The influence of temperature on advective loss of Atlantic cod (Gadus morhua) eggs from the inshore environment

Abstract

We use a simple model of temperature‐dependent egg development and mortality to develop several hypotheses concerning the effect of temperature on the occurrence of eggs of Atlantic cod, Gadus morhua, in Placentia Bay, Newfoundland. Predictions from this exploratory model were tested through a series of synoptic ichthyoplankton surveys throughout spawning and postspawning periods during 1997 and 1998. Although several egg mortality relationships were explored through the simulation, a constant mortality rate best represented the pattern observed in the two years of data. Peaks in late stage egg densities occurred in August of both 1997 and 1998 and were apparently decoupled from egg production peaks in April. We observed a decrease in mortality and the distance dispersed during egg development with increases in water temperature. We suggest that the effects of predation are small relative to the advective effects within this system, and that the interaction between advection and temperature‐dependent vital rates of eggs may have dramatic consequences for coastal retention of propagules produced by inshore spawning events.

Egg development rates for use in egg production methods (EPMs) and beyond

“…the use of Paulik diagrams utilizing modeled data (Nash, 1998) for Irish Sea plaice, egg drift modeling such as for plaice in the North Sea (van der Veer et al, 1998;Bolle et al, 2009) or Irish Sea (Fox et al, , 2009, haddock in the North Sea (Heath and Gallego, 1998), and cod off Newfoundland (Bradbury et al, 2000). Egg development rates along with particle tracking models and field data have been used to raise hypotheses concerning distribution patterns, mortality rates and retention (Pepin and Helbig, 1997;Bradbury et al, 2001;Knickle and Rose, 2010). Egg development rates have also been used in the determination of spawning or hatch dates ( Van der Veer et al, 2000;Fox et al, 2007) and dispersal patterns of a variety of species (van der Molen et al, 2007).…”

Environmental regulation of individual depth on a cod spawning ground

“…Cod are known to be very sensitive to temperature during the spawning season , when they have a narrow thermal 'window' because of the aerobic demands of large repro ductive organs (Pörtner & Farrell 2008, Kjesbu et al 2010. Temperature also plays a fundamental role in determining the quality of oocytes released (van der Meeren & Ivannikov 2006) and the subsequent survival and growth of eggs and larvae (Otterlei et al 1999, Bradbury et al 2001.…”

“…Fish may therefore adjust their depth to avoid extreme conditions or to select microhabitats with conditions favourable for physiological performance or reproductive success. Temperature has important consequences for oocyte maturation in female cod (Kjesbu et al 2010) and survival and development of gametes and larvae (Otterlei et al 1999, Bradbury et al 2001. Wind-and tidal-driven currents affect both the dispersal of fertilised eggs and larvae (Ottersen & Sundby 1995) and the energetic cost of swimming or maintaining position (Arnold et al 1994).…”

Discrete spatial dynamics in a marine broadcast spawner: Re-evaluating scales of connectivity and habitat associations in Atlantic cod (Gadus morhua L.) in coastal Newfoundland

“…1). The exact location of spawning in Bonavista Bay is likely in the southern portion of the bay based on likely larval drift projections and development times (e.g., Bradbury et al, 2001). …”