Life history strategies of the squid,Illex illecebrosus,in the Northwest Atlantic

Abstract

Time series of lllex illecebrosus catch and morphomctric data from the Northwest Atlantic were analysed to describe geographic variability in population structure. The areas studied were NAFO sub-areas 3 to 6, which range from Newfoundland to the northeastern USA shelf. Population components, reflecting seasonal spawning groups, were identified based on analysis of length frequency data. Components 3 and 4 represent two prominent life cycles: the summer spawners and winter spawners respectively. Components 1, 2, and 5 do not represent different life cycles, but result from the capacity to shift between life cycles by prolonging (or shortening) the life span. The presence of up to five components in the southern area illustrates a life history strategy involving protracted spawning and complex population structure. There was clear geographic variability in annual catch, with fluctuations being most extreme in the most northem area. Annual catch levels in al1 areas were significantly correlated with the abundance of the winter-spawning component, as represented by the number of squid within samples which belong to component 4. Population structure in the most northem area was simplest and catch levels therefore were most dependent on the highly migratory winter-spawning component. This leads to greater catch variability in the most northern area than in the other areas. The advantages of good feeding conditions may compensate for the risks associated with long-range migrations, especially recruitment failure. Life history strategies involving migratory and non-migratory population components limit the risk of recruitment failure. The overall resultant life history strategy for Illex illecebrosus is one that ensures survival of the species by stabilizing recruitment in at least one (southern) area through protracted spawning, complex population structure and interaction of spawning components.

Environmental effects on recruitment of short-finned squid (Illex illecebrosus)

“…These scenarios, and the broad-scale interrelationships that support them, are consistent with a general life history strategy proposed for short-finned squid (O'Dor and Coelho, 1993;Coelho et al, 1994), and elaborated upon for squid generally (O'Dor, 1998a(O'Dor, , 1998b. This strategy was based on recognition that temperate squid species, with annual life cycles, cannot maintain genetic diversity and recruitment stability through the co-existence of multiple year classes, as fishes do.…”

“…It may be expected that environmental variation would affect year-class strength for a species whose annual life cycle is so closely related to oceanographic features, especially at Newfoundland where this species is near the northern limit of its distributional range (Mann and Drinkwater, 1994;Coelho et al, 1994). An initial investigation of environmental effects on shortfinned squid recruitment (Dawe and Warren, 1993) utilized simple correlation analysis between an abundance index and three environmental indices.…”

Population biology of northern shortfin squid (Illex illecebrosus) in the Northwest Atlantic Ocean and initial documentation of a spawning area

“…However, juveniles and mature females were not present in these samples. Winter cohorts were considered to be the primary source of recruitment to this fishery based on the seasonal distribution of paralarvae (Lu and Roper, 1979;Dawe and Beck, 1985;Dawe and Warren, 1993), length compositions (Squires, 1967;Coelho et al, 1994), and male maturation data (Mercer, 1973). However, this hypothesis was not confirmed by ageing studies of squid sampled from the Newfoundland fishery during 1982 and 1990 (Dawe and Beck, 1997).…”

Squid stock fluctuations and water temperature: temporal analysis of English Channel Loliginidae

“…The well studied Japanese squid Todarodes pacificus (Okutani 1983) shows abundance and migration patterns that depend on the fluxes of cold and warm currents around Japan (Murata 1989). In the North‐west Atlantic squid Illex illecebrosus , egg development seems to be inhibited below a threshold of 12·5 °C (Coelho et al . 1994).…”