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An investigation on the feeding and breeding in Bagarius bagarius was examined from Manchar Lake District Jamshoro, Sindh, Pakistan. Total 62 samples were accessed at different length groups during April-September 2022. The range of samples was between (10.0 to 70.0 cm) and from (28-3500 g) in total length and weight respectively. For food determination the experimental fish was divided into three length groups viz., small (10.0-15.0 cm) medium (15.1-30.0 cm) and large (40.0-70.0cm) for the determination of feed preference. The results of the investigations revealed that the food fondness of B. bagarius was detected as highly carnivorous (Piscivorous) displayed higher preferences for fish (46.6 %) seconded by insect larvae (20 %) and 3rd preferred was debris (15.4 %). For breeding analysis values of ova diameter were found to be ranged between 0.55-1.0 mm, the gonadosomatic index (GSI) values were also from to be increasing from 0.71-6.5% and from 0.82-10.28% for both the sexes. These values remained high du ring April to August. It indicated that the fish spawned once in a year in July. Outcomes of egg estimation during the examination depended on 10 matured B. bagarius from Manchar Lake. Fecundity ranged between 260-554 eggs. Least egg estimation 260 was detected from fish of 41.8cm and 88.0 g in length and weight. The highest egg was 554 from 59.0 cm and 155 g in both length and weight. Total body length exhibits better relationship with fecundity of experimental fish B. bagarius from Manchar Lake than the other parameters. [ABSTRACT FROM AUTHOR]

Aspects of the reproductive biology of Atlantic chub mackerel Scomber colias are reported here based on data from random samples of artisanal fish landings from Ghana. The specimens were between 13.7 cm and 40.7 cm total length (TL), and both sexes matured at a mean length (Lm50) of approximately 25 cm TL. An overall sex ratio of 1:1 was estimated for the population. Absolute fecundity of the fish ranged between 10 220 and 155 791 eggs (mean 48 238 [SE 2 324] eggs) in individuals measuring between 22.8 and 36.5 cm TL and weighing 104.3 to 525.3 g. Monthly variations in the gonadosomatic index and the proportion of fish with ripe gonads in the samples indicated the occurrence of spawning activities during two periods, March–April and June–August, the latter period of which coincided with the coastal upwelling season in Ghanaian waters. These findings are compared with those for chub mackerel from the northwestern and southwestern coasts of Africa. The results of this study will help inform the management of this small pelagic species in Ghana. [ABSTRACT FROM AUTHOR]

This present study provides an overview of the reproductive traits, including ovarian development, spawning season, size at maturity (Lm), and fecundity of Acentrogobius viridipunctatus - a high economic value fish in the Vietnamese Mekong Delta (VMD). A total of 432 females were collected using trawl nets from January to December 2020 at four sites, including Long Huu-Tra Vinh (LHTV), Trung Binh-Soc Trang (TBST), Dien Hai-Bac Lieu (DHBL), and Tan Thuan-Ca Mau (TTCM). The ovarian diameter was seen to increase from 2.09 (stage I) to 6.57 mm (stage V). Histological analysis showed that the goby was a multi-spawner due to the different oocyte stages found in stages IV and V of ovaries. It can release eggs all year-round due to the monthly appearance of ovarian stages IV and V during the study period, with the main peak in the 2-4 months of the wet season noted with the highest value of gonadosomatic index at that time. The Lm increased from 6.6 cm at TBST to 9.4 cm at TTCM. This species displayed relatively high fecundity, ranging from 5,481 to 130,683 eggs/female. The average fecundity of this fish was 27,698 ± 7,983 eggs/female at LHTV, 46,592 ± 7,264 eggs/female at TBST, 23,271 ± 4,985 eggs/female at DHBL, and 31,408 ± 2,515 eggs/female at TTCM. Egg diameter ranged from 0.45 ± 0.01 at DHBL to 0.50 ± 0.01 at TBST. For sustainable exploitation, local governments should ask the fishers to avoid catching fish during the main spawning period, and the fish length at first capture should be >Lm. [ABSTRACT FROM AUTHOR]

The ovarian development, spawning pattern and season, size at first maturity and fecundity of Glossogobius sparsipapillus, which is an essential commercial fish in the Mekong Delta, have been studied. Totally, 317 fish were collected from the estuarine and the coastal regions including Vinh Hau, Hoa Binh to Dien Hai, Dong Hai (Bac Lieu Province) and Tan Thuan, Dam Doi (Ca Mau Province). Fishes were sampled using gill nets during the dry and wet seasons in April 2019 - January 2020. The results show that the ovaries have different types of oocytes and that this goby was a multiple spawner. It spawned from July to September at three of the studied sites, since most of the mature ovaries appeared at that time. The size at first maturity (Lm) was from 6.50 cm in Vinh Hau and Tan Thuan to 6.78 cm in Dien Hai. The average batch fecundity was 24,966±2,542 eggs, ranging from 17,918±2,258 SE in Vinh Hau to 28,700±5,322 SE in Dien Hai, followed closely by Tan Thuan (26,352±3,458 SE). There was an increase in batch fecundity with fish size. The fish total length and weight had strong positive relationships with batch fecundity. The egg size was 48.20±4.89 SE µm length and 26.39±3.09 SE µm width. [ABSTRACT FROM AUTHOR]

Intra-and interannual variability of fecundity and egg size of lumpfish (Cyclopterus lumpus) were assessed for 2009 and for 2014-2019 and compared with fecundity estimates from 1967 and 1969. Downregulation of fecundity was apparent throughout ovary development, but the intensity was reduced close to spawning. The fecundity of fish spawning later in the year was higher than that of fish that spawned earlier. Carcass weight was a better predictor of fecundity than length. The model was improved through the addition of liver weight, but this led to an increase of <1.0% in the explained variance in fecundity. Variation in fecundity between the periods studied (2009 and 2014-2019) was low; however, fecundity in these study periods was higher than in 1967 and lower than in 1969. Whether these differences were due to differences in methods could not be ruled out. Average egg diameter was positively correlated with fish size and decreased from the first to the second batch, and only limited variation between years was observed in this characteristic. [ABSTRACT FROM AUTHOR]

The recruitment of primary growth (PG) oocytes to the secondary growth (SG) phase within the ovulatory cycle, i.e. time interval between two sequential ovulation/spawning events, has rarely been examined in detail in a quantitative manner for batch spawning fishes with indeterminate fecundity. In the present study we analyzed the ovarian dynamics of Macedonian shad, Alosa macedonica , an iteroparous batch spawning clupeid with indeterminate fecundity, with the main goal to define the timing of PG recruitment and relate it to the ovulatory cycle. The latter was classified into four different phases (pre-ovulatory, running, post-ovulatory, intermediate) through postovulatory follicles and presence/absence of hydrated oocytes. Various indices of ovarian dynamics, including the formation and mean diameter of the advanced oocyte batch, the ovarian developmental stage, the oocyte size modality and the gonadosomatic index, varied among the ovulatory phases, evidencing cyclicity. Relative fecundity of newly recruited SG oocytes was used as an index of PG recruitment intensity and was shown to follow a specific pattern within the ovulatory cycle; PG recruitment occurred in a stepwise manner and in parallel with ovulation of the advanced oocyte batch, and synchronization of these two processes kept the ovary in a state of dynamic equilibrium. • The process of oocyte recruitment has rarely been examined in detail in a quantitative manner within the spawning cycle. • Oocyte recruitment occurred in a stepwise manner within the spawning cycle in an indeterminate batch spawning fish. • Spawning of the advanced batch and oocyte recruitment were synchronized, keeping the ovary in a state of dynamic equilibrium. [ABSTRACT FROM AUTHOR]

