Distribution, abundance and biomass trends of the genus Sebastes on Flemish cap (division 3M)

12 páginas, 11 figuras.-- Scientific Council Meetin

Sexual maturity and spawning biomass of the cod stock on flemish cap (division 3M)

11 página, 5 tablas, 3 figuras.-- Scientific Council MeetingIn recent years, in Flemish Cap cod has been observed a progressive reduction on age and size at maturity from 1992 to 1995 (Saborido-Rey and Junquera, 1998). This reduction was probably a response to low population abundance and accordingly a certain recovering of the spawning biomass would be expected. However there was a lack of incoming recruitment in the latest years, which make the biomass of the Flemish Cap cod being in the lowest value recorded. Despite of the improvement in the scientific advice with the incorporation of new models in terms of uncertainty, the lack of biological realism can produce an inappropriate model assumptions, as for example those concerned with static life history parameters (Helser and Brodziak, 199-8). Several studies conftrm that population density is an important mechanism in regulating the dynamics of marine ftsh populations (TrippeL 1995; Tyler et aI., 1997) affecting to several life history parameters, as growth and age/size and maturity (Roff, 1984) and hence the possibility of the spawning biomass to increase in order to permit the rebuilding of the stock. Size and age at maturity of the Flemish Cap female cod has been determined by an histological method since 1990 at summer, when the ED-survey is carried out. The method uses cod ovaries in the cortical alveoli stage as an index of the onset of the oocyte development for the next breeding season, whereas the presence of postovulatory follicles in the ovaries shows the already spawned females (Zamarro et aI., 1993). The cortical alveoli are the ftrststructures to appear during the phase of oocyte growth (Wallace and Selman, 1981), and therefore they are the ftrst sign of the start of the female ripening before the beginning of the vitellogenesis. The postovulatory follicles are the structures left in the ovary after maturation is ftnished and oocyte ovulation. The spawning season of the. Flemish Cap cod is known to be short in time and the earliest in the year of all cod stocks in the Northwest Atlantic (Myers et aI., 1993); it occurs around March. This method allow to accurately detect the proportion of both recruit and repeat mature females at the very beginning of the gonad development, as it happens in summer, few months after spawning, when it is very difficult to make a visual diagnosis of the sexual maturity stage (Morrison, 1990). In this paper the proportion of females with postovulatory follicles in July 1998 is used to determine the size and age at maturity in 1996 and the proportion of females in the cortical alveoli stage to estimate the same parameters for 1999. Estimation of the spawning stock biomass is calculated and its evolution in the period 1990-1998 discusse

Digestive enzymes in marine species. II. Amylase activities in gut from seabream (Sparus aurata), turbot (Scophthalmus maximus) and redfish (Sebastes mentella)

8 páginas, 3 tablas, 3 figurasThe amylase activity of the digestive tract of three carnivorous fish species (Spurus aurata, ScophtMmw maximus and Sebustes me&la) has been studied. The activity of seabream and turbot showed its maximum at neutral pH (7.0-7.5); meanwhile, the activity of redfish had an optimum pH at 4.5-5.0. The to function ranged between 35 and 45°C for the three species. The Arrhenius plots of the intestinal activities of seabream and turbot showed breakpoints at temperatures close to those of their physiological activities. High saline concentrations inhibited the activity of seabream and turbot and activated the activity of redfish. Seabream activity was absolutely dependent on calcium ions. On the contrary, redfish activity was only detected in the absence of this metal. Studies carried out by using several effecters suggested that the activities found in these three species are different. Considering our results from a point of view of the environmental conditions of these species, it might be concluded that enzymatic digestion of dietary carbohydrates proceeds at very low rate. Physiologicat implications are discussedThis work was supported b a grant from the Xunta de Galicia XUGA40201 B90.Peer reviewe

I Simposio Iberoamericano de Ecología Reproductiva, Reclutamiento y Pesquerías

12 páginas, 1 tabla, 1 figuraPeer reviewe

Historical gene flow constraints in a northeastern Atlantic fish: phylogeography of the ballan wrasse Labrus bergylta across its distribution range

