f
MARCH 1986
STOMACH CONTENT ANALYSIS OF SHORT-FINNED PILOT WHALES h (Globicephala macrorhynchus) AND NORTHERN ELEPHANT SEALS (Mirounga angustirostris) FROM THE SOUTHERN CALIFORNIA BIGHT
by
Elizabeth S. Hacker
ADMINISTRATIVE REPORT LJ-86-08C f
This Administrative Report is issued as an informal document to ensure prompt dissemination of preliminary results, interim reports and special studies. We recommend that it not be abstracted or cited. STOMACH CONTENT ANALYSIS OF SHORT-FINNED PILOT WHALES (GLOBICEPHALA MACRORHYNCHUS) AND NORTHERN ELEPHANT SEALS (MIROUNGA ANGUSTIROSTRIS) FROM THE SOUTHERN CALIFORNIA BIGHT
Elizabeth S. Hacker College of Oceanography Oregon State University Corvallis, Oregon 97331
March 1986
S H i I , LIBRARY >66
MAR 0 2 2007 ‘ National uooarac & Atmospheric Administration U.S. Dept, of Commerce
This report was prepared by Elizabeth S. Hacker under contract No. 84-ABA-02592 for the National Marine Fisheries Service, Southwest Fisheries Center, La Jolla, California. The statements, findings, conclusions and recommendations herein are those of the author and do not necessarily reflect the views of the National Marine Fisheries Service. Charles W. Oliver of the Southwest Fisheries Center served as Contract Officer's Technical Representative for this contract.
ADMINISTRATIVE REPORT LJ-86-08C CONTENTS
PAGE
INTRODUCTION...... 1
METHODS...... 2
Sample Collection...... 2
Sample Identification.... 2
Sample Analysis...... 3
RESULTS...... 3
Globicephala macrorhynchus 3
Mirounga angustirostris... 4
DISCUSSION...... 6
ACKNOWLEDGEMENTS...... 11
REFERENCES...... 12
i LIST OF TABLES TABLE PAGE 1 Collection data for Globicephala macrorhynchus examined from the Southern California Bight...... 19 2 Collection data for Mirounga angustirostris examined from the Southern California Bight...... 20 3 Stomach contents of Globicephala macrorhynchus examined from the Southern California Bight...... 21 4 Stomach contents of Mirounga angustirostris examined from the Southern California Bight...... 22/27 5 Previous accounts of the stomach contents Mirounga angustirostris, 1874-1984. [Citings listed are restricted to prey remains from stomachs only].... 28/31
ii LIST OF FIGURES
FIGURE PAGE 1 Length frequency distribution of upper hood length on Loligo opalescens from the stomach contents of Globicephala macrorhynchus and Mirounga angustirostris in the Southern California Bight...... 32 2 Age^ estimates from otoliths of Merluccius productus collected from the stomach contents of Mirounga angustirostris in the Southern California Bight...... 33 3 The upper and lower beak from an unidentified gonatid squid^(probably Berryteuthis magister or Gonatopsis borealis) found in the stomachs of Globicephala- macrorhynchus and Mirounga angustirostris from the Southern California Bight [Dorsal and ventral view of the beaks are on a scale of 5mm.]...... 34
iii INTRODUCTION
Stomach content analyses of four short-finned pilot whales ( Globicephala macrorhynchus) and twenty-one northern elephant seals ( Mirounga angustirostris) from the Southern California Bight are presented in this report.
The feeding habits and related movements of Globicephala macrorhynchus in the eastern North Pacific are essentially un described. Seagars and Henderson (1985) reported the remains of cephalopods Loligo opalescens, Moroteuthis robusta and Histioteuthis dofleini from the stomach of a pilot whale collect ed near Santa Catalina Island, California. Hall (1971) mentions squid "beaks" found in "several" of twenty-eight pilot whales stranded on San Clemente Island, California, and Kritzler (1952) reported squid "beaks" from the intestines of two pilot whales that died in captivity. Sergeant (1962) found that Globicephala melaena prey almost exclusively on the short-finned squid (Illex illecebrosus) in Newfoundland waters, taking fish (specifically cod, Gadus morhua L.) in the absence of squid. The range of the short-finned pilot whale in the eastern North Pacific extends from the tropics to the Gulf of Alaska, with greatest abundance south of Point Conception (Reilly, 1978; Fiscus, 1979). Walker (1975) describes a group of 20-30 animals considered resident to the Catalina Channel area inclusive of San Clemente and Santa Barbara Islands. Norris and Prescott (1961) suggested that inshore resident animals may be joined in winter months by an offshore group concomitant with the spawning season of the market squid, Loligo opalescens. The results from this study and the Seagars and Henderson 1985 report lend support to the suspected dietary reliance of the short-finned pilot whale on squid.
Analyses of stomach contents from northern elephant seals have been reviewed and augmented by several authors (Antonelis and Fiscus, 1980; Jones, 1981; Condit and LeBeouf, 1984), and are summarized and expanded in this report. The breeding range of Mirounga angustirostris extends from the islands off the Pacific, coast of Baja California, Mexico, north to the Farallon Islands, including a recently established mainland rookery off Ano Nuevo Point, California (LeBeouf and Panken, 1977). The non-breeding range continues from the Pacific coast of Baja California, Mexico as far north as the Gulf of Alaska. Sightings are reported seaward of the continental shelf (Kenyon and Scheffer, 1955; Delong, 1978; Antonelis and Fiscus, 1980), and in pelagic waters over seamount areas and submarine canyons (Morejohn et al., 1978). Return to and residence on the rookery sites, where seals "haul out" for up to two months for breeding and molting, varies according to age and sex (Antonelis and Fiscus, 1980). Little or 2
Tr.wr1^ted^n9 1 place durin9 this time (Scammon, 1874; nesend, 1912; Huey, 1924, 1925; Morejohn et al.,1978; Condit a^t^eBe0^f' ig84)- The return to sea after these periods repre- depa5tare /or Ceding areas north of the rookeries (Condit and LeBeouf, 1984), and the resumption of foraging behavior that is poorly understood. g
METHODS Sample Collection
Stomach contents from four pilot whales and twenty-one elephant seals were available for examination. Samples were Wlthin the Southern California Bight from 33°42'N to 34 26 N over a period of fourteen years (Table I and II). All of the elephant seals and one pilot whale (WAW-790) in the sample wawe/inctrandjd °f unknown cause. Pilot whale samples WAW-404, WAW-405, and SBMNH 77-54 stranded as a result of incidental v^SVffoeS mortalltY- Elephant seal samples 72-77S, 73-141S, and 73-133S were stranded alive and maintained in captivity for hree, four and six days prior to their death. The animals refused food during this time. Stomach contents from these three animals were retained from meals prior to the date of collection and captivity.