The reproductive characteristics of Gymnocypris firmispinatus were determined from 582 individuals collected in the Anning River, China. The sex ratio (male: female) was 1:1 for the overall population but 3.1:1 for the mature group. Females reached a larger total length and total weight (242 mm and 148.17 g) than males (163 mm and 41.58 g). Lengths and ages at maturity were estimated to be 83.4 mm and 2.4 years for males, 130.7 mm and 5.9 years for females, respectively. Based on the analyses of gonad development and the size distribution of oocytes, G. firmispinatus spawned from March to May with high degree of the spawning synchronicity. The opposite tendency between gonado-somatic index and hepato-somatic index from January to March in females indicated that the energy requirement for the oocytes growth may be derived from the liver. In addition, the estimated mean fecundity and mean relative fecundity were 1227 and 29.7 eggs per g total weight. The fecundity of G. firmispinatus increased linearly with increasing of total length, total weight and ovary weight. This study provides details about the reproduction suggesting that G. firmispinatus might be especially vulnerable to exploitation in the Anning River. [ABSTRACT FROM AUTHOR]

The daubed shanny Leptoclinus maculatus is a relatively common fish species in Svalbard waters, but little is known about its reproduction. In total, 207 specimens (76 females, 131 males) were collected and examined. Gonadosomatic (GSI) and hepatosomatic indices were significantly higher in females (mean 2.8 and 2.7%, respectively) than males (mean 0.3 and 1.8%) in all seasons. The GSI of females was highest during autumn and winter (18.5%) while the GSI of males was highest in winter (1.7%). Females become sexually mature at 125 mm standard length (SL) and 7 years of age while males become sexually mature at similar length and 6 years of age. The number of oocytes in gonads increased with SL and age and comprised two groups: (1) 115-124 mm SL, 5-7 g gutted weight (GW) and 5-6 years of age with potential fecundity of 950-1850 oocytes, (2) 125-134 mm SL, 7-9 g GW and 7-12 years of age with 1250-2800 oocytes. The daubed shanny seems to spawn all its ripe oocytes during one spawning event each year. Fish become sexually dimorphic after maturation, and differences in sexual morphology are likely linked to reproduction, with female parental care and territorial defence for males. The reproductive strategy of daubed shanny is characterized by late maturation, relatively low fecundity and large size of offspring, i.e. large investment in relatively few offspring. [ABSTRACT FROM AUTHOR]

Abstract: A mismatch in synchrony between male and female gamete release in external fertilizers can result in reduced or failed fertilization, sperm competition, and reduced paternity. In Arctic charr (Salvelinus alpinus), males can adopt either a guard or sneak tactic resulting in both pre‐ and postcopulatory competition between males with alternative reproduction tactics. Here, spawning behavior of free‐living Arctic charr was video‐recorded, and their reproductive behavior was analyzed. From evaluating 157 spawning events, we observed that females mainly spawned with a guarding male and that the female and the guarding male synchronized timing of gamete release under sperm competition. Although sneakers spawned with higher synchrony than the guarding male in single‐male spawning events, the average sneaker released his milt less synchronized with the female than the guarding male under sperm competition. Approximately 50% of the recorded spawning events occurred under sperm competition, where each event included an average of 2.7 males. Additionally, sneakers were more exposed to sperm competition than guarding males. An influx of males, in close proximity to the female, occurred during the behavioral sequences leading up to egg release, but this influx seemed not dependent on egg release, suggesting that something else than gonadal product attracts sneaker males to the spawning female. Just before and during the actual release of gametes, the spawning couple vibrates their bodies in close contact and it seems likely that this vibrational communication between the spawning couple, which results in a larger amplitude sound wave than seen under regular courting, reveals time of gamete release to sneaker males. Thus, vibrational communication may enable synchrony between the guarding male and the female, and this might be traded against the cost of higher detectability from surrounding sneaker males, eavesdropping in close proximity. [ABSTRACT FROM AUTHOR]

Wild haddock ( Melanogrammus aeglefinus ) of commercial size (0.8–2.49 kg, 45–60 cm) were swum to exhaustion in a large swim tunnel and then allowed to recuperate for 0, 3 or 6 h, to investigate the effects of exhaustive swimming on blood glucose, blood lactate and post mortem development of fillet quality. There was a positive linear relationship between critical (aerobic) swimming speed (U crit ) and body length (BL). The average U crit was 1.25 ± 0.29 (SD) BL s −1 , which is close to that reported by others for haddock. Swimming to exhaustion resulted in reduced time to reach maximum muscle stiffness of the fillet (no recuperation vs unswum control), but the effect was remedied by recuperation for 3 h or more. Blood glucose and blood lactate increased during exercise and remained elevated throughout the entire 6-h resting period, indicating that complete recovery of these parameters may take more than 6 h. There was no significant effect of exhaustive swimming on muscle pH or colouration of the fillet. Taken together, the data suggest that swimming to exhaustion may have moderate and reversible negative effects on fillet quality in haddock. The effects observed in the present study are consistent with a recent study on exhaustive swimming in Atlantic cod, but less severe than that reported for haddock caught by trawl. This suggests that other factors (e.g. crowding/packing in the codend, barotrauma or suffocation) are contributing to the deterioration of fillet quality seen frequently in haddock caught by trawl. [ABSTRACT FROM AUTHOR]

This study describes the spawning of the fatheads Psychrolutes marmoratus and Cottunculus granulosus, two psychrolutid species that inhabit the shelf edge and continental slope of the south-west Atlantic. Females lay large eggs of c. 2·5 mm ( P. marmoratus) and 4·5-5·0 mm ( C. granulosus); fecundity is from the hundreds ( C. granulosus) to a few thousand eggs ( P. marmoratus). Egg maturation is synchronous in P. marmoratus with an autumn-winter peak of spawning and group-synchronous in C. granulosus, which reproduces all year round. In the fishery, females predominate among adult fish in both species, possibly indicating male nest guarding on hard grounds inaccessible to fishing vessels. The reproductive strategy of representatives of the Psychrolutidae is similar to that of other sculpins of the superfamily Cottoidea. [ABSTRACT FROM AUTHOR]

The spawning characteristics of round herring Etrumeus teres remain unclear despite its commercial and ecological importance. The oocyte growth and maturation during the spawning cycle of round herring were examined based on the samples collected at different hours of the day off southern Japan during their 2015 spawning season. The ovarian histological analysis showed that germinal vesicle migration (GVM) and subsequent germinal vesicle breakdown occurred from the afternoon to the next morning. The appearance of hydrated oocytes indicated that round herring spawned between midday and evening. Degeneration of post-ovulatory follicles and the ovarian developmental stage suggested that individual round herring did not spawn on consecutive days but rather spawned at an interval of at least 2 days. The oocyte diameters of the second clutch (subsequent spawning batch) increased gradually when the first clutch (spawning batch) underwent GVM and hydrated, but oocytes in the second clutch increased significantly in size immediately after spawning, suggesting that vitellogenesis of the second clutch may be accelerated for the next spawning. Size at maturity in all females was estimated to 17.6 cm in body length (BL), and batch fecundity was 1409–21,023 oocytes (15.7–24.0 cm in BL). Our findings provide a foundation for conducting stock assessment studies on round herring using an egg production method. [ABSTRACT FROM AUTHOR]