14 páginas, 3 figuras, 3 tablas.-- Frederico Almada ... et al.-- Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, provided the original author and source are creditedThe distribution and demographic patterns of marine organisms in the north Atlantic were largely shaped by climatic changes during the Pleistocene, when recurrent glacial maxima forced them to move south or to survive in northern peri-glacial refugia. These patterns were also influenced by biological and ecological factors intrinsic to each species, namely their dispersion ability. The ballan wrasse (Labrus bergylta), the largest labrid fish along Europe's continental margins, is a target for fisheries and aquaculture industry. The phylogeographic pattern, population structure, potential glacial refugia and recolonization routes for this species were assessed across its full distribution range, using mitochondrial and nuclear markers. The existence of a marked population structure can reflect both recolonization from three distinct glacial refugia and current and past oceanographic circulation patterns. Although isolated in present times, shared haplotypes between continental and Azores populations and historical exchange of migrants in both directions point to a common origin of L. bergylta. This situation is likely to be maintained and/or accentuated by current circulation patterns in the north Atlantic, and may lead to incipient speciation in the already distinct Azorean population. Future monitoring of this species is crucial to evaluate how this species is coping with current environmental changesThis study was funded by the Eco-Ethology Research Unit Strategic Plan (PEst-OE/MAR/UI0331/2011)—Fundação para a Ciência e a Tecnologia—FCT (partially FEDER funded), now included in MARE (UID/MAR/04292/2013). F.A. (SFRH/BPD/63170/2009) and S.M.F. (SFRH/BPD/84923/2012) were supported by FCT grants. C.S.L. was supported by MARE-ISPA/BI/004/2015. D.V.-R. was supported by a Marie Curie Intra European Fellowship within the 7th European Community Framework Programme (grant no. 625852). Sampling in the Azores was supported by CLIPE (PRAXIS/3/3.2/EMG/1957/95) and in continental Iberia by the European Science Foundation's MarinERA project ‘Marine phylogeographic structuring during climate change: the signature of leading and rear edge of range shifting populations'Peer reviewe

Buoyancy of Atlantic cod larvae in relation to developmental stage and maternal influences

17 pages, 5 figures, 7 tables.In this experimental study on Atlantic cod, Gadus morhua, buoyancy was found to vary significantly with season, developmental stage, egg size and maternal condition. Before the start of the experiments, wild fish were caught in the Barents Sea and acclimatized to laboratory conditions. Pairs (n = 8), one female (recruit spawner) and one male, spawned naturally in large, indoor compartments of a circular tank and every third egg batch (out of up to 19 batches collected per female) was incubated in aquaria. Following sedation (50 mg l-1metomidate hydrochloride, 30 min), individual larval specific gravity was precisely reported (30 min) using a density-graduated column. Larval specific gravity (meant) increased steadily during the first early stages of development (0–25 day-degrees), remained nearly constant during the following stages (25–35 day-degrees), but then decreased gradually (35–55 day-degrees). In general, late-season larvae were significantly less buoyant, i.e. showed higher meant, than early-season larvae. Meantwas negatively correlated with female condition and egg size and dry weight. Possible implications of these findings for drift and survival are discussed.This study was supported by the Training and Mobility of Researchers Programme, EU Contract No ERBFMBICT960772 (F.S.-R.). The writing-up of this paper was also supported by EU Contract No FAIRCT- 98-4122, STEREO (O.S.K. and A.T.).Peer reviewe

A review of an emerging tool to estimate population parameters: the close-kin mark-recapture method

