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Status of Fishery Resources off the Northeastern US
NEFSC - Resource Evaluation and Assessment Division


December 2006

Northern shortfin squid

Northern shortfin squid (Illex illecebrosus)

by Lisa Hendrickson

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Figure 30.1 Statistical areas used to define the Illex squid stock.
Figure 30.1 Statistical Areas Used
Distribution, Biology and Management

The northern shortfin squid, Illex illecebrosus, is a highly migratory, transboundary species that is distributed in the Northwest Atlantic Ocean from the Florida Straits to Newfoundland (Dawe and Hendrickson 1998). The northern component of the stock, extending from Newfoundland to the southern Scotian Shelf, is assessed annually and managed by the Northwest Atlantic Fisheries Organization (NAFO) based on a total allowable catch (TAC). The southern and U.S. stock component, extending from the Gulf of Maine to Florida (Figure 30.1), has been managed since 1977 by the Mid-Atlantic Fishery Management Council (MAFMC), based on an annual TAC, under the provisions of the Atlantic Mackerel, Squid, and Butterfish Fishery Management Plan (FMP).

I. illecebrosus live for less than one year, experiences high natural mortality rates, and exhibit a protracted spawning season whereby overlapping “microcohorts” enter the population throughout the year over a wide geographic area and exhibit variable growth rates. Age estimation, accomplished by counting daily growth increments in the statoliths, has been validated for I. illecebrosus (Dawe et al. 1985; Hurley et al. 1985). Back-calculated hatch dates from statolith-based aging studies indicate that spawning occurs throughout most of the year (Dawe and Beck 1997; Hendrickson 2004). The only confirmed spawning area is located in the Mid-Atlantic Bight where the winter cohort spawns during late May (Hendrickson 2004). Spawning may also occur offshore in the Gulf Stream/Slope Water frontal zone, where Illex sp. paralarvae have been collected (O’Dor and Balch 1985; Rowell et al. 1985), and south of Cape Hatteras, during winter, where Illex sp. hatchlings have been collected (Dawe and Beck 1985). The lifespan of the winter cohort in U.S. waters ranges from 115 to 215 days (Hendrickson 2004). The species is semelparous and fishing mortality and spawning mortality occur simultaneously on the U.S. shelf (Hendrickson and Hart 2006). The species inhabits offshore shelf and slope waters primarily during spring through autumn (Hendrickson and Holmes 2004). Species distribution and abundance are strongly influenced by oceanographic factors (Dawe and Warren 1993; Dawe et al. In Press). Annual survey indices of relative abundance and biomass and average body size suggest that the stock has experienced low and high productivity periods (Hendrickson and Showell 2006; NEFSC 2006). The information provided herein reflects the results of the most recent peer-reviewed assessment of the U.S. component of the I. illecebrosus stock

The Fishery

The onset and duration of the Illex fisheries reflect the timing of squid migrations through the fishing grounds. During summer through fall, a bottom trawl fishery occurs on the U.S. shelf, primarily in the Mid-Atlantic Bight, and an inshore jig fishery occurs in Newfoundland waters. Prior to 2000, Illex was also caught on the Scotian Shelf in an international mixed-trawl fishery for squid, argentine and silver hake (Hendrickson and Showell 2006). Total stock landings increased rapidly during the 1970s, from 1,600 mt in 1969 to a peak of 179,300 mt in 1979, and were mostly from the northern stock component (Figure 30.2 [Fig 30.2 Data]). After reaching a peak of 162,100 mt in 1979, landings from the northern stock component declined rapidly to 400 mt in 1983 and have since remained at low levels. From 1982 onwards, landings from the U.S. domestic fishery have comprised the majority of the total stock landings and U.S. harvests have ranged between 2,800 mt and 31,500 mt.

During 1968-1982, U.S. EEZ landings of I. illecebrosus were taken primarily by international fleets and landings reached a peak of 24,900 mt in 1976 (Figure 30.3 [Fig 30.3 Data]).There has been no fishing allowed in U.S. waters by international fleets since 1987. Since 1982, U.S. EEZ landings have been taken primarily by the domestic fleet. Most domestic fishery landings are taken during June September, with a peak in July, by vessels using small-mesh bottom trawls fishing near the edge of the continental shelf. U.S. landings increased from 2,000 mt in 1988 to 18,400 mt in 1994. Landings of 23,600 mt were taken in 1998 (Table 30.1) and resulted in a fishery closure because the TAC (19,000 mt) was exceeded. After 1998, landings declined rapidly to 2,700 mt in 2002. In 2004, landings increased to a record high of 26,100 mt, but the fishery was closed again because the quota (24,000 mt) was surpassed. Landings in 2005 (12,000 mt) were less than half of the 2004 landings.

