Migration of Bering Sea Herring and the Status of Herring Stocks at Nelson and Nunivak Islands. Regional Information Report 5J91-05 Alaska Department of Fish and Game, Juneau, Alaska.

Abstract

The Dutch Harbor food and bait fishery harvests migrating herring stocks enroute from spawning grounds to offshore wintering grounds. The following information summarizes what is known about the origin of herring caught in the Dutch Harbor food and bait fishery:
1. Several stock separation studies have indicated that the origins of the herring caught in this fishery are predominantly from the Togiak stock, averaging 78% Togiak over all studies.
2. The composition of the non-Togiak component of the harvest cannot be identified as to origin. Possible stocks contributing to the non-Togiak component include Norton Sound, Cape Romanzof, Nunivak Island, Nelson Island, Cape Avinof, Goodnews Bay, Security Cove, Port Moller, and possibly other Alaska Peninsula or other stocks. An estimate of the composition of the non-Togiak component is best made by using the relative biomass of the non-Togiak stocks.
3. In 1989, the Alaska Department of Fish and Game conducted a detailed examination of a single sample taken from one trawl haul from the groundfish fishery and of a single sample taken from one purse seine in the Dutch Harbor food and bait fishery. This study indicated that the schools from which the two samples were selected represented a segregated age-size composition, and had a larger component of non-Togiak herring than would be expected if herring from all areas were randomly mixed. However, the overall result of this study showed that Togiak stocks dominated (78%) the Dutch Harbor harvest, agreeing with earlier stock separation studies conducted by the University of Washington. The finding of segregated age-size compositions does not change the overall stock composition estimates, but increases the variability of predicted of stock composition estimates.
4. Herring from Nelson Island likely overwinter with other eastern Bering Sea herring stocks in the area north and west of the Pribilof Islands. Both a clockwise, coastal route around Bristol Bay and a counterclockwise, distinct offshore route to the wintering grounds have been hypothesized for the Nelson Island stock. No convincing evidence exists to suggest that the Nelson Island herring stock follows one route or the other. If Nelson Island herring migrate via the counterclockwise, direct offshore route, they would not be taken in the Dutch Harbor food and bait fishery. If Nelson Island herring migrate via the clockwise, coastal route, the relative biomass of eastern Bering Sea herring stocks is the best available predictor of the composition of a late summer Dutch Harbor food and bait fishery.
5. Swimming speed analyses suggest that if Nelson Island herring migrate clockwise, they would not arrive at Dutch Harbor until at least early August, and perhaps as late as mid-September. Togiak herring are known to arrive at Dutch Harbor by mid-July. This suggests that a mid-July fishery at Dutch Harbor could avoid Nelson Island herring. Previous scale pattern analyses were not capable of detecting any meaningful trend in the proportion of non-Togiak stocks over time.