Stomach volumes were obtained on three of the pilot whales and one elephant seal. Excess liquid was drained from the stomach contents and the amount of water then displaced by the material was measured by graduated cylinder. In all cases stomachs were rinsed and the contents were rough sorted by a flotation-decanting technique (as described in Jones, 1981) and stored in. alcohol. Sample Identification
Cephalopod beaks, otoliths (sagittae), elasmobranch egg cases and fleshy remains from fish and cephalopods were used to identify prey species. Cephalopod beaks were identified by comparison with the reference collections of the Santa Barbara Museum of Natural History, Santa Barbara, California, of the r\lker iPr^Vate c°llecti°n/ Los Angeles, California, and IT+tof the National Marine Mammal Laboratory, Seattle, Washing- descriptive references included Iverson and Pinkas (1971) and Voss (1969). Otolith identification was made by the late John E Fitch, California Department of Fish and Game. The otolith reference collection of the National Marine Mammal Labor atory, was also used for comparative purposes. Elasmobranch egg cases were identified to species based on Cox (1963). Voucher specimens for otoliths and cephalopod beaks are archived at Santa Barbara Museum of Natural History. 3
The highest number of either upper or lower cephalopod beaks was recorded as the maximum count for each species present (Table 3 and 4 ). Because deterioration of the otoliths obscured any distinction between left and right, otoliths from each representative species were totaled and halved, resulting in a minimum estimate of the number of fish present. This should be taken into account in Figure 4. Egg cases were recorded indivi dually and included in the total count of fishes. Sample Analysis
' The number, frequency of occurrence and length estimates of ingested prey were recorded (Tables 3 & 4 ; Figure 1). Avail able volumetric data is presented in the results section. Beaks and otoliths were used to determine body lengths of two of the dominant prey species (the market squid, Loligo opalescens, and pacific hake, Nerluccius productus).
Upper hood length was measured to the nearest .01mm. on 676 Loligo opalescens beaks. Beak length frequency histograms are presented in Figure 1. Kashiwada et al., (1979) determined that upper hood length (UHL) correlated most highly with mantle length among a series of beak measurements on Loligo opalescens from southern California. An approximation of mantle length using the findings of Kashiwada et al. (1979) from a combined sample of males and females is discussed. Loligo opalescens beaks from this sample were in good condition, showing little or no wear. Hake ages were estimated from a known age-length series of 31 otoliths from hake collected off the California coast in 1979. The approximate ages and body lengths were then compared with findings from Dark (1975) for hake collected off California, Oregon and Washington, 1965-1969. The age categories assigned to the hake otoliths are illustrated in Figure 2. Due to erosion of otoliths in the stomachs, the size of hake were underestimated by this method.
RESULTS Globicephala macrorhynchus The 647 prey items recovered from the pilot whales consisted entirely of cephalopod beaks and fleshy remains (Table 3 ). Loligo opalescens was present in each of the four stomachs com prising 617 (95%) of the individual food items present. The onychoteuthid, Moroteuthis robustus, occurred in three stomachs totaling seven individuals. A total of nine Histioteuthis dofleini were present in two stomachs. In the only other report of identified remains from the stomach contents of the 4
short-finned pilot whale, Seagars and Henderson (1985) counted an approximate one hundred fourteen L. opalescens, one M. robustus, and one H. dofleini from an animal collected near Santa Catalina Island, California.
Two lower beaks of an unidentified gonatid (probably —^^^yteuthis magister or Gonatopsis borealis) were present in one stomach. The beaks were compared to the Clarke and Macleod (1980) voucher specimen for Berryteuthis magister (identified from the stomachs of sperm whales taken in western Canadian waters) and found to be very similar in structure. Berryteuthis magister is subarctic in distribution with Oregon as the known southern range extreme (Young, 1972). Gonatopsis borealis, also a subarctic inhabitant, is common to southern California waters (Young, 1972). To date, the two are considered indistinguishable by comparison of beak structure alone (C.H. Fiscus, pers. comm.). The beak specimen from this sample is illustrated in Figure 3.
. The length—frequency distribution for upper hood length of L°llg° opalescens beaks ranged from 4.4 to 11.5 mm. (Figure 2). The corresponding approximation of mantle lengths from Kashiwada et al. (1979) range from 90 to over 200 mm. Specimen SBMNH 77-54 contained fleshy remains of L. opalescens including intact mant les with egg masses, gladii and beaks. Mantle length measure ments on fifteen of these specimens ranged from 110-170 mm. with a mean of 138 mm. Seagars and Henderson (1985) estimated a range 112-142 mm. with a mean of 128 mm. for mantle length measure ments on eleven intact or nearly intact L. opalescens from their sample. The average diameter for individual eggs present in gravid specimens from sample SBMNH 77-54 was 2.0 mm.
Stomach content volumes were recorded on three of the four samples: WAW 405 = 1.2 liters; WAW 790 = 0.6 liters; SBMNH 77-54 = 2.2 liters.
Mirounga angustirostris
Fishes, including egg cases and egg case remains, were the dominant prey in the 21 elephant seal stomachs examined. Cephalopods were second in abundance and percent occurrence (Table 4 )•
Fishes occurred in 100% of the stomachs representing 54% of the 307 prey items recovered. The most highly represented fishes m both number and percent occurrence, were the cusk eel (Chilara taylori), Pacific hake (Merluccius productus), ratfish “ ( Hydrolagus colliei), and plainfin midshipman ( Porichthys notatus). Nineteen percent of the fish were represented by egg cases from pacific hagfish (Eotatretus stoutii) / ratfish, and the 5
Rajidae. Egg cases were present in the same stomach with the fleshy remains of ' adults' of the same species in only one instance (E. stoutii, Table 4 ). Egg cases and egg case frag ments recovered from the stomach contents were hardened and dark in color.
