FEATURE

When Steller sea lions was not decli ning in the area from (Eumetopias jubatus) were being southeastern Alaska through Ore- considered for listing as endan- The Steller Sea gon. gered or threatened under the U. S. Enda ngered Species Act Lion: Two Discrete The historical center of sea lion (ESA) in the late 1980s, there was Stocks? abundance is the Gulf of Alaska no evidence to support geo- and eastern . graphic stock separation for the Within that area, Steller sea lions species. Consequently, the spe- have been most abundant be- cies was listed as threatened tween the Kenai Peninsula and throughout its range even though data now are available to distin- Island (Kenai- Kiska) sea lion populations in some ar- guish discrete stocks. The analy- (Fig. 1). Counts of animals on eas were not at low levels or de- sis employs a phylogeographic rookeries and haul-out sites within clining. A significant management approach , using information on the Kenai- Kiska area have been issue resulting from the ESA list- distribution, genotype, pheno- used to monitor sea lion status ing of the Steller sea lion is the type, and population response to and trends in Alaska. These impact the Act's protective meas- define a stock. The analysis pro- counts indicated a rapid decline in ures are having on commercial vides evidence which suggests abundance between the 1970s fisheries, particularly the fisheries the existence of two discrete and 1989 and have continued to for Pacific salmon and North Pa- stocks of Steller sea lions, an show a decline but at a slower rate cific groundfish. eastern and western stock geo- from 1989to 1995 (Fig. 2). Asyet, graphically separated at approxi- the cause(s) for the decline has The ESA prohibitions on the take mately long. 144OW. Studies of not been identified. of listed species require the Na- mitochondrial DNA (mtDNA) pro- tional Marine Fisheries Service vide the strongest evidence of this Population dynamics (NMFS) to consider management geographic stock separation. The demography of Steller sea actions that reduce or eliminate Analysis of population demogra- lions in southeastern Alaska dif- take and which presumably en- phy also support the thesis, while fers from the demography of sea hance the probabi lity of a species tagging and branding studies sug- lions in other areas of Alaska. recovery. In the case of the Steller gest that Steller sea lions are re- The southeastern Alaska popula- sea lion, because of the animals productively faithful to their birth tion has declined only slightly, interactions with commercial fish- sites and that immigration rates whereas those populations to the ing activities, those management are low. west have declined substantially. actions can restrict the time and In 1995, NMML scientists con- area of fishery openings, reduce Introduction ducted a population viability allowable harvests, or curtail fish- The breeding range of the Steller analysis (PV A) using the number ing in areas that are designated sea lion extends from the Kuril of pups and adults counted from under the ESA as critical habitat Islands and Okhotsk Sea, east- 1975 to 1993 at Alaskan rookeries ward through the Aleutian Islands for Steller sea lions. Although and found that the probability of and Gulf of Alaska, and then south Steller sea lions in the United extinction of the Steller sea lion States are managed currently as to Ano Nuevo Island off central was much less for the southeast- a single population regardless of California (Fig. 1). The number of ern Alaska region (about 0. 1 at their geographic derivation , if sea lions throughout the range 1 00 years) compared with other separate stocks were to be identi- declined by over 600 /0 from about parts of the state (about 0.9 at 100 fied and managed separately, lo- 300,000 in the 1960s to about years). Whether these differ- calor regional management could 116, 000 in 1989, the year the Na- ences in probability of extinction be implemented based on the dy- tional Marine Mammal Laboratory are genotypic differences or namics of local or regional Steller (NMML) coordinated the first rather represent manifestations of sea lion populations. range-wide survey. The second different abiotic or biotic factors range-wide survey in 1994, also affecting the local populations is This article examines information coordinated by the NMML, indi- unknown. obtained before and after the Stel- cated a further overall decline; ler sea lion s original listing under however, the survey indicated A cluster analysis of the rates of the ESA to determine if sufficient also that the number of animals change in adult numbers ob-

