Variability in maturity and growth in a heavily exploited stock: cod (Gadus morhua L.) in the Irish Sea

• DOI: 10.1016/j.icesjms.2003.10.005
• Publication Date: 2003-12-22T16:49:35Z
• Authors: M.J Armstrong; H.D Gerritsen; M Allen; W.J McCurdy; J.A.D Peel
• Keywords: Groundfish; Irish sea; Sexual maturity; Stock assessment; Stock (firearms); North sea

Abstract Maturity, sex ratio (proportion female by number) and length-at-age of cod in the Irish Sea were examined using data collected during groundfish surveys spring 1992–2002. Skewed ratios with a predominance males observed survey catches 2- 3-year-old taken on spawning grounds. In contrast, commercial midwater trawl same area had consistently higher ratios, suggesting that mature females have different vertical migration behaviour. Estimates proportion not affected method capture. GLM analysis, factor age explained most variation maturity each sex, whilst length, although significant factor, less than year region (spawning non-spawning grounds). Maturity was variable 2-year-olds, virtually no 1-year-olds all 3-year-olds older irrespective or Population estimates from years' combined, 0.87 0.45 females. areas areas, showed general increase over time throughout area. However, any year, at 2 varied little length reduced only smallest fish (<40 cm) this some years. The coincided rising sea surface temperature (SST) decline recruitment stock biomass high rates fishing mortality. Mean differed between classes, differences being largely established first life. fastest growth apparent very weak classes produced late 1990s when SST relatively high. interrelationships growth, maturity, abundance are examined, changes since earlier studies 1970s investigated.