Seventy-three percent of the 63 hake otoliths examined from this sample were from fish of age groups one through three based on otoliths from the known age-length stratified sample of hake (Fig. 2). Forty-four percent of these were between two and three years old and approximately 25-31 cm. in length. This projected length range correlates well with the average body lengths of 26.93 cm. and 28.03 cm. found by Dark (1975) for male and female hake within this age range, although some variation in age and length between different year classes and geographic locale should be expected (Dark, 1975).
Eleven species of cephalopods were present in 17 of the 21 elephant seal stomachs examined (Table 4 ). Loligo opalescens was the most frequently represented prey. It was identified from 13 (62%) stomachs representing 29% of the total prey and 67% of the cephalopod sample. Octopus bimaculoides was identified from 33% of the stomachs examined. Two lower beaks from the unidenti fied gonatid (probably Berryteuthis maqister or Gonatopsis borealis) similar to those m the pilot whale sample were found in two stomachs (Figure 3).
The range in UHL for opalescens beaks from the elephant seal sample was 3.2-10.2 mm. with associated mantle lengths (Kashiwada et al., 1979) of 80-160 mm., and 80-200 mm. for males and females respectively (Figure 1).
The crustacean, Hemisquilla californiensis, family Squillidae, was found in five stomachs-! Remains of Tunicates and the red crab (Pleuronocodes planipes) were not included in the prey totals due to the difficulty of obtaining an accurate count, however, volumes are given in Table 4 .
Prey species previously unidentified in M. angustirostris stomach contents (Table 4 & 5) included the following fishes: the angel shark (Squatina californica), body parts and egg cases of the horn shark (Heterodontus francisci), whole specimens and body parts of the thornback ( Platyrhinoides triseriata), egg cases of the big skate, Raj a bmoculata (egg cases of Raj a sp. were identified by Huey in 1930), the northern anchovy (Engraulis mordax), the black eelpout (Lycodes diapterus), the sablefish ( Anoplopoma fimbria) and the pileperch ( Damalichthys vacca). Newly described cephalopods included the gonatid Berryteuthis magister or Gonatopsis borealis (probably identified m prior 6
bistmfudcuielos idSesG°__n_aa_nri_ _P_viS i>or;alis>- gg?th°® tuberculata. Octopus 3;des' and yampyroteuthis infernal!^Pfi^usi~ v nn-)US described crustaceans and tunicaTi^ Previously un- £aliforniensis. Pleuronoco5eS~ niVn~ p~^ Sgmisquilla Thetys vagina. )soma atlanticum, and
DISCUSSION The feeding habits of a predator can be determined from s omach contents only if the sample is representative of the ^ural Population and of statistically adequate size Since an efficient predator's selectivity of prey is likely to shift with the varying availability of that prey (Emlen, 1966^ Morse 1980) sample collection should range over an extended period of time ' ent to the* collecting conditions- The restrictions inher it oafrltnhees“te^aPlLS shi^em;yabeginetoneme?ge.1S aCOUmUlated' Predator-prey relation-
gir°un9a angustirostris sample was composed entirely of bias tht' nanturiS1„Zf tbUVeIllei
?fults from this study suggest that egg cases and whole animals represent two different prey and that egg cases mav be directly targeted as a food source by the elephant seals Little branchCfiesh5aLmain,madedbetUeen th® identifi®ation of'elasmo- ranch fleshy remains and egg cases in previous studies (Table ). It seems to have been generally assumed that egg cases «avld femaS o?°?b»fS 316 introduced "ith the consumption of a gravid female of that species. Egg cases of oviparous species are pliable upon extrusion, hardening with exposure to the en vironment (Dean, 1906; Wourms, 1977). Egg cases introduced coin cidentally with a gravid female would be expected to diaest fron^each hardefled and darkened egg cases were identified from each of the oviparous species encountered in this study spLieseinWonlv one i^tether With fleShy remains from the same SsS ly ? instance. Sample WAW-795 contained four egg and two nearly intact specimens of Eptatretus stoutii. No 7
egg cases were found from the stomach containing the ovovivi- parous Platyrhinoides triseriata. Egg cases are typically laid in rocky crevices around plant growth in shallower (20 m. ) inshore waters, but occur in deeper water as well (Dean, 1906; Feder, et al. , 1974). Hydrolagus colliei spawns year-round with peaks in the late summer and early fall. Both egg cases and adults are found in as little as five meters of water in Puget Sound, but are more common from 37-140 meters in the Monterey area (Dean, 1906). CephaloscyIlium ventriosum, is common to kelp bed areas in depths of 5-47 meters from the Gulf of California to Monterey Bay. Individuals are nocturnal, dwelling in crevices during the day. Egg cases are found in the same areas as adults (Feder, et al., 1974). At least six of the prey species identified from the ele phant seal stomachs may be attributed to the influences of warm water insurgence or secondary introduction. Sample SBMNH 83-34 appears to have been influenced by both factors. Stomach con tents yielded a volumetric measurement of .31 liters, .23 liters of which were attributable to Pleuronocodes planipes, a pelagic warm water crustacean. Pyrosoma atlanticum, Thetys vagina, and a small beak (3.3 mm. UHL) from Ocythoe tuberculata were also found in the stomach of this individual. Ocythoe tuberculata males are small (up to 20 mm. mantle length) and known to occur m the body cavity of Thetys vagina, an epipelagic salp (Hardwick, 1970). Thetys vagina is generally restricted to warm temperate waters, but, can be carried to northerly latitudes under certain condi tions (Yount, 1958). Sample SBMNH 83-34 was collected in 1983 - a year heavily influenced by El Nino. Secondary intro duction may be a causal factor in the presence of some smaller less highly represented organisms in the sample. Sanddabs (Citharichthys spp.) and northern anchovy (Engraulis mordax) for example, are both known prey of Pacific hake (Best, 1963). Hake occurred in each of the samples associated with these two groups (Table 4 )• Varying rates of digestion, secondary introduction (Perrin, et al., 1973; Walker, 1981; Mead, et al., 1982), and the presence of a large number of small organisms relative to larger, poten tially more calorically valuable prey, are the primary sources of bias in obtaining volume, number and frequency of occurrence values in marine mammal stomach content analysis. In addition, the presence of prey hard parts, such as otoliths and cephalopod beaks, may represent an accumulation of meals spanning over a period of days or even weeks. Examples of retention have been cited by Kritzler (1952), and Condit & LeBeouf (1984), and were noted in this study as well. Biomass estimates may be influenced by seasonal and geographic factors. Length projections, on the other hand, provide a less variable measure of bulk than weight. 8