Knowing the number of individuals in a population is fundamental for the sustainable management of exploited marine resources but estimating this parameter is often extremely challenging, especially in large, highly mobile and dispersed populations. Abundance estimation traditionally relies on multiple data types that include the relationship between fishery catches and effort (Catch Per Unit Effort or CPUE), scientific research surveys and demographic models that are developed to estimate past and current stock dynamics, but uncertainty is often high. Close-kin mark-recapture (CKMR) is an alternative method for estimating abundance and other demographic parameters (e.g. population trend, survival rates, connectivity), using kinship relationships determined from genetic samples. This methodology is based on a simple concept - the larger the population the less likely to find relatives and vice versa - and was proposed two decades ago although regained considerable attention recently. Refinements in the statistical methodology and advances in high throughput sequencing methods have boosted the efficiency of genomic analysis, promising to revolutionize the field of fisheries stock assessments. In theory, it can be applied to almost any species, provided that there is sufficient information about the life-history/biology of the organism and that the populations are not so small as to be almost extinct or so large that finding relatives becomes extremely difficult. Thus, it has the potential to provide baseline data for the many exploited fish stocks that remain largely unassessed and to reduce uncertainty in those that are regularly evaluated. Here, we provide an overview of the method in the context of fisheries assessments, analyze the advances and synthetize the field studies published in the last five years. Moreover, we evaluate the readiness, viability and maturity of the method to infer demographic parameters in species spanning diverse life histories. We evaluate technical considerations and requirements for a successful application and analyze the main challenges and limitations preventing a broader implementation

Incidencia y significancia de las estructuras císticas en ovarios de gádidos

Fish regulate egg production by atresia. Sometimes, oocytes are encapsulated in cystic structures that might remain in the ovary for months, altering female reproductive potential in future spawning seasons. Ovaries of Atlantic cod (Gadus morhua, L.) from the Flemish Cap and European hake (Merluccius merluccius, L.) from the Galician Shelf (NW Spain) were analysed from 1999 to 2006. The prevalence and abundance of ovarian cysts were estimated. Cyst prevalence increased with female size and/or age for both species, and decreased with high condition factor in hake. Cyst intensity does not correlate with any analysed factor. The size/age structure of spawning stock biomass and female condition could affect the prevalence of cysts in the ovaries, though it does not seem to affect cyst intensity in the ovary. Further research is needed to determine cyst resorption time and the impact that it has on egg production and consequently on stock reproductive potential.Los peces regulan la producción de huevos a través de la atresia. En ocasiones, los ovocitos son encapsulados en estructuras quísticas que podrían permanecer en el ovario durante meses, alterando el potencial reproductivo de las hembras en estaciones de puesta posteriores. Se tomaron ovarios de bacalao (Gadus morhua, L.) de Flemish Cap y de merluza europea (Merluccius merluccius, L.) de la costa gallega (NO España) entre 1999 y 2006. Se estimó la prevalencia e intensidad de quistes en estos ovarios. En ambas especies la prevalencia de hembras con quistes aumentó con la talla y/o edad y disminuyó al aumentar el factor de condición en el caso de la merluza. La intensidad de quistes no se correlacionó con ninguna de las variables estudiadas. La estructura de talla/edades del stock reproductor y la condición de las hembras podría afectar la prevalencia de hembras con quistes. Son necesarios más estudios para determinar el tiempo de reabsorción de estos quistes y las consecuencias que esto puede tener en la producción de huevos y por tanto en el potencial reproductivo de los stocks

Age and growth of redfish (Sebastes marinus, S. mentella, and S. fasciatus) on the Flemish Cap (Northwest Atlantic)

12 pages, 5 figures.-- Presented at the NAFO Deep-Sea Fisheries Symposium (Varadero, Cuba, Sep 12-14, 2001).Age determination of redfish is difficult. In this paper, the ages of Sebastes mentella on the Flemish Cap are validated by following year classes from 1991 to 2000. The criteria used for S. mentella are consistent and coherent. The growth of different year classes is described and compared, and density-dependence is demonstrated to influence the growth rate of the strong 1990 year class, growth of that year class being the slowest of those followed. The slow rate of growth prevented that year class from maturing at the anticipated age. Growth is also compared between sexes, of S. mentella, S. marinus, and S. fasciatus, revealing that females grow faster than males. Finally, growth rate is compared among species. S. marinus grows fastest and S. mentella slowest, although the influence of density-dependent growth in S. mentella needs to be taken into consideration.The study was supported by the European Commission through several research projects.Peer reviewe