A recent meta-analysis by Barneche et al. (2018; Science, 360(6389): 642–645) shows that fish reproductive output scales hypergeometrically with female weight. This result challenges the common assumption that reproductive output is proportional to weight. The implication made is that current theory and practice severely underestimate the importance of larger females for population replenishment. Their example for cod (Gadus morhua) shows that current practice makes an error of 149%. By properly accounting for fish demography, we show that the error is maximally on the order of 10% and in most other fish stocks likely much less. [ABSTRACT FROM AUTHOR]

Wild caught North Sea saithe Pollachius virens were monitored for growth, sex steroid profiles and oocyte development pre-spawning and measured for egg size and group fecundity during the spawning season in the laboratory. Vitellogenesis commenced in late October-early November, at a leading cohort size ( CL) of c. 250 µm, after which oocytes grew rapidly in size until spawning started in February. Notably, a distinct cortical alveoli stage was virtually absent with yolk granules observed in developing oocytes at the very beginning of vitellogenesis. Little atresia was observed pre-spawning, but atretic re-absorption of remnant oocytes containing yolk granules was found in all females immediately post-spawning. As expected, concentrations of sex steroids, oestradiol-17β (females), testosterone (both sexes) and 11-ketotestosterone (both sexes), increased pre-spawning before dropping post-spawning. The present experiment provides the first validation of sex steroid levels in P. virens. Post-ovulatory follicles were visible in histological sections from female gonads 9-11 months post-spawning, but then disappeared. Spawning commenced around a CL of c. 750 µm (700-800 µm). Hydrated oocytes (eggs) measured between 1·04 and 1·31 mm (mean = 1·18 mm) with decreasing sizes towards the end of spawning. The average estimated realized fecundity was c. 0·84 million eggs (median female total length, LT = 60 cm). Spawning lasted from 13 February to 29 March. [ABSTRACT FROM AUTHOR]

Simultaneous hermaphrodites that exchange gametes within pairs allow us to test whether equity of resource exchange is positively associated with duration of cooperative partnerships. The chalk bass (Serranus tortugarum) provides an excellent model system for such research because they spawn daily, trading sex roles with the same mating partners in repeated spawning bouts (a tactic called "egg parceling"). Even so, they live in site-attached aggregations with opportunities for extra-pair matings. We asked whether individuals spawn preferentially with 1 long-term partner and whether partner fidelity was associated with matching in the number of eggs produced in a single day by individuals within pairs. In addition, we observed random focal individuals during spawning to determine whether egg parceling was coordinated within pairs: we asked whether parcel number (per day) was well matched within pairs and whether parcels were exchanged in nonrandom sequences. We did not witness any "break-ups" in our long-term pairs; during each monthly census, all identified pairs were found spawning and courting with their "primary" mating partner until one or both of them disappeared. Daily egg production and the number of egg parcels exchanged within primary partnerships were coordinated. The sequence of parcel exchange was fairly regular, although ca. 20% of focal individuals fertilized or exchanged a few egg parcels with another partner(s); parceling allows individuals the option to exchange eggs outside of the primary pair. Our study provides novel empirical evidence of strong pair bonds and resource matching even in relatively large social groups with extra-pair trading opportunities. [ABSTRACT FROM AUTHOR]

The goby Parapocryptes serperaster is a bottom dweller fish widely distributed in monsoonal regions in Asia, but its reproductive biology is poorly understood. This study assessed important variables associated with P. serperaster reproduction through monthly field collection and histological analysis in the Mekong Delta, Vietnam over a year. This goby species is a multiple spawner as the ovaries contained oocytes at different developmental stages during the spawning season, coinciding with the spawning period in the wet season. Peak spawning occurred in September when the gonadosomatic index was close to the highest value. This goby shows sexual dimorphism in body size, and the average size at first sex maturation was 15.8 cm total length in the female and 16.3 cm in the male. Fish reproduction was characterised by high variation of fecundity and heterogeneous size of eggs in the ovary, indicating a possible adaptation to the monsoonal region. This study provides new understanding on the spawning pattern and reproductive biology of P. serperaster living in the mud flat habitat in tropical monsoon climate. [ABSTRACT FROM AUTHOR]

Jack mackerel ( Trachurus declivis ) is a key target species of the Australian Small Pelagic Fishery. The fishery was subject to extensive public scrutiny following an attempt to introduce a large factory-trawler in 2012. One of the concerns raised related to the reliability and age of estimates of the spawning biomass of jack mackerel. This study reports on the first dedicated application of the Daily Egg Production Method (DEPM) to jack mackerel. Large numbers of samples of eggs and adults were collected concurrently from the key spawning area off eastern Australia during what has been previously identified as the main spawning period. This study established an effective adult sampling method and provides the first estimates for this species of adult reproductive parameters required for application of the DEPM. Estimates of all DEPM parameters, except batch fecundity, were based on relatively large sample sizes. The spawning biomass of jack mackerel off eastern Australia during January 2014 was estimated to be approximately 157,805 t (95% CI = 59,570–358,731 t). Sensitivity analyses indicate this estimate is robust to likely uncertainty in estimates of key parameters. Future research should focus on elucidating the size-fecundity relationship and spatial, temporal and size-related variations in spawning fraction. [ABSTRACT FROM AUTHOR]

This is the first report on the fecundity in adults of two nonparasitic lamprey species at risk, the Vulnerable Kern Brook Lamprey, Lampetra hubbsi and the Critically Endangered Macedonia Brook Lamprey, Eudontomyzon hellenicus. The mean absolute fecundity of L. hubbsi was 1865 eggs and that of E. hellenicus was 994. The higher fecundity in L. hubbsi was directly related to its higher mean gonadal mass (0.90 g) relative to that in E. hellenicus (0.52 g). Based on preserved museum material possessing well-developed primary and secondary sexual characters, the spawning period for L. hubbsi was inferred to be February-March and for E. hellenicus to either extend from January to May or to occur as separate events; one in January and the other in May. Because metamorphosing ammocoetes of E. hellenicus have been collected in October and in January, it is hypothesized that those metamorphosing in October spawn in January and those metamorphosing in January spawn in May. These periods need to be corroborated with field observations. Evidence for E. hellenicus spawning in January is based on the presence of spent females of this species collected in that month. [ABSTRACT FROM AUTHOR]

To illustrate the spawning characteristics of skipjack tuna Katsuwonus pelamis in the Northwestern Pacific Ocean, we examined seasonal changes in the histological condition of gonads, spawning fraction, and batch fecundity (BF) of skipjack tuna caught around Amami-Oshima in the northern Nansei Islands, Japan, from May 2011 to July 2013. Females classified as 'mature' appeared from June to October, and mature males were present from April to November. Spawning began in June when the sea surface temperature (SST) exceeded 24 °C and peaked in August. Although the SST was still above 24 °C, spawning ended in September when the SST started decreasing continuously. The minimum size (fork length, FL) at first maturity was 40.5 cm for females and 37.6 cm for males. The BF (mean ± SD) and relative batch fecundity (RBF) were estimated at 93,700 ± 21,800 oocytes and 56.8 ± 14.3 oocytes/g, respectively. The total spawning fraction (spawning intervals) during the spawning season was estimated at 0.53 (1.88 days). These results indicate that the spawning activity of skipjack tuna around Amami-Oshima changes seasonally depending on SST. [ABSTRACT FROM AUTHOR]

