Comparative effects of temperature on rates of development and survival of eggs and yolk-sac larvae of Arctic cod (Boreogadus saida) and walleye pollock (Gadus chalcogrammus)

Abstract

Changes in Arctic fish assemblages resulting from climate change will likely be determined by the differential thermal response of key species during their early life history. In this study, we incubated multiple batches of eggs and larvae of two ecologically important gadids co-occurring at the Pacific–Arctic interface, Arctic cod (Boreogadus saida) and walleye pollock (Gadus chalcogrammus). Fertilized egg batches (n = 11 Arctic cod; n = 6 walleye pollock) were collected in the late winter/early spring from laboratory broodstock held under simulated seasonal environmental conditions. Image and lipid analyses indicated that Arctic cod eggs and larvae were ∼25–35% larger than walleye pollock and had nearly 3–6× more energetic reserves. Two batches of eggs from each species were incubated in replicated containers (n = 3/batch/temperature) at −0.4, 1.2, 2.5, 3.8, 5.0, 9.0, and 12.0°C for Arctic cod and −0.8, 0.3, 2.2, 4.5, 9.0, and 12.0°C for walleye pollock. Both species had very similar low thermal tolerance, but Arctic cod were much more sensitive to higher thermal stress in terms of hatch success and size-at-hatch. For example, Arctic cod hatch success declined precipitously at temperatures above 3.5°C yet remained above 50% in walleye pollock at 9°C. Arctic cod also had significantly longer development times, such that embryos could survive for ∼4 months at temperatures <0°C from the time of spawning to first-feeding. Collectively, these results indicate Arctic cod have a much smaller thermal window for survival, but can survive for longer periods in the absence of food than walleye pollock at cold temperatures. These temperature-dependent rates will be useful in the development of population forecasts and biophysical transport models for these species in the northern Bering, Chukchi, and Beaufort seas.

Contribution of walleye pollock eggs to the Gulf of Alaska food web in spring

“…For the egg weight, we used a mean value of 0.12 mg DW based on Hinckley (1990), who also provided the total range of egg weights as 0.097−0.139 mg DW based on estimates from 1319 walleye pollock eggs (Table S2). Similar values with a mean of 0.117 (0.101−0.125 mg DW) were estimated by Laurel et al (2018). C conv is the DW to carbon ratio of 35.3% (range 29.2−39.6%; Harris et al 1986).…”

Key processes regulating the early life history of Barents Sea polar cod

“…In the wake of the increased attention, climate change has attained in recent years (IPCC 2014(IPCC , 2019, and the increased sea temperatures that have already been observed in the Barents Sea and other arctic areas (Smedsrud et al 2013;ICES 2017ICES , 2018, the fate of polar cod and other true arctic species has become a theme of several research projects and research articles (Christiansen 2017;Kunz et al 2018;Bender et al 2018;Koenker et al 2018;Laurel et al 2018). The motivation for studying polar cod in the climate change context is driven by the fact that this species has a circumpolar distribution and in many of the areas where it occurs, it is the dominant pelagic species (Ajiad et al 2011;Bouchard et al 2017), playing a dominant role in those ecosystems (Lowry and Frost 1981;Bradstreet et al 1986;Orlova et al 2009;Hop and Gjøsaeter 2013;Mueter et al 2016).…”

West Greenland ichthyoplankton and how melting glaciers could allow Arctic cod larvae to survive extreme summer temperatures

“…Temperature-dependent regression models based on incubation experiments (Table 2 of Laurel et al 2018), were used to depict how SST affected Arctic cod eggs and larvae over the hatching season for the four region-years with Arctic cod catches. Disko Bay 2019 was the most extreme case.…”

“…At 2.13 ºC, the mean SST of Disko Bay in May 2019 (Table 3), the hatching success of the eggs was 74 %. According to the temperature-dependent models (Laurel et al 2018), May hatchers were large at hatch (6.28 mm SL), and highly tolerant to starvation with 50 % of the larvae dying within 40 days after hatching if not feeding (Table 3). However, very high SST in June 2019 (4.70 °C), resulted in the successful hatching of only 13 % of the eggs hatch that month ( Table 3).…”

“…Arctic cod is no exception to that rule. Under controlled laboratory conditions, Arctic cod eggs developed normally between -1.5 and 3.0 °C and the hatching success declines drastically above 3.0 °C (Sakurai et al 1998;Laurel et al 2018). Different rearing experiments suggest that the upper thermal limit of the early-stage larvae is around 5 °C.…”