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Field l/o r3 11/17/07 11:54 AM Page 131 FIELD ET AL.: JUMBO SQUID TROPHIC INTERACTIONS CalCOFI Rep., Vol. 48, 2007 RANGE EXPANSION AND TROPHIC INTERACTIONS OF THE JUMBO SQUID, DOSIDICUS GIGAS, IN THE CALIFORNIA CURRENT JOHN C. FIELD AND KEN BALTZ A. JASON PHILLIPS NOAA Fisheries Southwest Fishery Science Center Cooperative Institute for Marine Resources Studies 110 Shaffer Road Oregon State University Santa Cruz, California 95060 Hatfield Marine Science Center [email protected] 2030 Marine Science Drive Newport, Oregon 97365 WILLIAM A. WALKER NOAA Fisheries National Marine Mammal Laboratory Alaska Fisheries Science Center 7600 Sand Point Way N.E., Building 4 Seattle, Washington 98115 ABSTRACT than males, with DMLs as large as 100 to 120 cm, cor- Although jumbo squid (Dosidicus gigas) have been oc- responding to weights of 30 to 50 kg (Nigmatullin casional visitors to the California Current over the last et al. 2001). Nigmatullin et al. (2001) described some century, their abundance and distribution increased be- apparent population structure of jumbo squid, with tween 2002 and 2006. We report several time series of individuals growing to a smaller size and maturing ear- jumbo squid relative abundance from commercial and lier in the core of their range in the ETP, and growing recreational fisheries as well as resource surveys and food (and maturing) larger at the poleward fringes of their habits studies. To evaluate the trophic relationships of range, consistent with the observation by O’dor (1992) jumbo squid, we report the results of 428 stomach sam- that squid tend to grow larger and reproduce later in ples collected between 2005 and 2006 at various loca- cooler waters. tions and seasons along the U.S. West Coast. Prey were Gilly et al. (2006) found that while squid spent most identified using hard parts, primarily squid beaks and daylight hours at depths greater than 250 m and foraged otoliths, and prey sizes were estimated where possible. in near-surface waters at night, they often made short- While jumbo squid forage primarily on small midwater term vertical migrations from surface waters to depth and forage fishes, they also prey on adult groundfish such throughout the night. Their results demonstrated a greater as Pacific hake (Merluccius productus), shortbelly rockfish appreciation for the extent of diel movement and the (Sebastes jordani), and other species with semi-pelagic life tolerance of jumbo squid for a wide range of both tem- histories. As their ability to prey on larger items suggests perature and oxygen levels over short time periods. potential impacts on ecosystems, we also consider the Tagging results also demonstrate that jumbo squid are role of jumbo squid in a food web model of the north- capable of migrating up to 30 miles a day for several days ern California Current. in a row (Markaida et al. 2005; Gilly et al. 2006). The usual range of jumbo squid extends from central Chile INTRODUCTION through the coastal and pelagic waters of the ETP, and The jumbo squid (Dosidicus gigas) is one of the largest into the Gulf of California. However, the distribution and most abundant nektonic squid in the epipelagic zone and density of jumbo squid throughout their range are throughout the Eastern Tropical Pacific (ETP). As such, characterized by irregular migratory incursions of large jumbo squid are an important component of subtropi- numbers of squid at the fringes of their habitat in both cal food webs, representing a conduit of energy transfer hemispheres (Nesis 1983; Ehrhardt 1991; Nigmatullin from the mesopelagic food web to higher trophic level et al. 2001; Ibáñanez and Cubillos 2007). tunas, billfish, sharks, and marine mammals (Nesis 1983; Jumbo squid were described as “not uncommon” to Nigmatullin et al. 2001; Olson and Watters 2003). Jumbo the waters of southern and central California by Berry squid also support major fisheries in the Gulf of (1912) and Phillips (1933), and were particularly abun- California, the ETP, and the coastal waters of Peru and dant for several years in the mid 1930s, when they were Chile, although catches are highly variable in space and described as a nuisance to salmon, tuna, rockfish, and time. Like most cephalopods, jumbo squid are charac- recreational charter boat fishermen (Clark and Phillips terized by rapid growth and short life spans. In the Gulf 1936; Croker 1937). There are few records of their pres- of California, growth rates of 1 to 1.5 mm dorsal man- ence in California waters between the late 1930s and tle length (DML) per day were estimated for squid in 1950s (Phillips 1961), although episodic strandings and 50 to 70 cm size classes, consistent with lifespans of 1.5 fisheries occurred sporadically throughout the 1960s and to 2 years (Markaida et al. 2005). There is general con- 1970s (Fitch 1974; Anderson 1978; Nesis 1983; Mearns sensus that females are more abundant and grow larger 1988), and their presence in the Southern California 131 Field l/o