A previous study using two commercial pelleted diets (broodstock and on-growing diets) and a baitfish diet to feed hatchery-reared Atlantic cod ( Gadus morhua) broodstock revealed higher growth and size of spawners as well as higher fertilization and hatch success in the group fed the baitfish diet, but no differences in egg diameter or blastomere normality. In the present study, we explore differences in condition and growth of cod larvae to assess the effect of the abovementioned broodstock diets on offspring using protein-specific growth rates and RNA/DNA ratios (RNA/DNA). Changes in RNA/DNA with time (after 7 days post-hatch) were significantly lower in the broodstock diet group compared with the other two groups, suggesting a lower feeding condition and growth potential. However, our results show no differences in growth and survival up to 49 dph between the larvae originating from broodstock fed the three diets. Contrary to other authors' findings, we found no correlation between the RNA/DNA and instantaneous growth rates possibly due to the variability in growth observed within diet groups. Our results provide information about the effects of broodstock diets on early larval growth and survival of Atlantic cod. [ABSTRACT FROM AUTHOR]

In order to illustrate the reproductive activity of Pacific bluefin tuna ( Thunnus orientalis) around the Yaeyama archipelago, an area known to be the species' major spawning ground, gonadal condition of large individuals obtained by longline fishing was assessed during the commercial fishery season between late April and early July in 2008 and 2009. Almost all of the specimens landed at Ishigaki Island during these two seasons were larger than 200 cm in fork length (FL), and, while the sex ratio was nearly 1:1 in total, a significant bias existed towards males when only individuals with FL values greater than 230 cm were considered. All females were sexually mature and sperm was observed in the testes of all males throughout the fishing season. Average spawning intervals (fraction) and average batch fecundity (mean ± SD) were estimated at 3.29 days (0.30) and 15.4 ± 10.2 million oocytes, respectively. Ovarian and testicular maturation phase based on histological assessment did not show any significant changes over the two-year study period, while commencement of spawning varied from year to year. We determined that spawning activity of Pacific bluefin tuna around the Yaeyama archipelago persisted throughout the fishing season, and likely varied due to the annual fluctuations in environmental conditions at the spawning ground. [ABSTRACT FROM AUTHOR]

The fecundity type (determinate vs. indeterminate) is still uncertain for many commercially important fish populations affecting accuracy in fecundity estimations and hindering the selection of appropriate egg production methods for stock assessment purposes. It is broadly considered that boreal fish populations living in colder habitats are determinate spawners whilst populations residing in warmer habitats tend to be indeterminate spawners. In the present study we modelled the determinate–indeterminate fecundity type in batch spawning fishes, i.e. fish that spawn several batches of eggs per spawning season, based on the relationship between oocyte growth period and the duration of the spawning period considering that both variables can be affected by water temperature and latitudinal distributions. Individual based models (IBMs) were developed to explore how the interaction of these variables can result in a series of patterns along the continuum from extreme determinacy, i.e. annual fecundity being recruited long before the onset of the spawning period, to indeterminacy. Model simulations showed that fish stocks with oocyte growth periods longer than the spawning period are predicted to exhibit determinate fecundity which provides a fair justification for why cold water species with slow oocyte growth and limited spawning periods are determinate spawners and vice versa. [ABSTRACT FROM AUTHOR]

Abstract: Growth information is important for stock assessments because it gives an indication of spawning stock biomass in the form of weight or fecundity, which is an important indicator of stock status, as well as being important if fitting to length composition data. Sampling for growth characteristics should include all ages and sizes in the population, but data are often only available from fishery-dependent sampling, which can lead to biased estimates of true underlying population growth parameters because of selectivity, which includes both gear selectivity and availability. Two stock assessments with the potential for biased growth because of dome-shaped selectivity and lack of fishery-independent age data are the Gulf and Atlantic menhaden assessments. The objectives of our study were (1) to develop and test a method to estimate unbiased growth parameters regardless of the selectivity of the gear used to sample ages and lengths and (2) to apply the proposed method to fit unbiased population growth parameters for Gulf and Atlantic menhaden. We propose a method to adjust for the bias in the growth curve parameters and account for missing samples at smaller and larger lengths. The proposed method was tested on simulated data and applied to data for Gulf and Atlantic menhaden. Use of the adjustments was robust and resulted in reduced bias in the growth parameter estimates with accuracy being affected by both sample size and variability in mean length at age. Increasing the sample sizes increased the accuracy of the adjustments (i.e., as the coefficient of variation (CV) for length at age increased, the accuracy of the estimates decreased). For Gulf menhaden, the parameters estimated for the unadjusted growth curve were L ∞ =240.8, k =0.38, t 0 =−1.14, and CV of length at age=0.06 (assumed constant) with a total sample size of 366,710 from 1977 to 2011. For Atlantic menhaden, the parameters estimated for the unadjusted growth curve were L ∞ =350.9, k =0.32, t 0 =−0.83, and CV of length at age=0.12 (assumed constant) with a total sample size of 480,668 from 1955 to 2011. The adjustment for a maximum length of capture had a large impact on the overall growth parameters for both species, while the adjustment for a minimum length of capture had less impact. Bias in the growth curve parameter estimates can be reduced by using the method outlined to account for selectivity. [Copyright &y& Elsevier]

Historical fecundity estimates of American ShadAlosa sapidissimaused a determinate method that estimated annual fecundity as the standing stock of oocytes at a single point of time prior to spawning. Such fecundity estimates have been (1) reported for populations from the Canadian Maritimes to Florida, (2) applied to hypothesis tests of life history evolution, and (3) used in demographic models to advise management policy. However, American Shad have asynchronous development of yolked oocyte clutches, which suggests that new oocytes could arise after spawning commences, biasing the results of a determinate fecundity method downward. If so, annual fecundity should be a product of batch size and the number of batches—an indeterminate fecundity method. We investigated oocyte recruitment, atresia, and spawning intervals using gonad histology of females from the Mattaponi River, Virginia. Batch size (i.e., the number of hydrated oocytes prior to a spawning event) was estimated using a gravimetric method. Spawning duration was obtained from an independent acoustic tagging study. A size hiatus between primary and secondary oocytes was only evident in some individuals during spawning, so we conclude that an indeterminate fecundity method is necessary for this population of American Shad. Atresia was evident during spawning but was low at the end of the 2002 spawning season. Females spawned every 2.2–2.9 d, releasing 11–17 batches per season. Batch fecundity (range: 12,700–81,400) was 23% higher for repeat versus virgin spawners. A bootstrapped estimate of potential annual fecundity for a virgin female—as calculated with an indeterminate fecundity method—was 478,000–544,000 eggs (95% confidence interval), about double the previous (determinate) estimates from this river system (260,000 and 288,000). Until more comparisons are done with other populations, we urge caution in using the many published determinate fecundity estimates of American Shad and otherAlosaspecies. Received June 3, 2013; accepted October 25, 2013 [ABSTRACT FROM AUTHOR]

We collected data on the distribution, sex, size, fecundity, and food habits of a newly discovered population of Misgurnus anguillicaudatus (Oriental Weatherfish) in the Hudson Valley, NY. Oriental Weatherfish were distributed throughout the Dwaar Kill in Orange and Ulster counties and at least 7 km of the Wallkill River, principally in the soft substrates of stream margins. Males were smaller than females and apparently had shorter life spans. Sexual maturity and spawning attributes were evident. Mature males had pronounced dorsolateral ridges on at least the posterior third of the body, and females exhibited post-spawning abrasions dorsal and anterior to the vent. Female Oriental Weatherfish are batch-spawners producing up to 18,000 eggs at one time. Oriental Weatherfish in the Dwaar Kill consumed a variety of aquatic macroinvertebrates and exhibited generalist feeding habits. This species does not seem to be affecting other vertebrates where currently found, but potential negative interactions with the native Umbra pygmaea (Eastern Mudminnow) merit attention. Monitoring of the Hudson Valley populations is needed to determine if Oriental Weatherfish abundance or range changes dramatically, and to determine if their presence is causing any lasting effects on the ecosystem. [ABSTRACT FROM AUTHOR]

