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Fecundity of redfish Sebastes mentella and Sebastes norvegicus in the Irminger Sea and Icelandic waters was analyzed in relation to several maternal features and oocyte developmental stages. The mean potential fecundity in S. norvegicus was estimated to be 123,300 oocytes and relative fecundity averaged 116 oocytes g-1. Mean potential fecundity in S. mentella was 50,013 oocytes and relative fecundity was 64 oocytes g-1. Strong fecundity down-regulation (50% on average) was observed during oocyte development estimated from September to November, when oocytes reached the advanced stage of vitellogenesis. This result implies that fecundity can only be comparable between individuals presenting the same stage of oocyte development. However, the development rates differed between species and between stocks, and therefore the same stage is reached at a different time of the year. Fecundity varied significantly with female weight and length, while condition had little influence on fecundity variation. [ABSTRACT FROM AUTHOR]

Fisheries ecologists traditionally aimed at disentangling climate and fishing effects from the population dynamics of exploited marine fish stocks. However, recent studies have shown that internal characteristics and external forcing (climate and exploitation) have interactive rather than additive effects. Thought most of these studies explored how demographic truncation induced by exploitation affected the response of recruitment to climate, identifying a general pattern revealed to be difficult as interactions are often case-specific. Here we compared five exploited stocks of European hake Merluccius merluccius from the Atlantic Ocean and Mediterranean Sea to investigate how the interaction between internal characteristics and external forces affect the variability of the population growth rate and their consequences on recruitment. Our results show that demographic truncation induces a novel population scenario in which the growth rate is maximized when the reproductive stock is younger and less diverse. This scenario is shaped by the climate variability and the fishing pattern. The population growth rate becomes more dependent on the maturation schedule and less on the survival rates. The consequences for the recruitment dynamics are twofold; the effect of density-dependent regulatory processes decreases while the effect of the density-independent drivers increases. Our study shows that the interaction between internal characteristics and external forces changes across geographic locations according to 1) the importance of demographic truncation, 2) the influence of the climate on the regional hydrography and 3) the spatiotemporal heterogeneity of the physical environment to which fish life history is adapted. [ABSTRACT FROM AUTHOR]

Abstract: Proximate composition and energy content in Trisopterus luscus have been studied to address energy allocation strategy. Energy reserves in pouting females are mainly associated with lipids stored in the liver. Water content appeared to be a useful index in order to obtain very accurate predictions of energy density, particularly for ovaries and liver. Condition indices, HSI and K, are suitable to analyze nutritional status of fish, since they reflect changes in energy content and proximate composition in the different tissues studied. The seasonality of energy reserves was detected and is closely related to the sexual cycle, indicating that females pouting display a period of energy storage, mainly through lipid deposition in the liver. Therefore, T. luscus should be considered a capital rather than an income breeder, as the energy for reproduction comes essentially from stored energy. [Copyright &y& Elsevier]

Copyright of Canadian Journal of Fisheries & Aquatic Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Aquatic Living Resources is the property of EDP Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A histological method is used to detect the proportion of both adult and recruit females at the beginning of gonad development, in summer, a few months after spawning. At this time it is difficult to make a visual diagnosis of the sexual maturity stage. The proportion of females with postovulatory follicles is used to determine the length and age at maturity in the year of sampling, and the proportion of females in the cortical alveoli and/or vitellogenic stages is used to estimate the same parameter for the following year. Variations in age and length at maturity during the period 1992–1995 were analysed by comparing the respective maturity curves of both the “previous spawners” and the “next-year spawners” females. A drastic decrease in both the age and the length at maturity is observed in this period and it seems likely that the age at maturity of female cod became fixed at around age 3 at the end of the period analysed. The possibility that this could be a density-dependent response of the stock at the Flemish Cap is discussed. [ABSTRACT FROM PUBLISHER]

Information on temporal variations in stock reproductive potential (SRP) is essential in fisheries management. Despite this relevance, fundamental understanding of egg production variability remains largely unclear due to difficulties in tracking the underlying complex fluctuations in early oocyte recruitment that determines fecundity. We applied advanced oocyte packing density theory to get in-depth, quantitative insights across oocyte stages and seasons, selecting the commercially valuable European hake (Merluccius merluccius) as a case study. Our work evidenced sophisticated seasonal oocyte recruitment dynamics and patterns, mostly driven by a low-cost predefinition of fecundity as a function of fish body size, likely influenced also by environmental cues. Fecundity seems to be defined at a much earlier stage of oocyte development than previously thought, implying a quasi-determinate – rather than indeterminate – fecundity type in hake. These results imply a major change in the conceptual approach to reproductive strategies in teleosts. These findings not only question the current binary classification of fecundity as either determinate or indeterminate, but also suggest that current practices regarding potential fecundity estimation in fishes should be complemented with studies on primary oocyte dynamics. Accordingly, the methodology and approach adopted in this study may be profitably applied for unravelling some of the complexities associated with oocyte recruitment and thereby SRP variability. [ABSTRACT FROM AUTHOR]

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]

Flemish Cap is an isolated fishing ground located in the international waters of the Northwest Atlantic Fisheries Organization area (NAFO). In the last decades, the Flemish Cap demersal community has been subjected to strong and variable fishing intensities affecting different stocks over time. In this work, three ecological indices for individual populations (abundance, biomass, and intrinsic population rate of growth) and five community indicators (total abundance and biomass, community synchrony, ABC curves and proportion of non-commercial/commercial species) have been applied to data of 29 fish and 1 shrimp species to analyse the dynamics of the whole ecosystem and the major demersal fish assemblages. Different periods were detected, which may be explained by differences in the exploitation patterns and pressure for different stocks, prey-predators relationships and other environmental drivers affecting the reproductive capacity. This study shows that the selected community indicators are appropriate to detect changes in the demersal community of Flemish Cap in response to fishing, predation and variability in recruitment success. It has been also demonstrated that treating each depth zone separately help us to better understand trends and that analyses revealed different trends for different parts of the community during periods with different fishing pressure. This knowledge could be useful to support management policies. [ABSTRACT FROM AUTHOR]

Abstract: Flemish Cap cod Gadus morhua, as with many other fish populations subjected to high fishing rates, has experienced variation in size and age at maturation. Following intense fishing activity and concurrent with a substantial decline in population biomass, cohorts in the early 1990s exhibited a reduction in the length and age at which there is a 50% chance of being mature (L 50 and A 50 respectively) with values lower than ever estimated before. A further decline in A 50 (not in L 50) was found after the cod fishing moratoria, in late 1990s and early 2000s cohorts. At the same time, the water temperature showed substantial changes and the abundance of the main prey species of juvenile cod experienced large variation. Shrimp replaced hyperiids as the main prey item since the late 1990s, which was followed by large changes in feeding habits, fish condition and mean size at age. The analysis of maturation reaction norms and countertrend variations in growth rate, water temperature and condition support the hypothesis of genetic change as the main explanation for the decline in size and age at maturation of the cohorts of the late 1980s and early 1990s. However the change in A 50 in the late 1990s and early 2000s cohorts is suggested to be caused mainly by a phenotypic response as a consequence of variation in feeding opportunities, water temperature and density-dependent changes in growth rate. If food availability decreases and there is a decrease in water temperature, a decrease in the reproductive potential and survivorship may be expected. [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]