Antifreeze Production, Freeze Resistance, and Overwintering of Juvenile Northern Atlantic Cod (Gadus morhua)

Abstract

Four size groups of northern Atlantic cod (Gadus morhua) (juveniles < 15, 15–25, and 26–40 cm and adults > 50 cm) were investigated over a winter cycle for their ability to increase freeze resistance by producing plasma antifreeze glycoproteins. All juveniles had significantly higher plasma antifreeze levels than adults during the winter (January–March) under similar conditions of cycling temperature and ambient photoperiod. Highest winter plasma antifreeze levels and lowest plasma freezing temperatures were consistently found in the 15–25 cm group. Fish length and plasma antifreeze levels were inversely related from January to April, with the exception of the 0 + cod. All juvenile groups developed considerable freeze protection early in the winter cycle before the onset of freezing temperatures. However, the adults were not significantly protected until the end of January, when ambient temperatures had fallen below 0 °C. The 15–25 cm cod were held in three cycling temperature regimes. Induction temperatures for antifreeze production in this size group appeared to be between 2 and 3 °C, as compared with between 1 and 0 °C for the adults. We suggest that these patterns of antifreeze production may have direct bearing on habitat selection and overwintering behaviour of the northern Atlantic cod at different stages of development.

Season and site fidelity determine home range of dispersing and resident juvenile Greenland cod Gadus ogac in a Newfoundland fjord

“…Similar seasonal movements to deep water have been observed in Atlantic cod (Hanson 1996, Comeau et al 2002, Cote et al 2004, Espeland et al 2010. Importantly, however, plasma antifreeze levels in juvenile cod are significantly higher than in adults during winter conditions (Kao & Fletcher 1988, Goddard et al 1992. Consequently, when larger pre dators leave the area for warmer, deeper waters, age 1 juveniles likely can exploit the newly vacated areas that were previously dangerous for them in the pre-winter season.…”

“…This period correlates with changes in the distribution of several fishes, including cod, and their predators in our study area (e.g. Cote et al 2003Cote et al , 2008, many of which move to deeper water to avoid sub-zero temperatures and ice crystals (Goddard et al 1992). Changes in ice distribution, presence of super-cooled water, and sudden autumn temperature drops are known to kill both adult (Hoag 2003) and juvenile cod (R. S. Gregory unpubl.…”

“…are thought to have more limited distributions, with movements restricted within home ranges of a few hundred to thousands of square metres (Tupper & Boutilier 1995, Laurel et al 2004). Furthermore, both juvenile Atlantic and Greenland cod can produce plasma antifreeze glycoproteins (Morin et al 1991, Goddard et al 1992 at levels double those seen in older conspecifics (Kao & Fletcher 1988). These glycoproteins are an adaptation to overwintering environments (Goddard et al 1999), potentially allowing age 1 juveniles to remain in cooler, shallower waters than their predators during the winter season.…”

Timing of cod reproduction: interannual variability and the influence of temperature

“…1985,1987,1989,1990; Table 1). On the basis of these experiments and on Bull's (1936Bull's ( , 1951 demonstration that cod can distinguish temperatures differing by less than 0.1 "C, Goddard et al (1992) hypothesized that the high sensitivity of cod to the thermal characteristics of their surroundings should enable them to detect and, where the option exists (e.g. in 3Ps but perhaps to a lesser extent in 3L), avoid very cold water.…”

“…Given that it may take up to 2 mo for plasma ionic concentrations to attain a new equilibrium (Fletcher 1981, Fletcher et al 1987, the physiological costs of migration lnto sub-zero temperature water may be prohibitive. The limited ability of adult cod to prevent freezing at temperatures less than -1.2"C (Goddard et al 1992) should also favour avoidance of the extremely low temperatures that dominate St. Pierre Bank in some years ( e . g .…”