Ovaries of 1159 Trachinocephalus myops were examined, and six oocyte stages were histologically identified whereby each stage of ovary development was observed almost every month. The sex ratio was not different from 1 : 1 (P > 0.01). The weight-length relationship was estimated as BW = 0.0077FL3.1207 (r2 = 0.976, n = 2256). Monthly composition of the oocyte stages gonadosomatic index ( GSI), and condition factor ( CF) were examined. The spawning season had two peaks: February to April and August to October. Sizes at 50% maturity were estimated at 18.0 and 18.7 cm FL for females and males, respectively. Fecundity estimates ranged from 11 100 to 426 200 (mean: 178 600), based on an oocyte diameter >0.2 mm. Batch fecundity was estimated to range from 1724 to 120 951 (mean: 60 200), germinal vesicle migration and mature oocytes >0.8 mm in diameter were counted, and the relative fecundity was estimated to range from 346 to 3115 (mean: 1087). The results suggest that reproductive activity occurred throughout the year, suitable for the highly variable environments utilized by this species. [ABSTRACT FROM AUTHOR]

Some aspects of the reproductive biology of Sepia orbignyana, such as fecundity, spawning strategies, and gonad histology, have been studied in 1048 specimens (538 males and 510 females) caught during trawl surveys from May 2008 to April 2009 in the Aegean Sea. The length at 50% maturity was estimated as 50 mm for males and 70 mm for females. The smallest mature female had a mantle length (ML) of 36 mm; the smallest mature male had a 32-mm ML. The total egg counts (potential fecundity) in females of 60-84 mm in ML varied between 201 and 1532. The spermatophore counts in mature males (ML = 42-67 mm) were between 68-1055, with a mean of 485. [ABSTRACT FROM AUTHOR]

Knowledge on the reproductive biology of fishes is critical for understanding a species' life history and devising appropriate management strategies. Anthropogenic forces, such as damming and overfishing, threaten fishes endemic to the upper Yangtze River. We conducted a study on the reproductive biology of an endemic species, Ancherythroculter nigrocauda in order to provide information on the life history of this species and to assist in its conservation. From July 2011 to June 2012, a total of 417 fishes were captured via monthly sampling by fishermen in the Longxi River, a tributary in the upper Yangtze River. Although the female-male ratio was 1:1.03, females were predominantly larger in body size. Gonad somatic indices and oocyte diameter distribution showed that the spawning period of A. nigrocauda in the Longxi River ranged from April to August, with the peak in April. Body length at 50 % sexual maturity of A. nigrocauda was estimated to be 125 and 106 mm for females and males, respectively. Absolute fecundity of A. nigrocauda varied between 11,300 and 504,630 eggs, with the mean of 162,377 eggs. In conclusion, A. nigrocauda mature early, spawn once, and are highly fecund, all of which are consistent with an r-selected life history. It is recommended that a moratorium on fishing this species be enacted and the culture of this species be continued. [ABSTRACT FROM AUTHOR]

Broadcast spawning invertebrates that live in shallow, high-energy coastal habitats are subjected to oscillatory water motion that creates unsteady flow fields above the surface of animals. The frequency of the oscillatory fluctuations is driven by the wave period, which will influence the stability of local flow structures and may affect fertilization processes. Using an oscillatory water tunnel, we quantified the percentage of eggs fertilized on or near spawning green sea urchins, Strongylocentrotus droebachiensis. Eggs were sampled in the water column, wake eddy, substratum and aboral surface under a range of different periods (T = 4.5 – 12.7 s) and velocities of oscillatory flow. The root-mean-square wave velocity (rms(uw)) was a good predictor of fertilization in oscillatory flow, although the root-mean-square of total velocity (rms(u)), which incorporates all the components of flow (current, wave and turbulence), also provided significant predictions. The percentage of eggs fertilized varied between 50 – 85% at low flows (rms(uw) <0.02 m s−1), depending on the location sampled, but declined to below 10% for most locations at higher rms(uw). The water column was an important location for fertilization with a relative contribution greater than that of the aboral surface, especially at medium and high rms(uw) categories. We conclude that gametes can be successfully fertilized on or near the parent under a range of oscillatory flow conditions. [ABSTRACT FROM AUTHOR]

The spawning behavior of captive Bluefin Tuna (Thunnus thynnus) was observed in cages at an Adriatic facility in summer 2011. Approximately 20,000 eggs were collected from cages and transferred to a land-based nursery, with an estimated fertilization success rate of 80%. Eggs were spherical with a diameter of 1,035.06 ± 20.16 μm and were pelagic with a single oil globule (227.63 ± 8.07 μm). Newly hatched larvae (3.08 ± 0.14 mm total length) followed scombrid larval development: melanophores were scattered over the body, head, notochord, and yolk, except finfold; eye pigmentation was observed 1.5 days posthatch, pectoral fins started to appear, and two-thirds of the yolk sac were absorbed; the mouth developed at 2.5 days posthatch, and larvae began feeding upon enriched rotifers. After mortalities occurred in the nursery (5 days posthatch), DNA was extracted from a sample of larvae. An 890 base pair fragment of the mitochondrial partial control region was amplified and sequenced to genetically confirm fish species identity. Based on multiple sequence alignment, larval sequences showed no ambiguities to the T. thynnus mitochondrial control region, thereby confirming spontaneous spawning in captivity. Although such an event has previously been reported in the Mediterranean, this is the first report supported by both morphological and genetic data. [ABSTRACT FROM AUTHOR]

Broadcast spawning invertebrates that live in shallow, high-energy coastal habitats are subjected to oscillatory water motion that creates unsteady flow fields above the surface of animals. The frequency of the oscillatory fluctuations is driven by the wave period, which will influence the stability of local flow structures and may affect fertilization processes. Using an oscillatory water tunnel, we quantified the percentage of eggs fertilized on or near spawning green sea urchins, Strongylocentrotus droebachiensis. Eggs were sampled in the water column, wake eddy, substratum and aboral surface under a range of different periods (T = 4.5 – 12.7 s) and velocities of oscillatory flow. The root-mean-square wave velocity (rms(uw)) was a good predictor of fertilization in oscillatory flow, although the root-mean-square of total velocity (rms(u)), which incorporates all the components of flow (current, wave and turbulence), also provided significant predictions. The percentage of eggs fertilized varied between 50 – 85% at low flows (rms(uw) <0.02 m s−1), depending on the location sampled, but declined to below 10% for most locations at higher rms(uw). The water column was an important location for fertilization with a relative contribution greater than that of the aboral surface, especially at medium and high rms(uw) categories. We conclude that gametes can be successfully fertilized on or near the parent under a range of oscillatory flow conditions. [ABSTRACT FROM AUTHOR]

Abstract: Understanding the relationship between abundance of spawners and subsequent recruitment is one of the central issues in fisheries stock assessment. We developed a new, pre-recruit survival based stock–recruitment model that enables explicit modeling of survival between embryos and age 0 recruits, and allows the description of a wide range of pre-recruit survival curves. The model is especially useful for low fecundity species that produce relatively few offspring per litter and exhibit a more direct connection between spawning output and recruitment than species generating millions of eggs. The proposed model provides additional flexibility in the stock–recruitment options that may be explored in any fishery stock assessment, and it is now available within the Stock Synthesis assessment platform. In this paper, we describe the mathematical formulation of the new stock–recruitment model, explain how this model can be specified within Stock Synthesis, and use it to model the stock–recruitment relationship of the spiny dogfish shark in the Northeast Pacific Ocean. We compare the results of the application of our new stock–recruitment model, with those from traditional Beverton–Holt relationship, and illustrate why the new approach is more appropriate for this species. [Copyright &y& Elsevier]

