Population biology of northern shortfin squid (Illex illecebrosus) in the Northwest Atlantic Ocean and initial documentation of a spawning area
Abstract Growth, maturity, and age structure of the northern shortfin squid (Illex illecebrosus) population were characterized from samples collected during a stratified, random bottom-trawl survey conducted in May 2000. The survey was conducted on the continental shelf of the east coast of the US a...
| Published in: | ICES Journal of Marine Science |
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| Main Author: | |
| Format: | Article in Journal/Newspaper |
| Language: | English |
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Oxford University Press (OUP)
2004
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| Online Access: | http://dx.doi.org/10.1016/j.icesjms.2003.10.010 http://academic.oup.com/icesjms/article-pdf/61/2/252/29158879/61-2-252.pdf |
| Summary: | Abstract Growth, maturity, and age structure of the northern shortfin squid (Illex illecebrosus) population were characterized from samples collected during a stratified, random bottom-trawl survey conducted in May 2000. The survey was conducted on the continental shelf of the east coast of the US and utilized a commercial squid fishing vessel and standardized sampling protocols and gear. Statolith increment counts of 391 individuals, representing the full maturity spectrum from juveniles to mated females (34–250 mm), ranged in age from 69 to 215 d. Substantial variability in the precision of individual age estimates was encountered. The population consisted of a predominant winter cohort of maturing and mature squid (hatched during October–February, with a peak in January) and a spring cohort of juveniles (hatched during February and March, with a peak in March). Recruitment patterns to northern and southern fishing grounds are discussed. The first evidence of a spawning area, located on the continental shelf in the Mid-Atlantic Bight, is presented. Growth in length and weight was best described by a Gompertz model and a power model, respectively. The age range of mated females (115–215 d) indicated a shorter lifespan than expected based on maturity and age information for Newfoundland squid. A latitudinal cline in female size-at-maturity was evident, whereby maturity stages of squid in the southern part of the survey area were more advanced than those in the northern part. Also, females from US waters reach maturity and spawn at smaller sizes and younger ages than females from Newfoundland waters. The results suggest that females from the Mid-Atlantic Bight may exhibit faster rates of growth and maturation, and possibly a shorter lifespan, than their Newfoundland counterparts. |
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