The Decline and Fall of the Pribilof Fur Seal (Callorhinus ursinus): A Simulation Study

1989 ◽  
Vol 46 (8) ◽  
pp. 1437-1445 ◽  
Author(s):  
Andrew W. Trites ◽  
Peter A. Larkin
Keyword(s):  
North Pacific ◽  
Survival Rates ◽  
Commercial Fishing ◽  
Juvenile Survival ◽  
Callorhinus Ursinus ◽  
Adult Males ◽  
The North ◽  
Adult Females ◽  
Fur Seal ◽  
The North Pacific

A mathematical model incorporating the basic life history features of the North Pacific fur seal (Callorhinus ursinus) approximated the decline of the Pribilof Islands population by reconstructing pup estimates and counts of adult males over the period 1950 to 1987. Simulation results suggest that commercial female harvesting and a series of poor juvenile survival rates were responsible for causing and maintaining the observed decline in pup production on St. Paul Island from 1956 to 1970. A more recent drop in pup production since 1976 is also attributed to poor juvenile survival, but with the addition of higher natural mortalities of adult females. It appears that the natural mortality of adult females may have increased by 2 to 5% beginning in the mid 1970s. We suspect reductions in the fur seal food base and entanglement-related mortality associated with commercial fishing in the North Pacific are contributing to the current decline, although neither possibility has yet been clearly demonstrated.

scholarly journals The Fur-Seal Herds of the North Pacific

Nature ◽  
1899 ◽  
Vol 60 (1554) ◽  
pp. 354-356
Author(s):  
R. L.
Keyword(s):  
North Pacific ◽  
The North ◽  
Fur Seal ◽  
The North Pacific

Trophic relationships of albatrosses associated with squid and large-mesh drift-net fisheries in the North Pacific Ocean

1997 ◽  
Vol 75 (4) ◽  
pp. 549-562 ◽  
Author(s):  
Patrick Gould ◽  
Peggy Ostrom ◽  
William Walker
Keyword(s):  
Pacific Ocean ◽  
Trophic Level ◽  
North Pacific ◽  
Marine Mammals ◽  
North Pacific Ocean ◽  
Transitional Zone ◽  
Trophic Relationships ◽  
Commercial Fishing ◽  
The North ◽  
The North Pacific

The diets of Laysan (Diomedea immutabilis) and black-footed albatrosses (D. nigripes) killed in squid and large-mesh drift nets in the transitional zone of the North Pacific Ocean were investigated by examining the contents of the digestive tracts and determining δ13C and δ15N values in breast-muscle tissue. The results show that (i) the combined prey of the two species of albatross consists of over 46 species of marine organisms including coelenterates, arthropods, mollusks, fish, and marine mammals; (ii) both species supplement their traditional diets with food made available by commercial fishing operations (e.g., net-caught squid and offal); (iii) while obtained from drift nets, diets of nonbreeding Laysan and black-footed albatrosses are dominated by neon flying squid (Ommastrephes bartrami); (iv) in the absence of drift-net-related food, Laysan albatrosses feed most heavily on fish and black-footed albatrosses feed most heavily on squid; and (v) based on δ15N values, nonbreeding adult Laysan albatrosses from the transitional zone of the North Pacific Ocean and Laysan albatross nestlings fed by adults from Midway Island in the subtropical Pacific feed at one trophic level and one-third of a trophic level lower than black-footed albatrosses, respectively.

scholarly journals The fur seals and fur-seal islands of the North Pacific ocean / By David Starr Jordan, [et al.]

1898 ◽  
Author(s):  
George Archilbald Clark ◽  
David Starr Jordan ◽  
Leonhard Stejneger ◽  
◽  
Keyword(s):  
Pacific Ocean ◽  
North Pacific ◽  
North Pacific Ocean ◽  
The North ◽  
Fur Seals ◽  
Fur Seal ◽  
The North Pacific

scholarly journals The fur seals and fur-seal islands of the North Pacific Ocean.

1898 ◽  
Author(s):  
◽  
George Archilbald Clark ◽  
W. W. Duffield ◽  
David Starr Jordan ◽  
Frederic A. Lucas ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
North Pacific ◽  
North Pacific Ocean ◽  
The North ◽  
Fur Seals ◽  
Fur Seal ◽  
The North Pacific
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