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

12 páginas, 11 figuras.-- Scientific Council Meetin

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

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

Histological Assessment of Sexual Maturity in Greenland Halibut in Div. 3LM

11 páginas, 6 tablas, 1 figura.-- Scientific Council Meetin

Histological Assessment of Sexual Maturity of the Flemish Cap Cod (Division 3M) in 1995

6 páginas, 5 tablas, 2 fisguras.-- Scientific Council Meetin

Sexual Maturity of Cod (Gadus morhua) in Flemish Cap (Div. 3M)

6 páginas, 3 tablas, 2 figuras.-- Scientific Council Meetin