UNIT 23 

 MARINE MAMMALS OF THE PACIFIC REGION INCLUDING HAWAII 



Atoll. Additional populations, with limited rtpro- 

 diiction and maintained by immigration, are found 

 at Necker Island and Nihoa Island, and a small 

 number of seals are distributed throughout the 

 Main Hawaiian Islands. 



Demographically, the different island popula- 

 tions have exhibited considerable independence. 

 For example, abundance at French Frigate Shoals 

 grew rapidly from the 1950's to the 1980's, while 

 other populations declined rapidly. Current de- 

 mographic variability among the island popula- 

 tions probably reflects a combination oi different 

 histories and varying environmental conditions. 

 While management activities and research focus 

 on single island and atoll populations, this species 

 is managed as, and considered to be, a single stock. 



In the last two centuries, this species has expe- 

 rienced rwo major declines which, presumably, 

 have severely reduced its genetic variation. The 

 tendency for genetic drih may have been (and may 

 continue to be) relatively large, due to the small 

 size of the different island and atoll populations. 

 However, 1 0- 1 5% of the seals migrate among the 

 different populations and, at least to some degree, 

 this movement should counter the development 

 ot separate genetic stocks. 



Population Size 



Abundance of the Hawaiian monk seal in 1997 

 was estimated bv counts of individual seals, the 



relationship between beach counts and total popu- 

 lation size for subpopulations at Necker and Nihoa 

 Islands, and a "best guess" for the Main Hawaiian 

 Islands. A total of 1,295 seals (including pups) were 

 observed at the main reproductive populations in 

 1997. Estimates for Necker and Nihoa Islands (± 

 standard deviation) are 65 (+15.1) and 56 (±21.1), 

 respectively. Finally, sporadic reports indicate that 

 abundance on the Main Hawaiian Islands may be 

 as high as 40 seals. 



By applying NMFS guidelines tor assessing 

 marine mammal stocks, which account tor uncer- 

 tainty in our abundance estimates, the minimum 

 size tor the entire Hawaiian monk seal population 

 in 1997 was 1,423 seals. 



Current Population Trend 



Between 1958 and 1993, average beach counts 

 at the main reproductive population sites declined 

 Liy 60%. From 1985 to 1993, the total of the av- 

 erage site count declined by about 5'!i) annually. 

 From 1993 to 1997, the total remained relatively 

 stable (Figure 23-1). In the near future the trend 

 will likely be determined by the extent to which 

 expected growth at Kure Atoll and Pearl and 

 Hermes Reef will offset the expected further de- 

 cline at French Frigate Shoals. 



Human-induced mortality has caused two 

 major declines ot the Hawaiian monk seal, and it 

 ma\- continue to be an important tactor impeding 



Species 



StocI' area 



Potential 

 Minimum biological Annual 



population removal human- 



estimate level caused Strategic ESA 



(N I' (PBR)- mortality^ status^ status- 



Blue whale 

 Fin whale 

 Bryde's whale 

 Sea otter* 

 Sea otter^ 



Hawaii 



Hawaii 



Hawaii 



California 



Washington 



Table 23-1 



Continued from the previ 

 ous page. 



^Nmin IS a conservative estimate of abundance used to estimate PBR and orovides reasonable assurance that the stock size is equal to or greater 

 than the estimate Calculations are from 1996 N/A = information is not available 

 'PBR (potential biological removal) is the maximum number of animals, not including natural mortalities, that may be removed from a stock while allowing 



that stock to reach or stay at its optimum sustainable population level 150-100% of its carn/ing capacity) Calculations are from 1996 

 'Annual human-caused mortality is an estimate of the total number of annual mortalities and serious iniuries (likely to result in death) caused by humans 



Annual records for each species are not available Estimated totals are based upon available records, which vary by species (Barlow el a! . 1997) 

 ""Strategic status Y = yes, N = no 



^ESA status E = listed as endangered, and T = listed as threatened under the Endangered Species Act 

 ^his species is under the jurisdiction of the U S Fish and Wildlife Service, and is not included in the stock-status tables of the National Overview 



239 