In addition, many species of fishes and cephalopods are strati- ±:L^dr,in thfn water column according to age or size classes (Fitch and Brownell, 1968; Dark, 1975; Roper and Young, 1975) in which case, length estimates may also provide insight into predator depth ,and seas°nal shifts in food preference. Berg (i Larid Hysl.op U980) have made thorough and critical reveiws of methods typically, used in quantitative analyses of stomach contents. The validity and reliability of the various methods discussed are examined m reference to fish feeding habits, but are applicable to marine mammals as well. Traditional methods lor quantitative assessment of prey items include volume, number and frequency of occurrence, and biomass or weight estimates. None of the methods provides a satisfactory measure of prey preference and selection when viewed independently. As a result numerous researchers have applied single formulas that mathemati cally combine the independent measures of volume, number and frequency of occurrence. Pinkas et al. (1971) developed an Jn(^ex of Relative Importance" (IRI) in an attempt to describe the relationship between prey items in a sample. The IRI repre- sents the sum of number and volumetric percentage values multi plied by the frequency of occurrence percentage values. Other researchers have since utilized the IRI or a modified version of it (Bureau, 1969; Karpov and Cailliet, 1978). Each of these attempts are of value in presenting a composite picture of prey selection by a given predator if the individual components are listed separately as well for cross-comparison between studies. owever, the bias introduced by each of the independent variables into any mathematical equation of this type could potentially compound the error in the final numerical measure derived.
Prey availability and selection, and related movements by both predators under examination in this study are likely influ- enced by the unique physical characteristics of the study area itself. Point Conception marks the northernmost boundary of the outhern California Bight. The California Current arcs south to southeast and north again along the California coastline as the Southern California eddy where prevailing north-northwest winds miluence seasonal periods of upwelling (Reid, et al. 1958- Emery, 1960; Ebeling, et al., 1972; Littler, 1980). The strong est periods of upwelling begin off Baja California in April and May, and become most marked off southern and central California m June. This seasonal pattern is coincident with the northward and inshore movement of prey important to elephant sea s and pilot whales, particularly Loliqo opalescens and Merluccius productus. ------
Loliao opalescens is primarily neritic and especially preve- the waters of the California Current. Schools are segre gated by size during the spawning season and probably throughout 9
their pelagic non-breeding existence as well. Spawning takes place in southern California December through March and July at depths of 25-35 meters. Spawning activity in Monterey Bay ex tends from April through December with major peaks in May and June at 20-55 meter depths. Population movements between spawning seasons are unknown (Fields, 1965; Hochberg and Fields, 1980; Roper, et al., 1984).
Merluccius productus displays both latitudinal and diel vertical migration. Within its range, the pacific hake shows greatest abundance in the coastal region of the California Current system. In late spring, summer and early fall, adult feeding schools are most abundant in the inshore northerly waters of Oregon and Washington in depths less than 100 meters. Local concentrations of hake are also present off northern and central California in spring and fall. Individuals migrate diurnally during periods of feeding activity and can be found dispersed from the surface to 20 meters at night. They descend to form schools during the day. Spawning takes place offshore November through March at intermediate (275-299 fathoms) levels in the water column. No diel migration or feeding takes place during this time (Best, 1963; Gotshall, 1969; Grinds and Tillman, 1970; Nelson and Larkins, 1970; Bailey, et al., 1982).
Diel vertical migrators are known to disperse in their ascent in the water column (Fitch and Brownell, 1968). If this is the case for schooling prey such as hake and loligo, then deep diving by elephant seals during daylight hours may allow access to a more concentrated food source. In this sense, deep diving could also eliminate potential competition from other predators comparatively less adapted for deep dives. However, the direct targeting of diel migrators and schooling species during their seasonal nearshore activity would eliminate the energetic costs of deep diving. In addition, nocturnally active prey that tend to burrow in the daytime are not only more available but, in some cases, more highly concentrated at night (W.A. Walker, pers. comm.).
Standard sampling techniques and fisheries observations do not fully characterize the locality of lower trophic level organ isms (Jones, 1981). It may be that prey are being taken by elephant seals in offshore areas north of the rookeries as sight ing and tagging data suggest (Condit and LeBeouf, 1984). Ele phant seals are adapted for deep diving (Eisner, et al. , 1964; Simpson, et al., 1970) and have been recorded at depths of 183 meters (Scheffer, 1964). However, the primary prey species consistently represented in elephant seal stomachs are present in shallow coastal waters, at least on a seasonal or diurnal basis. Many are nocturnally active, burrowing in the substrate or hiding 10
in crevices by day. Onychoteuthis borealiiaconicus i^ mnct zoS °darrrd n^hf ep^pglagic and nearsCe 1004^' dn^ night (Young, 1972; Anderson, 1978; Roper et al. , interti gftOPUS ^aculoides typically inhabits the mid to low intertidal zone or sub-tidal to 20 meters depth in protected +-r°Sky-areaS/ and kelp beds (Hochberg an(j Fields, 1980). n pth records indicate the upper daytime limit for ifo ande?oo1Sm T^letr°w ln Monterey and southern California to be 20 nmeters* However, individuals are spread throughout the water column at night and are highly represented in the^pper Jh lamratertSav YOUn9'- 1972; RoPer and Young, 1975; Anderson, 197*?). g-hlIaP taylori, is nocturnally active, it is commonly found rr ?urrowtd tai1 first in sand and muddy substrateUin depths of less than 18 meters, but has been found as deep as 244 i er^ (Miller and Lea, 1972; Fitch and Lavenberg, 1975). The plainfm midshipman, Porichthys notatus, burrows or -in sand mud or rocky areFF nearshorrtF30S meters, spawning in the lntertidai zone in late spring and summer (Miller and Lea9 1972- Feder, et al. , 1974; Fitch and Lavenberg, 1975; Gotshall, 1981)'.