AFSC Quarterly Report 75O

RUSSIA ALASKA

600

3 A\eU\\a. t\ \ S

450 Kenai - Kiska

Pacific Ocean 1440 W 300

135O 1800 135O Figure 1. The map depicts the range of Steller sea lions. Arrows indicate rookeries and the shaded areas represent the approximate distribution of sea lions when at sea. The Kenai Peninsula-Kiska Island area is also shown. served at rookeries in Alaska dur- Steller sea lion s migratory and Satellite telemetric studies were ing 1975-94 found consistent foraging behavior as well as natal conducted by NMML during the groupings of rookeries with com- site fidelity. In 1975 and 1976, past decade in both summer and mon trends. These groupings Alaska Department of Fish and winter on young-of-the-year and ranged from couplets of adjacent Game (ADF&G) biologists adult female Steller sea lions. rookeries (within 37 km of each branded 7 046 Steller sea lion These studies indicate that the other, e. Marmot Island and pups at six rookeries in the Gulf of marked animals forage from a Sugarloaf Island in the Gulf of Alaska. Brands were designed to central place and return to that Alaska) to groupings of five or indicate rookery and year of birth. place at the end of the trip, which more sites spread over several Since then, observers throughout may last from hours to months. hundred kilometers (e.g., Sugar- the Gulf of Alaska and southeast- The rookery is part of the central loaf Island to Atkins Island). The ern Alaska have reported sub- place, but the central place may implication of these groupings, stantial numbers of young, also include adjacent haul-out which persisted through periods immature, branded sea lions sites and perhaps a nearby rook- of population stability and decline, throughout Alaska. Some sea li- ery. Though the sea lion s winter is that shared environmental fea- ons had moved over 1 500 km foraging range is great, telemetric tures such as prey resources or from the branding site; young, im- data have shown that most ani- oceanographic conditions may af- mature animals were also re- mals return to the tagging location fect rookery demographics. Pup ported in the Gulf of Alaska that and not to another far-off site. counts at separate rookeries will were tagged as pups in British be examined using cluster analy- Columbia. Generally, yearlings Steller sea lions tagged by NMFS sis in the near future. and young animals 1-4 years of scientists in the Aleutian and Kuril age dispersed over great dis- Islands and by Russian scientists Tagging and branding tances. on the dis- Tagging and branding studies persed in similar ways (Fig. 3). have been used to examine the These studies indicated that sea

January-February-March 1996 ---.....(/) ...-...... -...... --...... ".....--.--...... -...... -..-...... ,..-...... -...... -...... ---...... --...... -...... -...-...... --...... -..--...... --.....-:::'&;"""""" ...... ,,"-..---- -.-..:...... """

lions dispersed less as they be- sighted at Sugarloaf Island in Genotypic data came sexually mature and tended 1976- 77 were branded there as Studies of mtDNA provide the to spend substantially more time pups in 1975-76. They also re- strongest evidence for stock near their birth sites when older. ported that of 15 recognizably separation in Steller sea lions. NMML scientists branded 800 branded females that gave birth at NMML biologists in collaboration pups (424 female, 376 male) with Marmot Island and Sugarloaf Is- with Texas A&M biologists exam- individual numbers at Marmot Is- land, only 1 gave birth at a rookery ined a segment (approximately land in 1987 and 1988, but the which was not its birth site. Less 450 nucleotide base pairs) of the size of the colony declined rapidly than 1 00/0 of the females marked mtDNA control region from 224 afterwards (through August 1994) by the NMML have been docu- Steller sea lion pups sampled at so, to date, only 21 of the 424 mented to breed elsewhere. I n all rookeries in Oregon most of females have been seen as cases, the females bred at rook- Alaska, and the Kamchatka Pen- adults. Of the 21 resighted fe- eries that were near their birth site insula and , males, all were observed as and that were part of the group . A phenetic analysis and adults on Marmot Island; 2 were identified in the cluster analysis distance matrix were also pro- seen without pups at Marmot Is- mentioned above using rates of duced. The study found nucleo- land in 1992 and then with pups at population change. Because of tide variability at 29 sites, which nearby Sugarloaf Island in 1994. these trends in site fidelity, ge- defined 52 haplotypes which were netic exchange between rooker- further grouped into eight mater- Branded males have been ies may be low. Consequently, nallineages. There was no com- sighted as subadults, in many the level of migration or gene flow mon haplotype that predominated parts of the range. An animal occurring between putative popu- throughout the range, but many marked at Rogue Reef in Oregon lation stocks (e.g., from Prince haplotypes occurred at low fre- was resighted at Marmot Island, William Sound to southeastem quency. Cluster analysis indi- Alaska; a male branded at Mar- Alaska) may be small. If gene cated that these lineages may be mot Island in 1977 was resighted flow between stocks is one or two subdivided into two genetically at in the eastem females per generation, which is differentiated populations, includ- Aleutian Islands in 1985; Marmot not unreasonable, it could be suf- ing an eastern population (Ore- Island males are commonly seen ficient to promote genetic isola- gon and southeastern Alaska) in southeastern Alaska in winter. tion. and a western population (Prince Whether these males will return to 100 their islands of birth to obtain a Rookeries only territory and reproduce (usually . All sites by 9 or 10 years of age) is ex- pected to be known in the next 3 80 years as they become physically and sexually mature. Once males are physically capable of obtain- ing a territory, they generally re- co 60 turn to the same territory ::s successive years, sometimes for .c: as many as 7 years. L.. 40 """""""""""""""""""""""""""""""'"""""""""""""""

