Spatial and temporal trends in condition of Atlantic cod Gadus morhua on the Icelandic shelf

Abstract

Interannual (1993Interannual ( to 2006, spatial and bathymetric trends in the hepatosomatic index (H) and relative body condition index (Kr) of Atlantic cod Gadus morhua in Icelandic waters were investigated from data collected during annual spring (March) groundfish surveys. Individual stomach content data were analysed to assess the relationship between condition and consumption of capelin Mallotus villosus. Liver condition was found to vary with region and depth, tending to be highest in deeper water and in the northern and eastern regions; where temperatures were relatively cold and capelin consumption relatively high. A continuous decline in condition of cod in waters off the east coast was observed throughout the study period. Mature cod were found to be in significantly better condition than immature cod of the same age, and mature females were in better condition than mature males. Different patterns emerged from the 2 condition indices; little variation in Kr was observed whereas H was found to be a dynamic index of condition, suggesting that these metrics are not equivalent measures of cod bioenergetic condition.

Impact of environmental temperature on Atlantic cod Gadus morhua energy allocation to growth, condition and reproduction

“…Appetite may actually be suppressed at low temperature, leading to a decrease in condition (Jobling 1988, Morgan 1992. However, other studies have found little or no effect of temperature on condition (Yaragina & Marshall 2000, Yoneda & Wright 2005a, Pardoe et al 2008. Changes in the abundance and type of prey available with varying temperature can also influence condition.…”

Temporal trends in probabilistic maturation reaction norms and growth of Atlantic cod (Gadus morhua) on the Icelandic shelf

“…However, mature cod have been found to have higher liver condition than immature cod (Eliassen and Vahl 1982b;Vitale et al 2006;Pardoe et al 2008), suggesting that better condition may be the consequence, rather than cause, of maturation (Rijnsdorp 1990). If this is the case, it could mean the false interpretation of a positive effect of condition on maturation probability (Grift et al 2007), and should therefore be considered in future experimental investigations.…”

“…However, it is unlikely that changes in condition are responsible for the overall downward trend in maturation, although it is feasible that short-term variation in condition (Pardoe et al 2008) may have contributed to the observed variability in Lp50s. In four previous PMRN studies, of plaice (Pleuronectes platessa, Grift et al 2007), sole (Solea solea, Mollet et al 2007), and Atlantic cod in the Baltic (Vainikka et al 2009) and off Newfoundland (Baulier et al 2006), inclusion of condition as a third explanatory variable of maturation probability did not alter the conclusion of a decreasing temporal trend in the PMRN midpoints.…”

“…Phenotypic (Marteinsdóttir and Begg 2002;Jónsdóttir et al 2006;Pardoe et al 2008), and more recently genetic (Pampoulie et al 2006) and behavioural (Pálsson and Thorsteinsson 2003;Pampoulie et al 2008;V. Thorsteinsson, MRI, Skúlagata 4, 121 Reykjavik, Iceland, unpublished data), structure within the Icelandic cod stock has been detected.…”

Seasonal and spatial variations in prey utilization and condition of a piscivorous flatfish Paralichthys olivaceus

“…To examine seasonal and spatial variations in feeding activity and nutritional status of Japanese flounder, we determined the stomach content index (SCI), hepatosomatic index (H), and relative condition factor (Kr) (Pardoe et al 2008) in 4 size classes (20.0-29.9, 30.0-39.9, 40.0-49.9, and ≥50.0 cm TL) as follows:…”