Elephant seals may be searching for prey in both deep and condign, dePendin9 perhaps upon sVanS age, contents of Season' Tbe Pri™ary prey represented in stomach “tS Mirounga angustirostns suggest that it is an oppor- itv a^d beedln? habits likely related to seasonal availabil- ty and abundance of prey. Elephant seals are capable of divinq at depth dandhin th^7 selectin9 P^ey that are available both depth and m the shallows on a diurnal or seasonal basis.
compaJativpP aldatadat-SamPle Prevent S±? edefinitiveU limited c°Hectionconclusions period regarding and limited prey occurrenrpSnfm0ng>,gT-0blfphala macrorhynchus. However, the 100% ^rence of cephalopods, and predominance of Loligo opalescens “ „th? hhoP 1S, fr°ngly sug9e=ts selection for thl^-pafticular prey m the study area - at least during the fall and winter when the samples were obtained. wnen 11
ACKNOWLEDGEMENTS
Special thanks to William Walker, Natural History Museum of Los Angeles County, who provided the bulk of the specimen material and critical review for this report. Robert Jones, Museum of Vertebrate Zoology at Berkeley, and Charles Woodhouse, Santa Barbara Museum of Natural History, generously donated additional specimen material. Instruction and assistance in cephalopod beak identification was given by F.G. Hochberg, SBMNH, and Clifford Fiscus, Seattle. Fish otolith identification was made by the late John Fitch, California Department of Fish and Game.
Further comment on the text was provided by George Antonelis, Howard Braham, and Thomas Loughlin of the National Marine Mammal Lab oratory in Seattle; William Pearcy of Oregon State University; and Lisa Ankenbrandt, Camille Goebel—Diaz and John Sinclair of the University of Washington.
I wish to thank Laurie Marx, SBMNH, for her meticulous illustra tion of the gonatid beaks. Betty Goetz of the National Marine Fisher ies Service in Seattle determined the approximate age categories for the hake otoliths, and Melodie Tune, Seattle, illustrated the bar graphs on Loligo and hake. 12
REFERENCES
Ahlstrom, E.H. 1965. Kinds and Abundance of Fishes in the Current Region Based on Egg and Larval Surveys CalCOFI, rep. 10, p.31-52.
Anderson, M.E. 1978. Notes on the Cephalopods of Monterey Bay California, with New Records for the Area. The Velioer 21(2) .-255-262. y
Anthony, A.W. 1924. Notes on the Present Status of the Northern Elephant Seal, Mirounga angustirostris. J. Mamm. 5:145-152. Anthony, A.W. 1925. Expedition to Guadalupe Island, Mexico, in 1922:The Birds and Mammals. Proc. Cal. Acad Sci 4th Series, 4(13):277-320.
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TABLE 1. Collection data for Globicephala macrorhynchus examined from the Southern California Bight.
SAMPLE SEX LENGTH (cm) DATE POSITION
SBMNH 77-54 unk. approx. 440 11/23/77 34°06'N, 119°53' W
WAW - 404 F 461 10/14/75 33°44'N, 118°22'W
WAW - 405 M 660 11/07/75 33°44'N, 118°24' W
WAW - 790 M 540 12/10/69 33°50'N, 118°24'W
Santa Barbara Museum Natural History, Santa Barbara, CA. W.A. Walker private collection, L.A. County, CA. 20
TABLE 2. Collection data for Mirounga angustirostris examined from the Southern California Bight.
SAMPLE SEX LENGTH (cm.) DATE POSITION
1 WAW-795 F 161 3/12/69 33°45'N, 118°23'W
WAW-M/1 F 143 2/14/70 34°01'N, 118°30'W 1 72-77S M 152 1/31/72 34°01'N, 118°30'W
WAW 796 M 163 2/20/72 34°01'N, 118°49'W
WAW 797 M 159 1/10/72 33°45’N, 118°23’W
72-86S M 140 4/24/72 33°44'N, 118°22'W
WAW-798 F 156 1/20/72 34°02'N, 118°40'W
73-124S M 166 1/18/73 33°44'N, 118°22'W
73-133S F 163 2/14/73 33°56'N, 118°27' W
73-135S M 150 2/21/73 33°44'N, 118°22'W
73-141S F 143 3/22/73 33°53’N, 118°25' W
WAW-799 M 123 3/12/73 33°42’N, 118° 17 ' W
WAW-800 M 173 4/01/73 33°43'N, 118°11'W
WAW-801 F 231 4/08/73 33°50'N, 118°24'W
WAW-802 F 196 5/10/73 33°43'N, 118°19'W
WAW 803 M 157 7/21/73 34°02'N, 118°45' W
