Sub-populations of coastal cod with different behaviour and life-history strategies

Abstract

This study provides evidence of countergradient variations in life-history traits among coastal cod Gadus morhua off the Norwegian coast, suggesting the existence of sub-populations. One-yr-old wild-caught individuals from 70°N were smaller, grew slower, weighed less, and had a lower condition factor (CF) than southern cod from 60°N during the sampling period from June to February. In contrast, both a higher growth potential and an increase in CF were found in northern cod when offspring of northern and southern cod from the same area and of the same age as the wild cod were housed together in a 'common-garden' experiment. The rapid growth in northern cod was achieved by higher success in food competition when given a restricted amount of food. Active feeding behaviour and larger energy allocation to storage tissues, as suggested by the higher increase in condition, represents adaptations to the high-latitude environment for northern cod and countergradient variation. These differences suggest the existence of genetically distinct sub-populations along the Norwegian coast. Development of sub-populations that differ in behaviour and life-history strategies are discussed in relation to mechanisms for local retention of early life stages and local adaptation of older stages. Sub-populations with different life histories may respond differently to fisheries, and attention to this could be beneficial for improving fisheries management.

Spatiotemporal distribution of coastal and oceanic Atlantic cod Gadus morhua sub-groups after escape from a farm

“…Also, Salvanes et al (2004) documented behavioural differences between sub-groups of juvenile cod farmed in common-garden experiments. The lack of difference between NCC and NEAC in the present study might be related to several conditions.…”

Conservation physiology for applied management of marine fish: an overview with perspectives on the role and value of telemetry

“…It is clear that different populations of cod respond differently to temperature and thermal gradients [60][61][62] and, as a population-rich species [63], this population complexity is a key driver in modulating the way that cod populations will respond to environmental change. Integrating this degree of complexity into resource management and climate change models is likely to be a considerable challenge and it may be that simpler but valid generalizations will need to be developed and tested in future field studies.…”

Absence of countergradient and cogradient variation in an oceanic silverside, the California grunion Leuresthes tenuis

“…This is evidenced by the fact that local adaptation is seen in some oceanic species, such as Atlantic cod (Purchase & Brown 2001, Salvanes et al 2004) and turbot . In some of the oceanic species for which adaptation has been observed, it is possible that dispersal is more limited than in other oceanic fishes (Fairbairn 1981, Grant et al 1984, Diakov 1998, Foss et al 1998, Shulman 1998.…”

“…For example, Atlantic cod Gadus morhua, displays CnGV in growth patterns similar to those of estuarine silverside fishes (Salvanes et al 2004). Two flatfish species, turbot and halibut, have also been shown to exhibit CnGV in growth , Jonassen et al 2000, and a reef fish, the neon damselfish, was found to show CnGV in egg size and number (Kokita 2003), although in these species mixing may be more limited compared to other oceanic fishes (Fairbairn 1981, Grant et al 1984, Diakov 1998, Foss et al 1998, Shulman 1998.…”