Theoretical models predict that increased mate availability accelerates filial cannibalism by the parental male, but we do not yet fully understand how the various aspects of mate availability contribute to this effect. We examined the effects of two elements of mate availability-female fecundity and sex ratio-on filial cannibalism by the lizard goby, Rhinogobius flumineus, which is a paternal nest brooding fish. We used three types of females (stimulus-females): a single female with slim belly (not ready to spawn), a single gravid female (ready to spawn), and two gravid females. Stimulus-females were housed in a transparent cage and shown to subject males just before and after spawning with a separate female, after which males cared for the brood. A single gravid stimulus-female accelerated filial cannibalism, compared with a control-stimulus consisting of an empty cage, but only during the early care period. In contrast, a single slim-bellied stimulus-female did not accelerate cannibalism. A stimulus of two gravid females accelerated cannibalism to the same degree as a single gravid female stimulus. Our results suggest that in lizard gobies, filial cannibalism by parental males is accelerated by female quality (fecundity) in the early care period, but not by a higher number of available females (sex ratio). [ABSTRACT FROM AUTHOR]

Abstract: Marine fish populations may exhibit a number of complexities in their reproductive dynamics, such as weight-specific relative fecundity (i.e. eggs produced per spawner weight increases with spawner size) and maternal effects (i.e. reduced larval survival with reduced spawner age), that are typically not incorporated in stock assessment models. Improved information on reproductive biology could alter estimates of stock productivity and potentially improve estimation of stock–recruitment parameters. In this study, we examined the influence of maternal effects and weight-specific relative fecundity on stock status (defined as reproductive potential and measured as eggs, larvae, or spawning stock biomass), F msy, and the statistical fit of stock–recruitment curves estimated within the Bering Sea/Aleutian Islands Pacific ocean perch (Sebastes alutus) and Gulf of Alaska walleye pollock (Theragra chalcogramma) statistical catch-at-age assessment models. In each example, estimates of recruitment strength and the variation around stock–recruitment curves were relatively insensitive to various indices of reproductive potential. However, weight-specific relative fecundity increased estimates of F msy, whereas maternal effects decreased estimates of F msy. The range of F msy estimates obtained for walleye pollock from eight indices of reproductive potential was 0.12–0.19, whereas the F msy range for Pacific ocean perch from three indices of reproductive potential was 0.079–0.084. For walleye pollock, weight-specific relative fecundity and recent increases in spawner weight-at-age resulted in an upward trend in reproductive potential relative to constant relative fecundity with spawner size. The two examples demonstrate the influence of reproductive biology upon stock productivity even in cases where residual recruitment variation is relatively unaffected, and motivate the ongoing monitoring of reproductive status and its incorporation in estimation of fishing rate reference points. [Copyright &y& Elsevier]

Abstract: The Northeast Arctic (NEA) haddock (Melanogrammus aeglefinus) population size has fluctuated greatly over the last few decades. Such fluctuations may be influenced by changes in reproductive investment, yet no fecundity study on this population has been undertaken since 1974 with which to address such a concept. We therefore estimated potential fecundity of >350 NEA haddock caught in February–March 2009–2011 and correlated this with potential fecundity proxies, i.e. female age, length, relative liver size and somatic condition and leading oocyte cohort development (diameter) (LC 20). We also examined the incidence (prevalence) and intensity of atresia in histological ovary sections. Finally, we estimated population (total) egg production (TEP) for NEA haddock in 2010 and 2011. Fecundity was mainly determined by length, although it was also positively associated with our metric of liver size and somatic condition. Fecundity decreased with LC 20, indicating atresia, confirmed by the direct observation of atresia in histological sections (n =185). Although 45% of the females possessed atretic oocytes, the intensity of atresia was low, typically only 1–5% of the oocytes with yolk granules were atretic, complete reabsorption of all vitellogenic oocytes was not observed. Our proxies give no indication of any change in reproductive investment for NEA haddock in the last few decades. The present study confirms the importance of liver and white muscle energy for oocyte recruitment and shows atretic down-regulation in NEA haddock. Further, NEA haddock females whose oocytes reach the yolk granule stage will likely spawn. NEA haddock TEP for females aged 4–8 years was estimated to be 4.5×1013 and 2.9×1013 in 2010 and 2011, respectively. [Copyright &y& Elsevier]

Abstract: The following two hypotheses, using several years of data collected for Barents Sea and Irish Sea cod (Gadus morhua), are scrutinized: (1) potential fecundity closely reflects realised fecundity, and (2) that realised fecundity or associated properties such as spawning duration or egg weight are not dependent on maternal size or condition. Pre-spawning relative fecundity was dependent on stock, fish length and declined by 27 and 30% in Barents Sea and Irish Sea cod, respectively, due to atresia during maturation from 500 to 750μm mean follicle diameter. A further decline of 4% in the relative fecundity was found in Barents Sea cod when their relative condition was low. No significant change in the standard deviation of follicle diameter during maturation from 500 to 750μm could be demonstrated, but fish length and condition were positively correlated. We consider that the standard deviation of vitellogenic follicles moderates an individual fish''s spawning duration following experiments with captive Barents Sea cod where spawning duration increased with fish length (5 and 11days in 52.5 and 96cm females, respectively at 8.8°C). For the first time we report on spawning atresia where all components of the process are included in the estimate. In Irish Sea cod potential fecundity would make a close approximation (97–98%) to realised fecundity but this assumption was not valid for Barents Sea cod where spawning atresia accounted for a 14–18% fall in relative fecundity depending on the fish length. Batch fecundity was positively related to fish weight and declined as spawning progressed in both stocks especially in the Barents Sea but addition of fish length to the model was not significant. Relative condition declined in both stocks during spawning at the same rate but dropped by a greater proportion in Irish Sea cod. Individual egg dry weight was related to fish length and also declined during spawning. Overall fish size significantly affects some aspects of realised fecundity. [Copyright &y& Elsevier]

Abstract: Liver weight, relative condition (Kn), and somatic energy content have proven useful for predicting reproductive potential of fishes. Such proxy measures are advantageous in that they are easier to measure directly than fecundity and can often be measured in advance of spawning. We explored the utility of simple as well as more detailed measures of reproductive output in a laboratory experiment with black sea bass (Centropristis striata), an iteroparous, batch spawning protogynous hermaphrodite that may exhibit both determinate and indeterminate fecundity patterns within its geographic range. Wild fish were collected in fall, well ahead of spring-summer spawning, from two locations (Woods Hole, MA; Panama City, FL) representing mid-Atlantic and Gulf of Mexico stocks. To obtain a range in condition, fish were subject to either a high or low feeding regime for 4–5 months. During the experiment, length, weight, and bioelectrical impedance analysis (BIA) of individuals were monitored monthly. At the end of the experiment, additional individual measures taken included: relative gonad, liver, and viscera weights, absolute energy density, sex and maturity. As planned, these feeding treatments produced a range in sizes, fish of both sexes were developing or spawning capable, and the high ration group had higher Kn. This provided sufficient contrast to explore predictive relationships between total gonad energy (TGE) and terminal or prior biological measures. Examining multiple models with Akaike Information Criteria showed that final TGE was estimated with highest precision from a model including final sex, gonadosomatic index, length, Kn and liver energy density (89.1% deviance explained). The best model using nonlethal measures included BIA measured phase angle (PA) one month earlier, but much precision was lost (31.0% deviance explained). The explanatory power of PA, Kn, fish size, and stock also changed during the experiment, reflecting differences in the timing and magnitude of energy allocation and the difficulty in applying non-lethal measures to estimate TGE precisely in this species. Different energy allocation pathways were also apparent by stock. By the end of the experiment, mid-Atlantic black sea bass allocated more energy to liver and gonad whereas Gulf black sea bass allocated more energy to soma and viscera. We postulate that such intraspecific differences are adaptive in terms of the very different environmental conditions experienced by and the reported differences in spawning strategies by each stock, but this is rarely demonstrated in fishes and warrants further investigation. [Copyright &y& Elsevier]

