Management Implications of Sexual Differences in Maturation and Spawning Mortality of Northeast Arctic Cod

There is evidence of earlier maturation in males than in females and indications of higher mortality among mature males than mature females in the Northeast Arctic cod (Gadus morhua L.) stock. Both factors affect the composition of the spawning stock by sex and age. One possibility is that spawning...

Full description

Saved in:
Bibliographic Details
Published in:Journal of Northwest Atlantic fishery science 1999, Vol.25, p.125-131
Main Authors: Jakobsen, T, Ajiad, A
Format: Article
Language:English
Subjects:
Females
Fishing
Fishing mortality
Gadus morhua
Landing statistics
Males
Marine
Marine fishes
Mortality
Polar environments
Reproductive behaviour
Sex
Sex ratio
Sexual maturity
Spawning
Spawning populations
Spawning stock biomass
Year class
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:There is evidence of earlier maturation in males than in females and indications of higher mortality among mature males than mature females in the Northeast Arctic cod (Gadus morhua L.) stock. Both factors affect the composition of the spawning stock by sex and age. One possibility is that spawning mortality is involved. Spawning mortality may occur in both sexes, but observations indicate that it might be higher in males. The possibility of a spawning mortality is investigated by adding spawning mortality in calculations of the history of a year-class to see if this improves the fit with observed sex ratios in commercial landings from the Lofoten spawning fishery. The best fit was obtained for a spawning mortality of about 0.05 on the males. However, the results are not conclusive. Splitting the spawning stock into males and females shows that the earlier maturation in males has a larger impact on the sex ratio in the spawning stock than the spawning mortality rates. Increasing the fishing mortality rates will increase the surplus of male spawners. The results have implications for estimation of biological reference points and the way spawning stock biomass is used in management considerations. Estimation of the female SSB is necessary if maternal effects are to be taken into account.
ISSN:0250-6408
1682-9786
1813-1859
DOI:10.2960/J.v25.a11