73-202S M 201 12/16/73 .. 34°02' N, 118°35'W 2 SBMNH 77-52 M 186 11/15/77 34°25'N, 119°53' W
SBMNH 79-18 M 380 '4/17/79 34°25’N, 119°46'W
SBMNH 81-12 F 187 4/13/81 34°25'N, 119°40'W
SBMNH 83-34 M 134 5/03/83 34°26'N, 119°57' W
W.A. Walker private collection, L.A. County, CA. Santa Barbara Museum Natural History, Santa Barbara, CA. 21
o o O cr\ n-
in in o in m w o Southern U1 CJ o o o 0-2 O o o o m in in m o m w in cm cm CM CM x m n» XPi CJ from the from CJ o o a O o m CM vO cn VO r-4 $-2 O o m • • • Pi o> O O w —• o o o ^ CQ • r- n- o Globicephala 00 c/3 3 •H U of •H 10 O •H c a o 3 •H o w O qj u a u X f—1 QJ a ft >* GJ 03 ft 4-1 o s rH X C/3 '•—) o qj 3 4-1 X CO •H i—4 C/3 X X 4-> 03 • H r-H 03 3 •H 4-> ft •H 3 cn •H X • r4 Stomach c/3 QJ ft X 3 3 X 3 C/3 cm QJ ft X 3 X HD 03 o X QJ QJ Ml qj *H X o X QJ X HD 4-> qj >J o 3 4-> 3 Ml C/3 X X 3 X 3 ft •H o QJ o o QJ o 03 3 O M 03 QJ O QJ 3. o a 00 X • r—i •H 4-1 04 T3 Ml QJ M C X X X t—4 •H *M o 4—1 4-1 o o •H 03 HD QJ o O u O 03 H 00 r—1 •H c/3 00 ft Ml Ml 3 •H X CJ X >. V4 X 03 •H o X • r-i •H o CJ 03 O 3 u G o a* x r—i ft C/3 X X 4-1 o a CJ 3 >> o r: o qj o o •H u o G TABLE ft H CJ H ft X . o o o 22 CT\ CO r^* r- CO r- md 3: i • oo 5; CM CM • x: r^ CM CO CO to to r-. CO w ov o> CO oo co ►-3 CTN o O tO tO o o co uo OV O r-H C CM S o u th ern th e o S'S o ON r- co from to CO o o to ^ o o vO CM CM t—» cn -X u angustirostris 03 XI JC 00 CO •H -X Jh X-4 XJ Vh 03 00 co 03 jd 03 co •H a; x: CO co CO Jd d 4-1 CO •H d CO d 00 d 'r-i M irounga 03 o •H x 03 03 E TP 0/ o gj E E oo -d o f x GJ GJ >> a X Li o d 03 03 >> •H CX >> >* x: cx u JG 00 CO X GJ co CO CO •H GJ QJ U CO d 03 c o n te n ts 03 •H V-4 -C 4-< CO 00 4-> GJ C GJ CO CO GJ • H CO CO c 03 CO d GJ 03 r—i d GJ GJ co 03 TP 3 CO E 03 GJ CO TP r—i GJ CO u GJ •H 4-) E 03 • r-4 >> E 03 a CO •H (J 03 3 03 GJ 4-> •*-> d CO • r-< U c o CO • r-i U 3 QJ O TP 03 d o Stomach 03 GJ 3 U •H CO 3 u o 03 00 V-4 d O TP TP in X CX 00 O GJ 00 -d OO GJ oo TP 3 03 a -h . TJ O Lt oo Li r-H X •H 4-) 03 CO GJ •H i-H CX CX oo cx •H 4-> o u 03 CO GJ 03 03 4 Cl, W W O CO d 03 i-H 03 4~> • ** . ~ CO O' CO CO CO CO CO cn CO o O o* CO O' CO 00 oo O' r—* i r—i 1 1 1 1 5 1 3 04 04 04 CO < CO < O- O' lO O' 3 O' 3 O' . ~ .« . ~ .~ r—i CO CO CO O' o m o oo U3 o '—* o o CO X CO Bight, 4.8 California 1 Southern the 0.3 from 1 angustirostris u 03 X C Mi /•—\ /'-'N o C/3 C/3 CO CO x a c c C X •H •pM •H •H 03 CO -<0 X CO Mirounga g d) e G CO G CO dJ x % CO >. >. CO >% Ml X X X Mi X PM oo V X M. CM oo CO Ml PM oo Ml r—i Mi 00 2) CM co u >. •»M CO dJ 03 CO CO dj CO CO dj d3 o CO CO dJ >% X > v_/ T3 CO CM / <0 v—y CO Mi - CM CM >• x X CO o •pM •H T3 •H 4. •n G CO <0 r—1 > CO > <0 > •H >> > (X •H p-M Pm o CO PC O PC o X o cm, PC Pm CM o unidentified (cont. TABLE 24 On CM • ** CO CTN cn on r^- O CO uo ON r-* i CO CO i 3: — I i 3: i l CM C i 3 uo < < CM O0 3: r: Zi < I r-~ r^ vO CO ON —* m ^ co co CM VO OO vO ON ON O vj O ON o o- 4-> jg 00 •H CQ C G O QJ oo CJ oo CO oo CO oo S; •M- oo G o 00 G o oo cm H 5-5 oo vO oo oo 4h o m o CM CM o o m c r^- oo oo in g C C£ 03 C E 03 CQ 03 > jg CJ 00 > in -X c O 73 03 CJ 4J -G •H JG u CJ G o E I u c U O •H «3 G •H a JG jG •H CO r—H cn x: *4H 3 u G 4h CJ •H o u <4- Q C U CJ Mi CJ CJ C •H 03 73 CJ CQ -G J*S r—H 03 CQ QJ CJ in aJ r—H u X rH ■i—l Vh O. 03 JG 03 •H c O rH cn cn cn o CQ CJ G G JG •H 4J CO cq 4-> CO c G CJ •* -X 03 03 o X 4-) G cn u •H u u 03 03 73 G 0 u u T3 4-) O Q H JG 03 -G '* ' Q u • O 03 G 4J 03 -H 4-) CQ 1—* 03 CJ E "O CJ CQ • 73 Oh cn c 03 •H CO >> 03 CJ CQ •H 6 03 CO 03 CJ >> o o 73 CO "D >, •H 03 in 4J (TJ 73 3 CJ 4-> 03 JG *-> u •H -H •H _c 73 'V 03 E •H *fH 03 T3 4J 00 v—' 73 rH O 4-1 •H U CJ •h in E O •H JG •H 3 TJ 03 03 cn oo jg sz U U •rH H G CJ 0 a U U • C/3 rH (T3 73 CJ CJ 4J u 0 O 3 • H CQ 0 O -H 1 OJ G H 03 -H 03 •H 73 03 cn G r-H 7G rH O rH 4J rH >• JG 03 OO O O rH a U U rH 1-J •H •rH CQ 03 O 03 M CO »-i c 4-> O G a; Q O U JD CQ O •h E •H jg JG 03 >, UJ *-» 60 tu 03 Q~* cj x O CJ 0 c JG 03 c ^ Uj w CQ CQ O O Ml U CO G < 1-4 x O E CQ CQ o CM CO < W < u E-« 25 UO •—• CO av 1 CN X CM O i • ~ • — r—« CM 3 ON '-• •» co 00 1 < ON o CO CO CM ,—« CO r- co r^. CO o oo r-- i 1 r—1 CM . «N 3 3 l 1 1 . . ~ -3- CNJ < < CNJ co CO CN CM CM CM CM CN CO uO 3: r^» |Ns uO tO U0 *—• uO i—• I co r- r- O- r—< r^- r—i X oo co o co CO 00 r- r- oo oo w av CN o O W 00 00 00 oo California uo to CJ ^ r—« CN Z 00 VO CO co o co VO VO O O uO o e a co cn vO tO 00 CNJ angustirostris Mirounga c/3 of • H x •H w C3 c X u /—S x •H o X T3 o OJ X OJ a rH . CJ •o •H • r-i ■H •fH X XJ TJ X "U •fH X X •H • U3 Stomach X X x> CJ Q. X 3 3 aJ 3 1/3 tM o X U o TD O 3 QJ OJ 3 4. 03 x o c o M O o aJ o T3 3 c c X TO 03 r—i 0C c ■r-i o • H • H o X ■ r-i X CM rv, fv- . - co CO co . •, o CO CM o CO 00 CO o 00 vi x 1 co CN i CM r—i 1 3 T—> 03 CM vi- < 1 CO < 1 vi CO U0 CO rv. CO CO co 1 1 1— . - rv. i rv CO . «s . ~ • ~ CO CO CO rv oo U0 . ~ co CO w CM U0 • •* co oo CM ON CO 1—1 o CT\ ►—3 O pr; CO uo o X N rv vi CO |v rv co pr* a, CM CM rv r—H 1 I 1 fv. r—• 1 1 2 3: i 1 3: 3 i 1 § < co CO CQ CQ < CM co < < CM co CQ co rv fv* CO CO rs rv 3: 3 rv rv CO Bight. uO CO CO co CO oo CO vi- ON vi- co Southern CJ the E 3 co CO co r—A VO co CO o > from o o o o C CO CM cx C/3 angustirostris C/3 •H X X 3 C/3 dJ 3 X U o Mirounga •H X G •H O X of cx CJ 03 >> 03 CO •H pH G contents X (X cx '—/ H >* cx X (—< *H 03 3 O X CX 6 C/3 •H S pH a/ cx o >> G •H X c >% u 4-> U X cr x O PU X o o o > .u CQ CJ CO < H 27 c 03 3-4 d) Bight, 36 C r—1 00 CO 00 CO ^ vf California Southern the from angustirostris Hirounga of c 4-) 3 G E u 03 u •H r—4 o 4~> 4-) <+-« contents G 03 03 d) • 03 4—> T3 03 U •H dJ 4—> 03 03 03 6 E J 03 w o o •H 4-> - o u u O* u J* f-< JC >>04] £ co H 04 CO (cont. TABLE 28 00 r- ON oo ON CO o QJ CO g & qj > g QJ L4 >» 03 XJ C QJ -C u CO w e U 03 •H 3 Cl -C L-l rH e Xj CO 00 o 03 co 0) 03 U •H 4-J XI :* <4H 03 f-H CO oo U U 03 o •H X X G -G L-i X •H £ co •H QJ u >, O U 4~> 03 c X Ll x: CL, •H X> CO 4-) p-i QJ CL u >> 03 > co G 03 L» 03 CO 03 Li X «. 4-J 3 X5 03 QJ X *r4 4-> G O G QJ c E C 03 • H G co QJ 3 E rH QJ X X 03 3 CO rH 03 -H G i—< r—4 QJ o QJ X> CO X V4 03 03 QJ o 4J u CO •H U| U QJ u 03 X co QJ >> CO 3 4J 03 •H 3 X CO u CO o 03 G 03 G U QJ QJ 10 03 CO CL U •H 03 O J-4 QJ CO 3 O 03 L< 00 N 4J o CO L-» V-l •k X3 03 in 03 3 -G rH X 4-) oo >n QJ oo •H X) CO X r-4 V-l oo *H r—4 co •H 03 OJ 03 QJ - oo 4-J QJ M O 6 C^ •H 03 O oo a qj g u -C 03 03 QJ G 4-J u QJ L» >• O E H 3 G N •H ^ <] CJ •x C£ >» QJ cr u •H > CO CL, t*4 03 G n 0-i co CO -G 3 CJ 29 CO on C/3 QJ a o . 0 . - CO o x 0 r- OO r- 00 0- 1—4 1980 ON ON ON . ON ON OO rH CO OO r-H rH CO OO CO r—< r—* 1970 1— r- r- n- C/3 on - ON ON - *• ON ON ON - - G 1978 r—i N rH rH MH N r—i f—• t—i CM N U 1978 4-> 0 4-J G 4-> (A r. rH - 0 rH *» •* O r—i •H , • •• «3 • • QJ 03 QJ 03 pH Fiscus, r—i CQ PQ rH 03 03 03 QJ 03 03 03 QJ XJ al., al. m ON XI 04 G X ►G X X? r—i 4-> C 4-J 4-J G 4-J 4-) G ON C 03 and 1—4 and et C/3 W G G CJ a X C G G 03 C G G C 03 c •H si G si si si si jg si si si r—4 o QJ o o 0 4-) 0 0 0 0 4-> G 0 QJ o > CO ) • 1 ) •r-) -H •x •x •x • H O •x G 1874-1984. CO qj c QJ QJ QJ X) QJ QJ QJ QJ X JG QJ O only]. Vh VH V-i Vh in 4-J u 3 V4 G i-< G 4-J U , o o O O 0 0 0 O JD O O c jD G Morejohn Morejohn sc H r; 2: r: 0 x: x: XI x: QJ < X! < Antonelis Morejohn stomachs from angustirostris sole) sole) remains rex Hirounga , si sole prey C/3 , ) slender to -X r—“\ , c u CO rG 03 0 G 03 zachirus contents V4 G X is e g •H X 1 •* G G jg • CO 03 CO QJ •H CO exi G X rH CO u Lyopsetta CJ GO QJ •H 03 QJ G G G E JG QJ CO 03 •H restricted stomach sole •H •H O QJ gJ U-i or X3 G U -X •H 4-J •H u u Jh •H •H CO O CO Vh U QJ 03 <4H <4H G O 03 O 03 the are si CO G •H u 03 JG G rex •H U u QJ •H , u U 03 03 X 0 CQ QJ r Glyptocephalus Lyopsetta of •H •H rH G QJ PQ X CO '4-4 'H G 4-J JG >> O G • H •H *. 