© 2004 by ICES/CIEM International Council for the Exploration of the Sea/Conseil International pour l'Exploration de la Mer
Population biology of northern shortfin squid (Illex illecebrosus) in the Northwest Atlantic Ocean and initial documentation of a spawning area
U.S. National Marine Fisheries Service, Northeast Fisheries Science Center 166 Water Street, Woods Hole, MA 02543, USA
*tel: +1 508 495 2285; fax: +1 508 495 2393. e-mail: Lisa.Hendrickson{at}noaa.gov.
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.
Keywords: age, ageing precision, growth, Illex illecebrosus, maturity, squid, statolith
Received 13 January 2003; accepted 17 October 2003.