Petition to List Lynn Canal Pacific Herring under the Endangered ...

the commercial fishery in Lynn Canal has been closed; for 2001-2003, the spawning
biomass estimate was less than 1,000 tons and a more precise estimate for 2004 was 743
tons based on survey dives to measure egg density (M. Pritchett, pers comm). Along with
declines in biomass estimates, the geographic extent of the population’s spawning
grounds has also declined. From 1972 to 1989, herring spawn was observed in Auke Bay
in 14 out of the 18 years, or 78% of the time. However, 1989 was the last year that
herring spawn was observed in Auke Bay, and no spawning activity has been observed
south of Yankee Cove for the past 15 years (M. Pritchett, pers comm.). Based on the
information available, it seems likely that abandonment of the Auke Bay spawning
grounds was caused by a combination of factors, including increased shoreline
development in the bay, declines in water quality, and low numbers of herring available
to spawn and rebuild the stock (Wing, pers comm.,Koski, pers comm.). Continuing trends
in small population size and the lack of steady population growth despite the fishery’s
closure suggest that a population bottleneck may have occurred.
(NMFS 2005: 59). Similarly, the Alaska Dept. of Fish and Game has summarized the status of
the population in equally dire terms (ADFG 2004):
Prior to 1983, the Lynn Canal herring stock was one of the larger stocks in Southeast
Alaska supporting several commercial fisheries including a sac roe fishery, bait pound
fishery, and a winter food and bait fishery. Lynn Canal herring traditionally spawned
from Auke Bay to Point Sherman. This stock declined in 1982 and has since remained at
low and variable levels as evidenced from estimates of linear measurements of shoreline
that receive spawn. The reason for the decline is not clear, however, potential candidates
are overfishing, habitat degradation and/or disturbance in Auke Bay, geographic shifting
of spawning aggregations, population growth of major predators such as sea lions, or a
combination of these. If the decline is attributable solely to overfishing, it is puzzling
that there has been no apparent recovery or re-establishment of this stock during a 20-
year absence of exploitation. In other areas in Southeast Alaska, such as West Behm
Canal, herring stocks have grown from low levels to very high levels over a span of a few
years.
The documented spawn for the Lynn Canal herring stock from 1953 to 1981 ranged from
6 to 28 nautical miles averaging approximately 12 miles. Significant spawning occurred
in the vicinity of Auke Bay. In recent years however the entire Lynn Canal herring stock
has centered its spawn activity between Pt. Bridget and the Berners Bay flats. Since 1982
the documented spawn has ranged from 0.5 to 7 nautical miles averaging only 3.5
nautical miles. The established biomass threshold level for this stock is 5,000 tons of
spawning biomass. This means that before a herring fishery may be considered for the
Lynn Canal stock, a forecast spawning biomass must meet or exceed 5,000 tons. Based
on shoreline miles of spawn, it is estimated that the stock biomass has varied between
100 and 2,500 tons over the last 20 years. Studies of herring over-wintering in the Juneau
area have continued over the years in an attempt to reconcile acoustical observations of
biomass with estimates of spawning biomass, and to monitor age composition of the
stock.
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