cod is a major target species for the European fishing fleet.
All European cod stocks are under heavy fishing pressure or overexploited.
An effect of are overexploitation is a reduction in the average
age and size, with an increasing proportion of first-time spawners
in the stock. The basis for this project is to follow offspring
from selected families (pairs) of cod reared under identical and
semi-natural conditions from hatching, through the larval and
juvenile stages, and until sexual maturity, and compare their
viability through these stages. Viability comparisons will be
made between and within first-time (recruit) female spawners and
elder (repeat) female spawners. The investigation will improve
our understanding of the relative importance of individual genetic
variation compared to maternal effects on growth and survival
of cod, and the results will be incorporated into management models
to study how to improve fishery management strategies.
basis of this project is to follow offspring from selected families
of cod reared under identical and semi-natural conditions from
hatching, through the larval and juvenile stages, and until sexual
maturity, and compare their viability through these stages. Comparisons
of viability will be made between and within the two main experimental
groups: first-time female spawners, and elder female spawners.
The main objectives are:
examine the viability of offspring from first-time female spawners
compared to offspring from elder female spawners of Atlantic cod.
2.To examine variations in viability between offspring of individual
pairs of cod.
3.To analyse the demographic structure (age-, sex- and maturity
structure) of selected European cod stocks by means of historical
4.Based on the results of objectives 1., 2. and 3., to evaluate
the possible effects on cod recruitment and implications for fishery
The first two points will be examined by employing rearing experiments
in large marine enclosures (mesocosms: 2,500 and 4,400 m3). The
major viability measures are: growth, condition, and survival.
These measures will be taken during the larval and juvenile stages,
until sexual maturation. Fecundity and egg quality of each female
will be related to viability. The parental identity of offspring
will be ascertained using DNA microsatellite markers, which make
it possible to link individual fish, sampled at any stage in their
lifespan, to their parents. The influence of the male cod will
be standardised by using elder males in both groups. The investigation
will improve our understanding of the relative importance of individual
genetic variation, compared to maternal effects (first-time vs.
elder female spawners), on the growth and survival of cod in the
wild and in aquaculture. If the maternal effect is important,
this information will have significant implications for fishery
management. We will examine the demographic structure of selected
European cod stocks, in particular sexual differences in age,
size and maturity in the spawning stock, by analysing data sets
that extend back several decades in history. This information
will be compared with our experimental results, to reveal how
the composition of the spawning stock affects recruitment.
Institute of Marine Research
||Gary R. CARVALHO
The University of Hull
Tel.: +44 1482 465540
Fax: +44 1482 465458
Institut für Meereskunde an der Universitaet Kiel
Tel.: +49 43 15973910
Fax: +49 43 1565876
Tel.: +45 33963200
Fax: +45 33963260