Life history and ecology of the gadoid resources of the Barents Sea

Bergstad, Odd Aksel; Jørgensen, Terje; Dragesund, Olav

doi:10.1016/0165-7836(87)90037-3

Cited by 245 publications

(179 citation statements)

References 17 publications

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“…Although some energy undoubtedly is lost in this process, the resorption of developing oocytes allows females to recover oocyte energy if nutritional conditions become unfavorable (21). NEAC undertake a long-distance spawning migration (∼800 km each way) (22), starting in early December (23). Like other animal migrations (24)(25)(26), this migration incurs considerable energetic costs (27).…”

Section: Discussionmentioning

confidence: 99%

Frequent skipped spawning in the world’s largest cod population

Skjæraasen

Nash

Korsbrekke

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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Life-history theory suggests that animals may skip reproductive events after initial maturation to maximize lifetime fitness. In iteroparous teleosts, verifying past spawning history is particularly difficult; the degree of skipped spawning at the population level therefore remains unknown. We unequivocally show frequent skipped spawning in Northeast Arctic cod (NEAC) in a massive field and laboratory effort from 2006 to 2008. This was verified by postovulatory follicles in temporarily arrested ovaries close to the putative spawning period. At the population level, "skippers" were estimated to be approximately equally abundant as spawning females in 2008, constituting ∼24% of the females 60-100 cm. These females never truly started vitellogenesis and principally remained on the feeding grounds when spawners migrated southward, avoiding any migration costs. The proximate cause of skipping seems to be insufficient energy to initiate oocyte development, indicating that skipped spawning may partly be a density-dependent response important in population regulation. Our data also indicate more skipping among smaller females and potential tradeoffs between current and future reproductive effort. We propose that skipped spawning is an integral life-history component for NEAC, likely varying annually, and it could therefore be an underlying factor causing some of the currently unexplained large NEAC recruitment variation. The same may hold for other teleosts.codfish | population dynamics | reproductive biology | total egg production | stock reproductive potential P opulation demography changes according to reproduction and mortality. In high latitude marine ectotherms, including teleosts, survival of the youngest age classes varies substantially, resulting in large fluctuations in population size (1). Historic spawning stock biomass (SSB) is used to forecast future fish recruitment, although the amount of unexplained variation indicates that SSB may not accurately reflect offspring production (2, 3). One factor that could significantly impact egg production is skipped spawning-the failure of iteroparous spawners to use each spawning opportunity after sexual maturity sensu (4). For most teleosts this phenomenon and its impact on population demography has received scant attention, but theoretical models indicate that up to 30% of the mature individuals may skip spawning and that it is an adaptive strategy optimizing lifetime fitness (5). To date, skipped spawning has been documented in more than 30 species (4, 6), including freshwater (7), marine (8), and anadromous teleosts (9). It has been documented for fish with both indeterminate and determinate fecundity and sequential hermaphrodites (6) and in species with as diverse life histories as the European horse mackerel Trachurus trachurus (10) and the orange roughy Hoplostethus atlanticus (8). Given the difficulty in conclusively establishing past spawning, reports of skipped spawning in teleosts are commonly anecdotal (4).The major process of energy transfer and oocyte gr...

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Section: Discussionmentioning

confidence: 99%

Frequent skipped spawning in the world’s largest cod population

Skjæraasen

Nash

Korsbrekke

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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“…Coastal habitats, where young cod are primarily distributed (Bergstad et al 1987, Sinclair 1992, Anderson & Rose 2001, serve as important nurseries (Godø 1984). Within these zones it appears that juveniles show a general preference for structurally complex substrates, although greater flexibility is demonstrated as they age.…”

Section: Discussionmentioning

confidence: 99%

“…In the wild, juvenile Atlantic cod utilize shallow coastal waters as nurseries (Templeman & Fleming 1965, Riley & Parnell 1984, Bergstad et al 1987, Sinclair 1992, Pihl & Ulmestrand 1993, Dalley & Anderson 1995, Anderson & Rose 2001. As juveniles age, they move to progressively deeper water until, at 3 to 4 yr, they join adult conspecifics (Templeman 1974).…”

Section: Introductionmentioning

confidence: 99%

Microhabitat use of juvenile Atlantic cod in a coastal area of Newfoundland determined by 2D telemetry

Côté¹,

Ollerhead²,

Scruton³

et al. 2003

Mar. Ecol. Prog. Ser.

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A location-finding acoustic telemetry system (resolution ±1 m) was used to map ocean substrates and to continuously monitor the habitat associations (substrate, water temperature, and depth) of 58 Age 2 to 3 juvenile Atlantic cod Gadus morhua from 11 August to 20 December 1999. Substrate use was studied in 2 stages to determine if it differed from the pattern expected given an absence of selectivity (substrate use proportional to substrate availability). The first level compared the proportions of substrate in the study-area home ranges of Atlantic cod to those of the entire study site. The second assessed if the time spent over specific substrates was proportional to the substrate availability within the study-area home ranges. Boulder substrate was incorporated into the home ranges of juvenile Atlantic cod more than would be expected given its availability within the study area. Kelp substrates were included in these home ranges less than expected while sand and gravel were used in proportion to availability. Time spent over substrates within study-area home ranges varied over the diel and seasonal periods. Within study-area home ranges, juvenile cod occurred in boulder substrates at levels greater than or equal to availability. Conversely, the proportion of time spent over open substrates (e.g. sand and gravel) was either less than or not different from those of substrate availability. Kelp substrates were used less than expected in August and December and more than expected in September and October. Over the diel period, it was found that nocturnally, associations with structure diminished except during September and December when boulder habitats were still used to a greater degree. Unlike younger conspecifics, Age 2 to 3 cod in Buckley Cove were not strictly associated with structurally complex substrates, which suggests that these fish experience less vunerability to predation. Also, unlike younger conspecifics, the distribution of Age 2 to 3 cod did not shift inshore nocturnally and therefore they did not benefit metabolically by moving through the thermocline that existed from August to mid-November. This study indicates that substrate use by juvenile cod is dynamic and the strength of associations with structural complexity varies over diel and seasonal temporal scales.

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“…The NCC stock, much smaller in size, has spawning grounds in part overlapping with those of NEAC, but also spawns at longknown local spawning sites within fjords (Jakobsen 1987). Whereas the NEAC larvae and 0-group juveniles drift northeastward with coastal currents and eventually up into their nursery grounds in the Barents Sea (Bergstad et al 1987), NCC tend to remain within the fjords where they were spawned or at least show a high degree of homing to their own fjord (Skjaeraasen et al 2011).…”

Section: Introductionmentioning

confidence: 99%

“…Rollefsen 1934, Bergstad et al 1987). They differ not only in migratory mode but also in settling regimes for 0-group juveniles: NEAC juveniles settle in deep water, and NCC juveniles settle in shallow water (Fevolden et al 2012).…”

Section: Introductionmentioning

confidence: 99%