Illex discards occur in the offshore Loligo fishery during November through April (NEFSC 2006). Annual discards from the Illex and Loligo fisheries combined have ranged between 0.5% and 6.0% of the annual Illex landings by weight. Annual discards were highest during 1998 and 2004 when Illex landings were also highest.

Figure 30.2.  Commercial landings (000's mt) of Illex illecebrosus during 1953-2005.
Figure 30.2

Figure 30.3 Commercial landings (000's mt) of Illex illecebrosus in subareas 5 & 6, 1963-2005.
Figure 30.3

Figure 30.4  Indices of relative abundance (stratified mean number per tow) and biomass (stratified mean kg per tow) of Illex illecebrosus based on NEFSC bottom trawl surveys, 1967-2005.
Figure 30.4

Research Vessel Survey Indices

NEFSC research bottom trawl surveys occur during the annual Illex spring inshore migration onto the shelf and also during the autumn offshore migration (Hendrickson 2004). An unknown fraction of the stock resides beyond the area sampled in these surveys.

During spring surveys, Illex are collected in low numbers and at fewer stations than in the autumn surveys. However, the autumn survey occurs near the end of the fishing season, and therefore, autumn survey indices may represent indices of spawner escapement.

Autumn survey indices indicate that periods of high relative abundance occurred during 1976-1981 and 1987-1990 (Figure 30.4 [Fig 30.4 Data]). An intermediate level of abundance occurred during 1991-1998. The survey indices increased after 1999 and attained a record high in 2003, but declined sharply in 2004 to the level observed in 2002. In 2005, survey indices increased slightly. The magnitude of the autumn relative abundance index is not always related to the magnitude of the U.S landings during the same year (e.g. high landings occurred in 1998 and 2004, but relative abundance was high in 1998 and low in 2004). Large interannual fluctuations in autumn research survey indices are partially attributable to the fact that the survey occurs near the end of the fishing season and that squid distribution is affected by oceanographic conditions (Brodziak and Hendrickson 1999).

Assessment Results

I. illecebrosus was last assessed in November 2005 at SAW 42 (NEFSC 2006). An in-season stock assessment model was developed but the results were considered preliminary because seasonal data were needed to further test the model. As a result, stock status could not be determined because estimates of fishing mortality and stock biomass were not available.

Biological Reference Points

Amendment 8 (MAFMC 1998) of the FMP specifies BMSY as 39,300 mt, MSY as 24,000 mt, and FMSY as 1.22 per year (Table 30.2). However, these reference points were derived from a biomass dynamics model that does not account for the species semelparous life history or adequate spawning escapement, and therefore, should be treated with caution.


It was not possible to evaluate stock status in 2004 because reliable estimates of stock biomass and fishing mortality were not available (NEFSC 2006). Post-fishery, autumn relative abundance indices for Illex reached a record high in 2003, but declined sharply in 2004 and returned to the 2002 level. The record-high survey index was followed by the highest level of landings on record in 2004, 26,000 mt, but landings subsequently declined to 12,000 mt in 2005. Fishing effort in 2004 was twice as high as in 2003.

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Table 30.1 Recreational and commercial landings of Illex illecebrosus (thousand metric tons).

Category 1986-95 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005
 U.S. Recreational - - - - - - - - - - -
       United States 11.7 17.0 13.6 23.6 7.4 9.0 4.0 2.8 6.4 26.1 12.0
       Canada - - - - - - - - - - -
       Other - - - - - - - - - - -
 Total U.S. EEZ1 11.7 17.0 13.6 23.6 7.4 9.0 4.0 2.8 6.4 26.1 12.0
 NAFO Subareas 3 + 4  0.1  8.7 15.6  1.9 0.3 0.4 1.1 0.3 1.1  2.3  0.6
 Total Nominal Catch 11.8 25.7 29.2 25.5 7.7 9.4 4.1 3.0 7.5 28.4 12.6
 1Does not include landings reported as unidentified squid species


Table 30.2 MSY-based reference points for the U.S. component of the Illex illecebrosus stock.

 MSY-based Reference Points
 MSY = 24,000 mt
 BMSY = 39,300 mt
 FMSY = 1.22 per yr (based on a lifespan of 8 months)



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For further information

Brodziak, J.K.T. and L.C. Hendrickson. 1999. An analysis of environmental effects on survey catches of squids Loligo pealei and Illex illecebrosus in the northwest Atlantic. Fish. Bull. 97: 9-24.

