Migratory behaviour and range in Atlantic cod: inference from a century of tagging

Abstract

A century of tagging experiments on 174 Atlantic cod (Gadus morhua) groups is reviewed and the frequency and spatial distribution of four migratory behaviours documented. Of all cod groups, 41% were categorized as sedentary, 18% as accurate homers, 20% as inaccurate homers and 20% as dispersers (ranging over large areas without recognizable return migrations). All behaviours occurred over the full spatial range of cod. Coastal groups did not differ significantly from offshore (shelf) groups in the relative frequency of migratory behaviours. However, the north-east Atlantic had more sedentary and accurate homing groups than did the north-west Atlantic, which had more dispersing groups. Overall, sedentary cod groups had lower maximum historical biomass than did other groups, confirming that migration/dispersal begets abundance. Maximum historical biomass was strongly related to the area occupied [log (biomass, tonnes)] ¼ 1.58 log (range, km 2 ) + 1.529; r 2 ¼ 0.9), irrespective of migratory type (for 23 major groups a total of 22 million tonnes over 3.3 million km 2 with an average density of 7 tonnes km )2 ). Historical densities were not related to area occupied, although all large groups exhibited high densities (10-12 tonnes km )2 ; smaller groups had a wide range of density). The four migratory strategies in cod enable entrainment by diverse physical, oceanographic and biological ecosystem properties, and is key to cod success in the North Atlantic.

Fine-scale spatial and temporal genetic structure of Atlantic cod off the Atlantic coast of the USA

“…The spring spawning fish (NSC of our study) do not appear to undertake extensive migrations, but have limited movements along the GOM coast, exhibit spawning site fidelity and have been characterized as 'sedentary residents' (after Robichaud & Rose 2004, Howell et al 2008, Tallack 2009). Cod comprising the SC appear to display more extensive adult movements than do those of the NSC.…”

“…Mar Ecol Prog Ser 410: [177][178][179][180][181][182][183][184][185][186][187][188][189][190][191][192][193][194][195] 2010 the importance of processes that limit dispersal and promote self-replenishment of local populations, such as sedentary adult life history strategies (Robichaud & Rose 2004, Howell et al 2008, spawning site fidelity (Taggart 1997), natal homing (Thorrold et al 2001, Svedäng et al 2007), egg and larval retention (Jones et al 1999, 2005, Bradbury et al 2008) and local adaptation (McIntyre & Hutchings 2003, Conover et al 2006, Hutchings et al 2007). The implications of such fine-scale population structure are important for effective management (Palumbi 2003, Bradbury et al 2008, Reiss et al 2009).…”

“…Hutchinson et al 2001, Knutsen et al 2003, Nielsen et al 2003, Jorde et al 2007) and in Canadian waters (Ruzzante et al 1996b, 1998, Beacham et al 2002, it has received much less attention in US waters (Lage et al 2004, Wirgin et al 2007). Much of the genetic diversity in this species may reside in smaller sedentary populations that may be particularly vulnerable to overharvest (Robichaud & Rose 2004).Atlantic cod in US waters are currently managed by a 2-stock model consisting of (1) a Gulf of Maine (GOM) stock and (2) a stock encompassing Georges Bank and areas southward, from southern New England to the mid-Atlantic coast. Recent evidence, including the results of tagging studies, suggests that cod movements do not conform to the 2-stock model (Tallack 2009).…”

Link between vertical and horizontal movement patterns of cod in the North Sea

“…There is great concern over the decline in stock sizes for the cod Gadus morhua, particularly in the North Sea and the Grand Banks in the last 20 yr (Myers et al 1997, Christensen et al 2003, Horwood et al 2006. While the understanding of cod movements is increasing (Turner et al 2002, Robichaud & Rose 2004, Neat et al 2006, Svedäng et al 2007, the development of a mechanistic understanding of these movements may allow the availability of cod fishing potential at different spatial and temporal scales (O'Brien et al 2000). Similarly, information on cod depth utilisation (e.g.…”

Environmental mediation of Atlantic cod on fish community composition: an application of multivariate regression tree analysis to exploited marine ecosystems

“…This is consistent with previous findings that cod behaviour may be influenced by the environment, in that fish tend to show less summer site fidelity in colder periods compared to warmer ones (Ruppert et al 2009). Another factor potentially influencing range changes is abundance, with the expectation of range expansion in some species with increasing abundance (for cod, see Robichaud & Rose 2004). Over the period of our study, there were changes in the abundance of various species throughout the Gulf region.…”