r3 11/17/07 11:54 AM Page 132 FIELD ET AL.: JUMBO SQUID TROPHIC INTERACTIONS CalCOFI Rep., Vol. 48, 2007 Bight was episodic throughout most of the 1980s and (A. Preti, NOAA/NMFS/SWFSC, La Jolla, California, 1990s. During the 1997–98 El Niño event, jumbo squid pers. comm.). were observed in substantial numbers off California, as Fisheries resource surveys have provided both quan- well as in coastal waters off of Oregon and Washington titative and qualitative estimates of abundance for many states (Pearcy 2002). In situ video observations taken commercially and ecologically important species rele- from remotely operated vehicle (ROV) surveys from the vant to this study. We compiled data from pelagic mid- Monterey Bay region show that jumbo squid continue water trawl surveys for juvenile groundfish conducted to be present and sporadically abundant since the 1997–98 in May and June off of the central California coast by El Niño, particularly between 2003 and 2006. Their the NOAA Fisheries Southwest Fisheries Science Center presence in the surveys has been associated with declines (SWFSC) since 1983 (Sakuma et al. 2006), and a com- in observations of Pacific hake (Merluccius productus) parable midwater trawl survey conducted by the NOAA (Robison and Zeidberg1). Since 2003, jumbo squid have Fisheries Northwest Fisheries Science Center (NWFSC) been frequently reported in beach strandings, commer- off of Oregon and Southwest Washington between May cial and recreational fisheries, and resource surveys along and November from 2004–06 (Brodeur et al. 2006). the West Coast and through southeast Alaska (Cosgrove Finally, bycatch monitoring data by fisheries observers 2005; Brodeur et al. 2006; Wing 2006). on commercial at-sea catcher-processors targeting Pacific In this study, we report several time series of jumbo hake off of Oregon and Washington, including average squid relative abundance from commercial and recre- weights per haul, are available from 1991 to the present, ational fisheries as well as resource surveys and food habits although jumbo squid were only routinely identified to studies in order to evaluate the trophic relationships of species in 2006. In recent years, catches of squid have jumbo squid along the U.S. West Coast. increased substantially, with hauls of 25 to 75 tons of squid not uncommon, and most large squid hauls were METHODS composed primarily of jumbo squid (V. Wespestad, At- To consider trends in jumbo squid abundance through- Sea Processors Assn., pers. comm.). Consequently, we out the California Current, we evaluated several sources evaluated a range of factors including the relative catches of landings and trend information for jumbo squid from of squid to hake, the frequency of occurrence of hauls commercial and recreational fisheries, resource surveys, with large volumes of squid, and the size composition and food habits studies. We evaluated catch records from of the squid catch during years for which no reliable Commercial Passenger Fishing Vessel (CPFV) records taxonomic identity of squid bycatch are available (V. north and south of Point Conception from 1980 through Tuttle, At-Sea Hake Observer Program NOAA/NMFS/ 2006.2 We also discussed the spatial and temporal dis- NWFSC, pers. comm.). tribution of squid with a large number of commercial To evaluate food habits, stomach samples were col- and recreational fishermen. Jumbo squid have also been lected from jig-caught jumbo squid in CPFV and com- noted in food habits studies of predators in the California mercial fisheries off of southern and central California, Current; Antonelis and Fiscus (1980) described them as as well as from jig, midwater, and bottom trawl gear common in the diets of northern fur seal (Callorhinus aboard the resource surveys described above. The loca- ursinus) off of California, and both Tricas (1979) and tions, dates, depths (including a range where appropri- Harvey (1989) noted their presence (albeit rare) in the ate), number of specimens collected, and size information diets of blue sharks (Prionace glauca) collected off of the for collected specimens are provided in Table 1 and Channel Islands and Monterey Bay respectively in the Figure 1. Although size (DML, in cm) was recorded for mid 1970s. Consequently, we considered the frequency all specimens, weight (kg) and sex were recorded only of occurrence of jumbo squid in the diets of California for a subset of specimens due to the opportunistic na- sea lions (Zalophus californianus) on San Clemente and ture of most collections. Weights were estimated with San Nicolas Islands, based from quarterly monitoring the standard weight (w) to length (l) relationship based from 1981 to the present (as described in Lowry and on 85 specimens ranging from 35 to 82 cm mantle Carretta 1999), as well as in the food habits of short- length, where: fin mako shark (Isurus oxyrinchus) collected from gill- w = al b (1) net fisheries off of southern California from 2002–05 Whole squid or stomachs alone were frozen at capture, 1Robison, B.