Based on resightings of tagged ::s Steller sea lions, it appears that they are faithful to their birth site 20 ...... -...... -...... -...... -...... -.-.....--..."""-"""""""""-""""=r-' and that they generally return .a.- .....- there to breed, like other otariids. Although such resightings do not conclusively demonstrate natal site fidelity, they do suggest that 1975 1980 1985 1990 1995 site fidelity is a strong instinctive Survey Year behavior. ADF&G biologists re- ported that nearly 800/0 of the Figure 2. Counts of adult and juvenile Steller sea lions at rookeries and haul- branded sea lions that they out sites in the Kenai-Kiska area during June 1975-94.

AFSC Quarterly Report ...

William Sound and west). The av- ADF&G biologists found that age- Potential areas of research erage percent sequence diver- specific axillary girth , standard Parasites or groups of parasites gence among the 52 haplotypes length, and weight were all less have been used as biological tags was 70/0 (range 0. 80/0). Nu- during the 1980s than for animals to differentiate populations. The cleon diversity estimates for six of collected during the 1970s. lungworm Parafilaroides decorus the eight populations combined These data support the hypothe- may infect Steller sea lions only in was = 0.927, suggesting high sis that the decline in sea lion California. Sufficient samples levels of genetic diversity. Fur- numbers may be linked to prey have not been fou nd from areas ther, calculated gene flow esti- resources but provide no support- outside California to support a de- mates (Nem) , indicate about 9. ing data on geographic variation finitive conclusion. But intraspe- females per generation migrating in size. Age-specific size in differ- cific morphological variation to a nearby rookery (the move- ent geographic locations has not among Steller sea lions may ac- ment between stocks, as sug- been compared (other than for count for some of the lungworm gested above, is much lower). pups) because of insufficient species origi nally reported from data. these sea lions. This area of re- Similar mtDNA analysis were con- search has the potential for pro- ducted by University of California Population responsed data viding further evidence for the scientists on skin samples from Significantly higher levels of hap- existence of stock separation, but Steller sea lions from Ano Nuevo toglobin were found in Steller sea additional work is needed to de- Island, California, resulting in lion blood samples from the Aleu- termine if Steller sea lions from seven haplotypes, six of which tian Islands than in blood samples different parts of their range can were identical to those identified from animals in southeastern be differentiated by their para- from southeastern Alaska and Alaska. Haptoglobin is an acute sites. Oregon. One haplotype was phase blood protein that binds unique to Ano Nuevo Island. with hemoglobin to form a stable Determination of the levels of con- complex. Haptoglobin levels in- taminants (organochlorine pesti- Virtually no allozyme variation has crease in association with tissue cide residues, polychlorinated been detected by protei n electro- injury or other such stress (e. biphenals, and heavy metals)also phoresis perhaps because of lim- infection, trauma, inflammation). may be useful for discriminating ited geographic sampling. Blood The higher levels found in the between populations. There are and tissues from 157 sea lions Aleutian Island samples suggest at present no studies that com- were collected in the Gulf of that higher levels of injury or pare pollutant levels in Steller sea Alaska during 1975-77 by ADF&G trauma may exist there compared lions from different parts of the scientists. They studied 32 loci of with southeastern Alaska. range or that suggest that pollut- which 4 exhibited rare alleles. No ants are indicative of separate sea geographic variation was appar- Beta-endorphin levels in blood lion stocks. ent except for a possibly weak were analyzed from 30 sea lions differentiation of animals in Prince collected in the central Gu If of Conclusion William Sound. Alaska. Beta-endorphins are A synthesis of available data sug- morphine-like peptides produced gests that Steller sea lions qualify Phenotypic data by brain and pituitary tissue. They as a Category II population; ac- Animals from potentially separate have an analgesic property, which cording to the definition of Dizon stocks may differ in physical size. may influence the behavior and et al. (1992), Category II popula- Analysis of pup mass from the physiology of wild animals. How- tions require " that two (or more) Aleutian Islands (n=350), the Gulf ever, no significant differences populations/putative stocks coex- of Alaska (n=411), southeastern were found for beta-endorphin ist with total sympatry or with ex- Alaska (n=538), and Oregon levels among sampled animals. tensive geographical overlap or (n=245) obtained during 1987- The geographic area sampled be weakly defined in parapatry. indicates that a cline in pup mass may have been too small to detect Geographically there would be no exists. Aleutian Island pups were geographic variation in beta-en- reason not to manage them to- significantly heavier than pups dorphin levels. Existing data on gether, but critical differences in from the Gulf of Alaska and south- the timing of the breeding cycle behavior, morphology, genetics, eastern Alaska, and pups from and reproductive behavior show or some combination of these in- Oregon weighed less than pups no significant differences across dicate reproductive isolation to from any part of Alaska. the range. some degree." The strongest