Dawe, E. G., and Beck, P. C. 1985. Distribution of size of juvenile short-finned squid (Illex illecebrosus) (Mollusca-Cephalopoda) south of Newfoundland during winter. Vie et Milieu, 35: 139-147.

Dawe E. G., and P. C. Beck. 1997. Population structure, growth, and sexual maturation of short finned squid (Illex illecebrosis) at Newfoundland. Can. J. Fish. Aquat. Sci. 54:137 146.

Dawe, E. G., and Warren, W. G. 1993. Recruitment of short finned squid in the Northwest Atlantic Ocean and some environmental relationships. J. Ceph. Biol., 2: 1 21.

Dawe, E. G., and L. C. Hendrickson. 1998. A review of the biology, population dynamics and exploitation of shortfin squid in the northwest Atlantic Ocean in relation to assessment and management of the resource. NAFO SCR Doc. 98/59.

Dawe, E.G., R.K. O’Dor, P.H. Odense, and G.V. Hurley. 1985. Validation and application of an ageing technique for short-finned squid (Illex illecebrosus). J. Northwest Atl. Fish. Sci. 6: 107-116.

Dawe, E. G., L. C. Hendrickson, E. B. Colburne, K. F. Drinkwater, and M. A. Showell. In Press. Ocean climate effects on the relative abundance of short-finned (Illex illecebrosus) and long-finned (Loligo pealeii) squid in the Northwest Atlantic Ocean. Fish. Oceanog.

Hendrickson, L.C. 2004. Population biology of northern shortfin squid (Illex illecebrosus) in the northwest Atlantic Ocean and initial documentation of a spawning site in the Mid-Atlantic Bight (USA). ICES J. Mar. Sci. 61: 252-266.

Hendrickson, L.C. and D. R. Hart. 2006. An age-based cohort model for estimating the spawning mortality of semelparous cephalopods with an application to per-recruit calculations for the northern shortfin squid, Illex illecebrosus. Fish. Res. 78: 4-13.

Hendrickson, L. C. and E. M. Holmes. 2004. Essential fish habitat source document: northern shortfin squid, Illex illecebrosus, life history and habitat characteristics, Second Edition. NOAA Tech. Memo. NMFS-NE-191. 36 p.

Hendrickson, L.C. and M.A. Showell. 2006. Assessment of northern shortfin squid (Illex illecebrosus) in Subareas 3+4 for 2005. NAFO SCR Doc. 06/46, Serial No. N5271. 16 p.

Hurley, G.V., P. Odense, R.K. O'Dor, and E.G. Dawe. 1985. Strontium labelling for verifying daily growth increments in the statoliths of the short-finned squid (Illex illecebrosus). Can. J. Fish. Aquat. Sci. 42:380-383.

Mid-Atlantic Fishery Management Council (MAFMC). 1998. Amendment 8 to the Atlantic mackerel, squid, and butterfish management plan. Dover, DE. 351 p. plus appendices.

Northeast Fisheries Science Center (NEFSC). 2006. 42nd Northeast Regional Stock Assessment Workshop (42nd SAW) stock assessment report, part A: silver hake, Atlantic mackerel, and northern shortfin squid. Northeast Fish. Sci. Cent. Ref. Doc. 06-09a, 284 p. http://www.nefsc.noaa.gov/nefsc/publications/crd/crd0609/

O’Dor, R.K. and N. Balch. 1985. Properties of Illex illecebrosus egg masses potentially influencing larval oceanographic distribution. Northwest Atl. Fish. Organ. (NAFO) Sci. Counc. Stud. 9: 69-76.

Roper, C.F.E., Lu, C.C., and Vecchione, M. 1998. A revision of the systematics and distribution of Illex species (Cephalopoda: Ommastrephidae)I. In Systematics and Biogeography of Cephalopods, pp. 405-423. Ed. by N.A. Voss, M. Vecchione, R.B. Toll and M.J. Sweeney. Smithsonian Contributions to Zoology, No. 586.

Rowell, T.W., R.W. Trites, and E.G. Dawe. 1985. Distribution of short-finned squid (Illex illecebrosus) larvae and juveniles in relation to the Gulf Stream frontal zone between Florida and Cape Hatteras. Northwest Atl. Fish. Organ. (NAFO) Sci. Counc. Stud. 9: 77-92.

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