Abstract: Seasonal variability in fecundity has been observed in a number of marine fishes and is important towards understanding the reproductive potential of a fish stock. However, the seasonal dynamics of egg production of Baltic sprat (Sprattus sprattus balticus S) have not been well described to date. We present data on the timing of spawning, and the seasonal variability in batch fecundity, number of developing oocytes, oocyte dry weight, spawning fraction, fish condition and atresia for this species in the Bornholm Basin, Baltic Sea. Histological techniques in combination with image analysis were applied to investigate those variables based upon material sampled in 2005 and 2008. Sprat were reported to be in spawning condition from January to June in each year plus in 2008 signs of ovarian maturation were also observed in November. Relative batch fecundity was found to vary two-fold with 85eggsg−1 ovary free body weight observed early in the spawning season (January 2005) and 165eggsg−1 ovary free body weight late in the spawning season (June 2008). Variability in batch fecundity during peak spawning was rather low. A seasonal decrease in oocyte dry weight was related to an increase in batch fecundity. Spawning fraction varied over the course of the spawning period with values ranging from 0.29 in March to 0.18 in June. Stereometric analyses confirmed the indeterminate fecundity of Baltic sprat. Prevalence of atresia was low during peak spawning in April to June (1.0–4.0%) but considerably higher during the early spawning period in March (16.4%) and highest in November (38.5%). Female sprat condition was low during the spawning period and increased sharply after spawning ceased. Our study provides a better understanding of fecundity and spawning dynamics of Baltic sprat which will aid to improve the assessment of reproductive potential of this ecologically and economically important fish species. [Copyright &y& Elsevier]

Abstract: In this study the reproductive investment of six populations of Atlantic herring (Clupea harengus) in Norwegian waters was contrasted in relation to trade-offs with body growth (relatively slow-relatively fast) and migration distance (stationary-migratory). Down-regulation of fecundity through the process of atresia as well as standardisation of fecundity to the prespawning stage were included as process-oriented reproductive factors, applying both histological and image analysis techniques. The further analysis included historic information on body growth as well as published information on fecundity from several stocks in the North Atlantic. The Norwegian spring-spawning (NSS) herring could be split into three sub-components: migratory (oceanic), likely semi-stationary (coastal) and stationary. The latter one as well as three other populations were sampled in relatively isolated semi-enclosed areas (pond, “lake” or fjord). The study documented clear signs of trade-offs: migratory herring had a significantly higher growth rate and lower relative fecundity while stationary populations grew slower and presented higher values of relative fecundity. So these traits appeared highly plastic and for the first time explicitly demonstrated in the three types of NSS herring: stationary NSS herring had high fecundity and body condition while the truly migratory counterpart was low in both while the intermediate version was low in fecundity but high in condition. The literature-based analysis of other Atlantic spring-spawning herring populations seemed to corroborate the finding that slow-growing herring is relatively more fecund than the faster-growing populations. [Copyright &y& Elsevier]

Abstract: Despite its importance in applied fish reproductive biology the fecundity pattern (determinate vs. indeterminate) is still an open question for many fish stocks, often hindering the selection of the appropriate egg production method for the estimation of stock spawning biomass. As a rule of thumb it is considered that cold-water, capital breeders with short spawning periods are determinate spawners while warm-water, income breeders with extended spawning periods are indeterminate spawners. However, the exact biological and/or ecological mechanisms that lead to the one, the other or intermediate patterns are still uncertain. The present review describes the evolving concepts on fish fecundity patterns and overviews the important theoretical and methodological advances on the assessment of fish fecundity. This information is subsequently used to provide refined lines of evidence on the correct designation of the fecundity pattern of fish stocks. Finally, this review attempts to shed light on the possible links between the fecundity pattern and the specific environmental conditions encompassed by fish stocks and suggest future perspectives and conceptual models that could be developed in order to better explain and predict the fecundity pattern in fishes. [Copyright &y& Elsevier]

Abstract: Annual fecundity has been increasingly advanced as a preferred measure of stock reproductive potential (SRP), yet estimates are methodologically challenging, particularly for species with indeterminate fecundity. Inherent variability due to energetic and environmental constraints increases the uncertainty of annual fecundity estimates, and this uncertainty may have important consequences for management guidance. In this study, we assessed how size-dependent reproductive timing interacts with age truncation to impact estimates of SRP in spotted seatrout (Cynoscion nebulosus), using a combination of modeling techniques. Positive size dependence in spawning frequency, or the number of spawning events in a season, had a substantial impact on both the SRP and estimates of stock status relative to management targets. The loss of the oldest age classes, even under relatively low fishing pressures, resulted in a significant decline in SRP due to the disproportionately large contribution by these age classes. Not surprisingly, the effect increased with the strength of the size-dependent relationship, which also resulted in reducing the proportionality between SRP and spawning stock biomass (SSB). The potential for erroneously classifying the health of a stock was amplified when the population approached the management target because of the uncertainty and inherent variability in SRP. For management, characterizing all of the size-dependent relationships with SRP (batch fecundity, reproductive timing, egg/larval quality) may be more critical than obtaining precise estimates of SRP when management reference points are relative to unexploited conditions, as in spawning potential ratios (SPRs). [Copyright &y& Elsevier]

Abstract: Understanding the causes of variation in stock reproductive potential (SRP) is challenging due to the difficulty in assessing the relative contribution of environmental, demographic and genotypic influences. This review explores how experimental and comparative field studies have been used to disentangle sources of variation in maturity, fecundity and the timing of spawning. By comparing reproductive parameters and corresponding environmental conditions among stocks of a species it is clear that demography, energetic state and temperature are important factors affecting variation in SRP. Common garden and environment experiments have confirmed that there is also a substantial genetic component to regional differences in reproductive investment and timing of spawning. Environmental manipulation experiments have helped to elucidate the proximate mechanisms underlying many reproductive processes. Together these different sources of information have provided a foundation for the development of statistical and individual based modelling approaches that help explain variation in SRP. In the near future, genomic investigations may provide a direct means to account for genetic influences on reproductive variation. Given that the age and size structure of many fish stocks has become truncated through fishing, a greater focus on the contribution of reproductive life span to SRP is also needed. [Copyright &y& Elsevier]