4-J CO rH O X U CJ CO O CO •H Q CO •H listed 03 03 CO G G G Hh •H X 04 04 G 4-> CO G -X CO >4 V-4 4-J U •H U CO rH 0 — 03 G r- G O 0 rG CO zachirus •r4 X 4-J X •H CO V4 G 03 Glyptocephalus accounts (possibly ( •H 03 O O VH •H Hz' JG CO (possibly C/3 CO G QJ u O O O /—\ 03 03 QJ G r—i G X in >. - • r—H (O 03 CO 03 JG [Citings >. G QJ G 4-J rH X QJ QJ CO 03 QJ Gj CO •H 4-J G 03 CO •H >, 03 G 4-J 03 Hh JG O oJ G X JG X *H QJ X CO CO •H CO U U QJ O •H 4-J •H (J 03 03 •H QJ QJ 4-J QJ •H 03 03 G O JG •H U X U G 4-J 4-J G 4-J QJ V-4 Previous XJ QJ •H JG U O G *H 03 QJ CO CO QJ CO 03 03 2) CA •H CX X) U -H O r—i * H r—i 03 03 03 X 03 x si . QJ QJ G V-4 03 VH G Vh X -H G JG Si •H Si •H 4-J - si G rH 03 u 0 rH QJ •H JG V-4 QJ QJ QJ JG *H 5 G C/3 4-J 04 Pleuronectid unidentified G CJ CQ V4 X JG CJ O CQ CQ G CQ 4-> O Glyptocephalus unidentified § *H r—i 03 QJ G U O G G CJ CQ x: 0 CQ PQ Pleuronectidae (cont. TABLE 30 CO CTn o r-H O o o 00 03 CO CO CJN 00 >>d- CA cn O'* r—i X CO CO i—i CO 00 r—i 1980; 00 cc 1980 OJ CT\ O'* o> ** r—i r—i r—i r—H 00 1984 co 1984 g co r^- C/3 CO G jG - *• G *. ON G 3 u O *-♦—I X (J X X* (J (j Cm co •X G G co G G co CO •H G G CJ o O •H O O m. •H •H o Pm x cj Fiscus, O rO Fiscus, PQ PQ PQ r~~i CQ PQ X x cj CJ X CJ CJ 03 X X CJ G CJ >x »-} G XJ X C G X) LeBeouf, 03 ►X LeBeouf, . • * 03 X 03 03 and and O TO X X X) CJ X X w CO CO G 1874-1984. G co C c co CO CJ •H c C CJN 03 03 •H 03 03 G *H •H 03 and QZ r—4 r—t 03 and , r—i JZ r-H r—i ZD CJ X X CJ X X only) O CJ CJ M> O G ** ' H •H G •H •r4 *r_) G G • H U? O >. X X O XJ X CJ O O X X X CJ g G 4-> G G X X X G G G 3 O O G O O o G c < o O X CJ CJ < CJ CJ 2m CJ < < Condit Condit CJ Antonelis Antonelis stomachs angustirostris frcm remains Mirounga prey contents stomach restricted to the are of xn CO G listed CO •H o CJ r—i X PX 03 CO X accounts >> CO CJ G CJ X CO . *H X X • r—i r—i c px o CO ex aj 03 CJ o 03 G G CO CO X CJ U CJ G borealijaponicus CJ 1 X X calyx O sp. •H CO (Citings CJ CO X CJ CO CO 03 '—✓ o X CJ X CJ 03 *H 03 -H •H G G a 03 •H r-H X X X G G 03 revious U X 1 • X CO ps 03 •H X •H X X P co PX PX CO CO •H «H 03 cj a X G G G G 3) X cj CO CO • r~i • H G G ex 03 o X CJ x CO CO X X uthis o 03 X G X G X X * r-i - X CJ CO CO PX G G a, 03 •H o CJ o CJ o o CM 5. 00 03 G G o O CJ CJ o •H G X -H X a px G X X X r—i CO •H *H X X X X O X o o o * r-i •H 03 03 03 03 CO 00 r-i •H CO 03 O O XJ (X x X G x c G G C jz x O •H O X -H o u u 03 px X 03 O o O o u o H X CO w X o o H G O Chiroteuth CJ CJ o *H o O o >> 2G Onychoteuthis Chirote (cont. u O TABLE CJ CO o O G o Chiroteuthidae 31 O CO CT\ 00 CO i—1 i—i 1—1 cn w d 4-1 m a 3 3 W 0 •H 1 o 8 1d cn . 1CO (Q ■H i—1 -p -P CD •H ■H g rg 'd 0 only) c e -p 0 0 c u u 1874-1984. , stonachs from remains angustirostris prey to Mirounga IS stomach a) Cfi CD restricted s •H tn the of are o l •H jd o accounts U I u (Citings o *H Previous U] (D m 4) cd -H T3 -P - 5. 1 I—I 31 o Ia. §1 -p B8 (cont. 8 TABLE $ a 32 4-1 o CO +J 4-) S LO CO o cr -C O ^ ■Pco CQ to a) -H CO in o fg T— o M i—I o o 44 tO o o cou S 6 m m 8J d CD 0) +3 Ia cos o o CD CD otn •H in in s 3 cd co e -HCO | o o co CO (mm) 5 o tn 14 g 44 in m ■H CO rd id length ■s Igt Q tO o o id id hood m in d cd Upper n o o •H6 cd cd «o 3 a in ■c m o B & in in ■a-g 'd o o ■cV. o S4 in o & o in o in CO II g 3 fd * § E- ip V 5 ■O"' JO Q- n S.S E CD "co CO V & o -c CO CL o xr Q. -C E ■O' pfi o 0) o CO qJ i—I O CO CO t-3 O m ■Q in co E -* cd O Uo CD O co m o o co <~ I i cd m o m o in H CM C\l a jsqiunu ^B0g 33 o m B fi Sh 0 (years) Age (jeqiunu) sq;i|o;o 34 Southern Gonatopsis the or from magister angustirostris 5nm.) Berryteuthis of Mirounqa scale and a (probably squid beaks are on macrorhynchus gonatid the of view Globicephala unidentified an ventral from and stomachs of beak the (Dorsal in lower Bight found and ) upper The borealis California 3. FIGURE