Distribution, Biology and Management

Longfin inshore squid (Loligo pealeii) are distributed primarily in continental shelf waters located between Newfoundland and the Gulf of Venezuela (Cohen 1976; Roper et al. 1984). In the northwest Atlantic Ocean, longfin squid are most abundant in the waters between Georges Bank and Cape Hatteras where the species is commercially exploited. The stock area extends from the Gulf of Maine to Cape Hatteras (Figure 31.1). Distribution varies seasonally. North of Cape Hatteras, squid migrate offshore during late autumn to overwinter in warmer waters along the shelf edge and slope, and then return inshore during the spring where they remain until late autumn (Jacobson 2005). Bottom trawl survey catches of L. pealeii are affected by water temperature, time-of-day, and depth (Serchuk and Rathjen 1974) and the affects vary by body size (Brodziak and Hendrickson 1999; Cadrin and Hatfield 1999). The species lives for about nine months, grows rapidly, and spawns year-round (Brodziak and Macy 1996) with peaks during late spring and autumn. Individuals hatched in summer grow more rapidly than those hatched in winter and males grow faster and attain larger sizes than females (Brodziak and Macy 1996).

Assessment Results

Biological Reference Points

Biological reference points were specified in 1998 (MAFMC 1998) based on recommendations from the Overfishing Definition Review Panel (Applegate et al. 1998) (Table 31.2). The fishing mortality rate threshold is defined as an F_MSY proxy equal to F_max, estimated as 0.36 per month (NEFSC 1996), when the annual stock biomass is greater than the B_MSY proxy of 80,000 mt (Applegate et al. 1998), then decreases linearly to zero at a biomass of 30,000 mt. The target fishing mortality rate is defined as 75% of F_max when stock biomass is greater than B_MSY, then decreases linearly to zero at the biomass threshold of 40,000 mt (50% of B_MSY).

During the 2001 assessment, a quarterly per-recruit model was also run but B_MSY could not be estimated and neither the new F-based reference point estimates nor the existing B_MSY reference point were considered appropriate for stock status determination. Rather, a new F_threshold proxy of 0.31 per quarter, representing the 75^th percentile of the fishing mortality rates during 1987-2000, was used to evaluate stock status with respect to overfishing. During 2000, overfishing was not occurring because F₂₀₀₀ was below the proposed F_threshold of 0.31 and stock status with respect to biomass was unknown because there were no appropriate biomass-based reference points available with which to compare the 2000 biomass estimate (NEFSC 2002b).

Summary

The stock status determination for 2000 is outdated because Loligo is a sub-annual species. During 1999-2002, autumn relative abundance indices were well above the time series average and among the highest levels on record. Thereafter, relative abundance declined and was below average in 2005. Landings generally declined after 1999, and in 2003, reached the lowest level since 1987. The decline is partially due to frequent seasonal closures of the directed fishery, which has also resulted in regulatory discarding of Loligo. After 2003, landings increased and were slightly below the 1987-2004 average in 2005.