Movement patterns of Atlantic cod in Gilbert Bay, Labrador: evidence for bay residency and spawning site fidelity

Abstract

During three consecutive years of observation 23 Atlantic cod (Gadus morhua) were tagged with ultrasonic transmitters as part of two experiments to determine the movement patterns of adult cod in the genetically distinctive population inhabiting Gilbert Bay, Labrador. Individual cod were relocated for periods up to 15 months, indicating year-round residency within the bay despite unimpeded access to the open ocean. The tracking data show that individual cod have a strong homing tendency. In experiment 1 displaced cod returned (homed) to their place of capture in a small arm separated from the rest of the bay by a shallow sill while non-displaced fish remained at their capture site. In experiment 2 some cod remained within 2 km of their capture/release site, a spawning area, while others ranged widely in Gilbert Bay before returning to this site. Whether an individual ranged widely or had more restricted movements was not related to size. Cod exhibited wider ranging movements in the spring and early summer, following spawning, than in the late summer and early autumn. The return of Gilbert Bay cod to specific locations in the inner part of the bay to overwinter and spawn is evidence of one mechanism that could have led to their genetic distinctiveness.

The fish fauna of Gilbert Bay, Labrador: a marine protected area in the Canadian subarctic coastal zone

“…The year-round residency of the Gadus morhua population in Gilbert Bay is well documented (Ruzzante et al, 2000;Green & Wroblewski, 2000;Morris & Green, 2002). We collected both juvenile and adult G. morhua, as would be expected for a self-sustaining, local population (Wroblewski et al, 2005).…”

“…Aboriginal fisheries for Salmo salar Linnaeus, 1758 Atlantic salmon and Salvelinus alpinus (Linnaeus, 1758) Arctic char using gill nets are allowed in some regions of the bay, but landings are restricted to personal consumption. The primary objective of the Gilbert Bay MPA is to protect its resident population of Gadus morhua Linnaeus, 1758 Atlantic cod (Green & Wroblewski, 2000;Morris & Green, 2002). These cod have a reddish or golden-brown colour due to their carotenoid-rich diet of invertebrates (Gosse & Wroblewski, 2004;Wroblewski et al, 2005).…”

“…To date, management planning for the MPA has focused on the 'golden cod of Gilbert Bay', since there exists biological data (Green & Wroblewski, 2000;Morris & Green, 2002) on which to base management decisions. However, the management plan is founded on a broader ecosystem approach, and scientific information on other species which inhabit Gilbert Bay is required.…”

Homing in rocky intertidal fish. Are Lipophrys pholis L. able to perform true navigation?

“…The best-known examples of homing ability are among birds (e.g., homing pigeons, Wiltschko and Wiltschko 2003), but there are also good examples among amphibians (e.g., newts, Phillips and Borland 1994) and reptiles (e.g., sea turtles, Luschi et al 2007;Lohmann et al 2008a, b). Marine fish are no exception, as salmon return to their natal rivers to spawn (Dittman and Quinn 1996;Quinn 2005) and Atlantic cod return to their spawning grounds in the sea (Green and Wroblewski 2000;Rawson and Rose 2000;Robichaud and Rose 2001). However, the long-distance migration of fish makes it difficult to observe homing behavior and attempts to explain the homing orientation of migratory fish that have evoked a great variety of proposals regarding the sensory mechanisms involved (Mitamura et al 2005).…”

Population structure and persistence of Pacific herring following the Great Tohoku earthquake

“…Together, these observations suggest a high degree of natal homing and spawning fidelity, but not necessarily to natal spawning areas (Beacham et al 2008), and some fish do stray to other spawning grounds. Evidence for spawning fidelity in marine fish has been reported in Atlantic cod (Green and Wroblewski 2000;Wright et al 2006;Skjaeraasen et al 2011) even for long distance (Bonanomi et al 2016), North Sea plaice (Pleuronectes platessa) (Hunter et al 2003), and bluefin tuna (Thunnus thynnus thynnus) in the western Atlantic (Nemerson et al 2000). All of our samples were collected in the spawning grounds and almost all fish were mature, suggesting that the stable pattern of gene flow was the result of straying of spawning fish.…”