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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]

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]

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]

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 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]

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]

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]

Abstract: The Atlantic croaker Micropogonias undulatus Linnaeus 1766 is a candidate for multiple purpose aquaculture production including use as a baitfish and foodfish. Controlled production of Atlantic croaker could alleviate seasonal availability, establish a steady supply, provide size-specific grades of bait, alleviate pressure on wild stocks, diversify aquaculture businesses, and contribute to foodfish sales. To achieve these potential benefits, development of commercial-scale spawning protocols must occur. Therefore, a study was conducted to determine: 1) if Atlantic croaker could be passively spawned in a captive environment; 2) if hormone implants could be used to actively spawn Atlantic croaker or improve fecundity; 3) if environmental control and hormone implants could be used to synchronize spawning of Atlantic croaker. Wild broodfish (mean±SE; 329±11g; 28.7±0.3cm TL) were captured from Trinity Bay, Texas, pellet trained, and held under controlled photoperiod and temperature conditions. The treatments used were: 1) natural spawning (no hormone treatments); 2) pre-optimal temperature hormone implant (implant injected at 25°C; 75μg salmon gonadotropin-releasing hormone analogue; sGnRHa); 3) optimal temperature hormone implant (implant injected at 23°C; 75μg sGnRHa); or 4) post-optimal temperature hormone implant (implant injected at 21°C; 75μg sGnRHa). The total production from all treatments (N =36 females; 24 males) included 30 total spawning events during the 120day study, which yielded 2,922,510 eggs (3064mL eggs). The mean water temperature and photoperiod at time of spawning were 19.9°C and 10.1 h of daylight, respectively. The post-optimal implant treatment resulted in a greater number of spawning events per tank (5.0±0.0), the shortest period of latency (3±0 days), larger volume of eggs·spawning event (170±40mL), greater quantity of eggs·spawning event (160,203±37,943), and greater fertilization rate (51.9±5.6%) than the other hormone implant treatments. The fish allowed to spawn naturally or in the post-optimal treatment often produced similar results, but fish in the post-optimal treatment produced more spawns per tank (5.0±0.0 compared to 1.7±0.3), had greater fecundity (267,004±33,191 eggs·female compared to 49,090±22,061 eggs·female), and spawning was highly synchronized (5days compared to 33days). The results of this study demonstrate that Atlantic croaker can be spawned passively in a captive environment, but hormone implants used to actively induce spawning can improve fecundity and synchronize spawning for commercial production. [Copyright &y& Elsevier]

Abstract: Stock recruitment (SR) relationships aim to predict the recruitment based on a given level of reproductive stock. Though the spawning stock biomass (SSB) is commonly used to fit such SR models, there is increasing evidence that the total egg production (TEP) is a more relevant stock reproductive potential index. Indeed, the TEP takes into account both the size-dependent capacity of females to produce eggs and the demographical structure of the spawning stock. This paper presents a method to assess the TEP based on the fecundity and egg quality based on the age as well as spawning fraction for the southern stock of European hake (Merluccius merluccius). The fecundity and egg quality increased significantly as the female size increased. The spawning fraction also increased with female size. Larger females concentrated their reproductive period during the first quarter of the year, whereas smaller ones spawned throughout the year. The stock''s demographic structure showed a clear increase in the proportion of younger females and a reduction of older ones through the 1982–2007 time-series, which led to a decrease of egg production per unit of female SSB. Our results showed a significant contribution of older individuals to the reproductive output. The relevance of using TEP as an index of stock reproductive potential is discussed. [Copyright &y& Elsevier]

Abstract: Some fish species have wide distribution areas that span very different habitats. In this investigation we have studied Atlantic cod (Gadus morhua), which is an example of such a species, to demonstrate how this may have caused adaptations to key features such as fecundity, growth and age and size at first spawning. We have studied cod from the Barents Sea, Icelandic waters, North Sea and Irish Sea. The ovary sampling was undertaken over several years, however, not always sequentially, in order to assess whether the relationships between fecundity and other key features were constant or variable. Also, we compared historical maturity ogives and growth from the different regions. There was a clear pattern with fish maturing at a greater age and size in the north compared to the south. For three of the four cod stocks we demonstrated a significant reduction in relative potential fecundity as maturity progressed towards spawning, i.e., as the mean diameter of vitellogenic follicles increased. To be able to compare potential fecundity in a standardised way both in time and space, we constructed models that included mean diameter as one of the independent variables. Our potential fecundity comparisons clearly indicated a north-south gradient with increasing size-specific fecundity towards the south. The higher fecundity of the fish in the south could only partly be explained by the higher condition and temperature that was observed in these waters. [Copyright &y& Elsevier]