The present study assessed differences in fecundity and egg quality from Atlantic cod Gadus morhua fed isoproteic diets containing 13% fat (low fat, LF) or 20% fat (high fat, HF) and either stressed or left unstressed as a control over the spawning season. Each diet was fed to triplicate groups of G. morhua from June 2009, through to first maturation and spawning. In January 2010 sub-groups of G. morhua were moved to land-based spawning tanks where the experimental trial was carried out. At the start of the experiment, G. morhua fed the high-fat diet were significantly larger than G. morhua fed low-fat diet. These differences were maintained through the spawning season, although with a loss of mass in both dietary groups. Relative fecundity through the season was significantly lower in stressed G. morhua fed LF compared to unstressed G. morhua fed the same diet. Stressed G. morhua had a higher variability in weekly amount of eggs spawned, spawning occurred more irregularly, and the spawning period lasted longer than in unstressed G. morhua. Several egg quality variables were also affected: eggs from G. morhua fed LF and exposed to stress had lower fertilization and hatching rates compared to the unstressed G. morhua fed the same diet as well as all G. morhua fed HF. Gadus morhua fed a low-fat diet appeared less tolerant to stress than fish fed a high-fat diet. [ABSTRACT FROM AUTHOR]

The present study is the first to provide data on the reproductive biology of cuckoo ray Leucoraja naevus in Portuguese continental waters. No difference in size at maturity was detected between sexes, which was estimated as 56 cm total length. Spawning occurs all year round, but maximum activity was during winter months. Maximum fecundity is c. 63 eggs female−1 year−1. Encapsulated eggs are released in batches, nine in total with a mean number of seven extruded eggs in each batch. [ABSTRACT FROM AUTHOR]

Timing of spawning and hatching of shortnose sturgeon, Acipenser brevirostrum, in the Saint John River, New Brunswick, Canada, was estimated using inverse prediction. We examined egg incubation periods at 5, 9, and 13 °C to back-calculate spawning dates. No larvae hatched at 5 °C. At 9 and 13 °C, hatching began after 18 and 8 days post fertilization, respectively. Lengths of yolk-sac larvae reared in the laboratory at 13-21 °C were used to develop a temperature-mediated Gompertz growth model. The inverted Gompertz model, predicting larval age from larval size and water temperature, was applied to 671, 164, and 746 larvae captured in the wild in 2008, 2009, and 2010, respectively. Estimated hatching distributions peaked in late May, and mean spawning events were predicted to occur in late April - early May (9 °C scenario) and middle to late May (13 °C scenario). Larval ages at the two sampling transects, 4.5 km apart, were similar, while catch per unit effort was lower downstream, indicating mortality during dispersal. Inverse prediction of larval ages provides fast and cost-effective estimates of the timing of spawning, hatching, and larval migration in the wild. [ABSTRACT FROM AUTHOR]

Abstract: The effects of acute or sustained administration of mammalian and salmon GnRH agonists (mGnRHa and sGnRHa) were examined on the reproduction performance of wild-caught female carp from the Caspian Sea. Ripe broodfish were caught in the beginning of spawning season (early May) by seine from the southeast coastal waters of the Caspian Sea, Golestan province, Iran. To induce spawning fish were allocated into 8 groups and treated with 7% physiological saline (control), 4mgkg−1 carp pituitary (CP) extract (positive control), 20μgkg−1 mGnRHa or sGnRHa together with 40mgkg−1 Metoclopramide (acute treatments), a cholesterol pellet containing 20μgkg−1 mGnRHa or sGnRHa together with 40mgkg−1 Metoclopramide, and emulsified GnRHa in Freud''s Incomplete Adjuvant (FIA) containing 20μgkg−1 mGnRHa or sGnRHa together with 40mgkg−1 Metoclopramide (mGnRHa-FIA and sGnRHa-FIA). After the final injection the fish were checked for spawning regularly. Ovulated fish were stripped manually and the eggs fertilized artificially. Significant differences were observed in the reproduction success, latency period and practical fecundity among treated groups (p ≤0.05). Injection of CP or sGnRHa in acute or sustained methods increased significantly the reproduction success compared to acute injection, implanting of mGnRHa or controls (p ≤0.05). In spite of the weaker effect of mGnRHa injection or cholesterol implant on induction of ovulation, treatment with mGnRHa-FIA showed similar effects as sGnRHa-FIA. Almost all sustained delivery systems of both GnRHa enhanced the practical fecundity of treated fish compared to CP and acute GnRHa injections. The latency periods of fish that received GnRHa-FIA and implant were near 24 and 50h, respectively, which were significantly longer than that of fish given an acute GnRHa treatment or CP (p ≤0.05). There was no significant difference in fertilization and hatching success of the produced progeny among treated groups (p ≥0.05). The results showed that injection of GnRHa in FIA increased significantly the ovulation success of fish, but implanting fish with mGnRHa in a cholesterol pellet had variable effects with increasing fecundity but not higher ovulation success, compared to the CP treatment. [Copyright &y& Elsevier]

In this study, sex ratio, spawning season, fork length ( LF) at maturity ( LF50), batch fecundity and spawning frequency were characterized for the continental population of Ocyurus chrysurus from the Campeche Bank, in the southern Gulf of Mexico. A total of 1657 specimens were collected from February 2008 to January 2009. The overall sex ratio (male:female) and sex ratios by size-class showed no significant differences from an expected 1:1 ratio. The Campeche Bank population did not conform to the reproductive seasonality pattern characteristic of a continental population. A protracted spawning season that extended from January to September with peaks occurring mainly between April and May and additionally in September was observed. The population conformed, however, to the sexual maturity pattern observed for populations and species associated with a continental margin. Fish of both sexes reached the onset of sexual maturity at a similar and small LF of c. 14 cm, and LF50 ( LF at which 50% of females and males become mature) was 21·3 and 19·4 cm. Asynchronous-type ovarian development was observed for this species and batch fecundity estimates ranged from 14 102 to 164 756 oocytes (mean ± s.d. = 43852 ± 32684 oocytes). The overall spawning frequency estimate was once every 8·3 days or 26 times during the 9 month spawning season. [ABSTRACT FROM AUTHOR]

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

Abstract: Absolute and relative batch fecundity of Baltic sprat (Sprattus sprattus balticus S.) during peak spawning time was investigated for several years over the last two decades by applying the hydrated oocyte method. Batch fecundity was analysed for three important spawning areas of sprat in the central Baltic Sea, namely the Bornholm Basin, Gdansk Deep and Southern Gotland Basin. Environmental parameters such as hydrography, fish condition and stock density were tested in order to investigate the observed variability in sprat fecundity. Absolute batch fecundity was found to be positively related to fish length and weight. Significant differences in absolute and relative batch fecundity of Baltic sprat among areas and years were detected, and could partly be explained by hydrographic features of the investigated areas. A non-linear multiple regression model taking into account fish length and ambient temperature explained 70% of variability in absolute batch fecundity. Oxygen content and fish condition were not related to sprat batch fecundity. Additionally, a negative effect of stock size on sprat batch fecundity in the Bornholm Basin was revealed. The obtained data and results are important to assess the stock reproductive potential of this important Baltic fish stock. [Copyright &y& Elsevier]

Variation in brood abandonment was explored by conducting partial brood removals from smallmouth bass, Micropterus dolomieu Lacepède, nests in two north temperate lakes. In both lakes, percent of the brood removed had no effect on nest failure rates. Nest failure prior to offspring swim-up was more common, but unrelated to brood size after removal, in the lake with higher post-spawning mortality and lower growth and fecundity. Brood size after removal was negatively related to nest failure in the lake with high survival, growth and fecundity. Nests guarded by young males failed more frequently than those of old males, and young broods failed more frequently than old broods. Dynamic programming and logistic regression models developed to predict nest fate worked better for the lake with selective pressures that theoretically favoured abandonment (e.g. high post-spawning mortality). Both models identified male age and brood age as important factors in predicting nest fates. Because nest success is related to the age of the parent, this could have consequences for overall nest success for populations with different demographics. [ABSTRACT FROM AUTHOR]