and dispersal area averaged 220 km2 and overlapped greatly for five out of six inlets. The 50% KDE did not overlap between inlets, suggesting that each spawning site had a corresponding winter resident habitat supporting a group of fish that were primarily associated with that inlet. The inclusion of telemetry data in traditional measures of site fidelity allowed for the identification and accurate description of behavioral polymorphism and may be applied to other fish species when spatial substructuring is suspected.Received June 9, 2015; accepted December 3, 2015