Red snapper (Lutjanus campechanus) is a popular marine sportfish and is a significant part of the commercial fisheries in the Gulf of Mexico. It can be reproduced under hatchery conditions by induced spawning of wild-caught adults or by conditioning wild-caught adults to spawn naturally under controlled conditions. Mature females (Gondosomatic Index ω 1) occur in the northern Gulf of Mexico from May to September. When such females were collected off the Alabama coast and induced to spawn with HCG, 56 ± 17.3% of the females ovulated. Fecundity (ovulated floating eggs) varies, for 60 spawns averaged 197,212 ± 173,349 eggs/kg female. Percent hatch averaged 42.1 ± 3.44%. Wild-caught adult red snapper can be held in confinement and natural spawning obtained when temperature and photoperiod are controlled. Adult snapper held in 13.2-m3 tanks (8-10 fish/tank), where photoperiod and temperatures were adjusted, spawned naturally 63 times over a 105-day period, with a mean egg production/tank of 4.2 million eggs. Mean fertilization rate, hatch rate, and survival at 36-40 hph were 90.5%, 83%, and 49%, respectively. Natural spawns produce better quality seed, but the occurrence of fertilized spawns is unpredictable. Hormone-induced spawns are easier to schedule but egg quality can be variable. [ABSTRACT FROM AUTHOR]

Rosylip sculpin Ascelichthys rhodorus spawned in the intertidal during the winter in the north-eastern Pacific. Large numbers of males typically congregated at spawning sites, where females deposited clutches. The mating system of this species was external fertilization and group spawning at specific oviposition sites under boulders in the intertidal, and no alternative male mating strategies. Males were abundant at sites while oviposition was occurring, and most abandoned the sites as spawning tapered off seasonally despite the presence of developing clutches. Experimental removal of males from sites suggested that males provided some short-term benefits to clutches, with catastrophic loss of clutches significantly lower when males were present. The large number of males at an oviposition site and histological evidence indicating high sperm production and storage of sperm prior to release suggest a high level of sperm competition in this species. This spawning pattern appears to differ in substantial ways from any other reported fish mating system. [ABSTRACT FROM AUTHOR]

The development stage and number of seed (eggs and fry) removed from individual incubating Oreochromis niloticus (L.) broodfish at 10-day interharvest intervals (IHI) was compared with the harvest of free-swimming fry from undisturbed fish held in a tank within the same system. Spawning synchrony and productivity were compared for (1) total exchange of females for 'conditioned' females after each harvest, (2) exchange of only spawned females, and (3) return of females back into the spawning tank. Improved synchrony and seed production were positively related to removal of eggs and fry from incubating females and could have important implications for broodstock management in commercial hatcheries. Allowing fish to remain undisturbed in clear water tanks may lead to inhibition of spawning activity related to the formation of hierarchies. Individual weight loss by females during incubation was correlated with stage of seed harvested and thus with timing of spawning during the interharvest interval. [ABSTRACT FROM AUTHOR]

This study evaluated the reproductive parameters and genetic variability of offspring of Rhamdia quelen from mating by natural spawning and by controlled fertilization with fresh and cryopreserved semen. After hormonal manipulation, three R quelen pairs were used for natural spawning in high-flow tanks, three pairs were used for mating with fresh semen, and another three pairs were used with cryopreserved semen. Matings were performed in triplicate. For matings with fresh and cryopreserved semen, semen from each male was used to individually fertilize oocytes from each female. Pools of semen and oocytes were made, and aliquots of these gametes were taken for fertilization. No differences (P > 0.05) were detected for absolute or relative fecundity, fertilization rate, or egg hatching rate. The use of fresh semen led to a higher (P < 0.01) percentage of normal larvae. The use of fresh semen in pooled mating resulted in a greater effective number of alleles and a higher expected heterozygosity. Offspring from natural spawning presented higher observed heterozygosity and a lower inbreeding coefficient. The highest inbreeding coefficient was found in offspring from individual matings using fresh semen. Regarding paternal contributions, a single male dominated in matings with fresh semen, whereas two males dominated in natural spawning and matings using cryopreserved semen. The use of gamete pools for mating and natural spawning resulted in higher genetic variability of offspring, and mating using cryopreserved semen found no effects on genetic variability of offspring but did reduce the percentage of normal larvae. Other reproductive parameters were not influenced by spawning strategies. [ABSTRACT FROM AUTHOR]