Parasites of Forage Fishes in the Vicinity of Steller Sea Lion (Eumetopias Jubatus) Habitat in Alaska

Abstract

ABSTRACT:Fish serve as intermediate hosts for a number of larval parasites that have the potential of maturing in marine mammals such as Steller sea lions (Eumetopias jubatus). We examined the prevalence of parasites from 229 fish collected between March and July 2002 near two islands used by Steller sea lions in Southeast Alaska and island habitats in the Aleutian Islands. Sea lion populations have remained steady in Southeast Alaska but have been declining over the last 30 yr in the Aleutian Islands. Even though the fish samples near the Southeast Alaska haul-outs were composed of numerous small species of fish and the Aleutian Islands catch was dominated by juveniles of commercially harvested species, the parasite fauna was similar at all locations. Eleven of the 20 parasite taxa identified were in their larval stage in the fish hosts, several of which have been described from mammalian final hosts. Four species of parasite were more prevalent in Southeast Alaska fish samples, and seven parasite species, including several larval forms capable of infecting marine mammals, were more prevalent in fish from the Aleutian Islands. Nevertheless, parasites available to Steller sea lions from common fish prey are not likely to be a major factor in the decline of this marine mammal species.

Applying the tools of ecological immunology to conservation: a test case in the Galapagos sea lion

“…Juveniles at this stage of development spend less time in the colony and consume more prey (Mueller et al ., ). As prey items are likely to contain parasites (Moles & Heintz, ), this behavioural transition could increase net exposure to immunostimulatory molecules and lead to an increase in circulating IgG. This may explain the increase in IgG observed in the control colony.…”

“…It is interesting that eosinophil concentrations are elevated in both colonies in 24‐month‐olds. This could be due to increased exposure to macroparasites in prey (Moles & Heintz, ), as juveniles begin to forage more independently at this age (Jeglinski et al ., ). For example, pinnipeds acquire lung worm Parafilaroides decorus infections when they begin feeding independently (Smith, Skilling & Brown, ), and lung worm have been observed in dead 24‐month‐old Galapagos sea lions (Acevedo‐Whitehouse, unpublished data).…”

Nematode Parasites of Rockfish (Sebastes spp.) and Cod (Gadus spp.) from Waters near Kodiak Island Alaska, USA

“…Hysterothylacium sp. has been found in 19 fish species from Alaskan coastal waters [19][20][21][22][23][24][25][26][27][28][29]. Clearly, these parasitic nematodes are common in many species of host fish in this area; however, quantitative studies, such as ours, are lacking [1].…”

“…All three species of parasitic nematodes that we observed in our study have previously been documented in multiple species of host fish in Alaskan waters. Anisakis simplex has been documented in G. chalcogrammus and in at least four other fish species in Alaskan coastal waters [19][20][21][22][23][24][25][26][27][28][29]. Pseudoterranova decipiens has been documented in nine species of fish in Alaskan waters [19][20][21][22][23][24][25][26][27][28][29].…”

“…Anisakis simplex has been documented in G. chalcogrammus and in at least four other fish species in Alaskan coastal waters [19][20][21][22][23][24][25][26][27][28][29]. Pseudoterranova decipiens has been documented in nine species of fish in Alaskan waters [19][20][21][22][23][24][25][26][27][28][29]. Hysterothylacium sp.…”