January-February-March 1996 ~ ...... ~

RUSSIA

600

Bering Sea Sea of Okhotsk

"'I . 9 ~..lI~

Medny Island group Pacific Ocean billlliillrom:mn oz ova ape group 450 Kurillslands group

1500 1650 1800

Figure 3. Suggested preliminary dispersal scheme of Steller sea lions from birth to 4 years of age that were marked as pups at Russian rookeries. evidence for stock separation is that fewer than 100/0 emigrate. east of Cape Suckling, Alaska the mtDNA studies which indicate The large amount of mixing away (long. 144OW; Fig. 1), and a west- that an eastern and a western from rookeries during the non- ern stock, which includes all ani- stock exist with the division at breeding season is potentially mals at and west of Cape about Prince William Sound. confounding but may not result in Suckling. When sufficient data However NMML biologists rec- interbreeding between animals are available, particularly on the ommend additional genetic analy- from the two areas. The differ- genotype of Steller sea lions in the sis using protein electrophoresis ences noted in pup weights is tan- . Kuril Islands, recognition of addi- and nuclear DNA. Additional talizing and suggests the need to tional stocks may be appropriate. stocks may be identified in Russia finish cranial morphometric stud- and the Commander Islands once ies for which most of the measure- This article is based on the paper the entire area is sampled. The ments have been completed. Using the Phylogeographic differences observed in popula- Haptoglobin studies also provide Method to Identify Steller Sea tion dynamics and the site group- intriguing results supporting the Lion Stocks" by Thomas Loughlin ings resulting from the cluster two-stock concept for Steller sea of the NMML and was revised for analysis further supports the no- lions and should be pursued. the Quarterly Report by Susan tion of limited gene flow among Calderon of the AFSC Publica- rookeries (and stocks). Tagging In closing, NMML biologists rec- tions Unit. and branding studies show that ommend that Steller sea lions be Steller sea lions are reproduc- managed as two stocks, an east- tively faithful to their birth sites and ern stock that includes all ani mals

AFSC Quarterly Report