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

and Schweigert, 1991; Rooper, 1996). Predators of herring spawn include birds,
invertebrates, marine mammals, and fishes.
While the rates of herring spawn consumption for the five avian predators are
approximations, our model suggests that these predators are a significant
component in the loss of herring spawn.
At the same time, the high consumption by gulls, shorebirds, and surf scoters
underscores the importance of herring spawn in the annual cycle of these species.
Herring spawn contributes to meeting energy requirements for both breeding and
migration.
(Bishop and Green 2001). Sea lions congregate in Berners Bay to exploit the Eulachon
spawning runs in April and Mayof each year (Sigler et al. 2004). Sea lions also take
herring during this time and throughout the year. Finally, Humpback Whales also prey
upon herring (NMFS 2005a). However, the total predation pressures exerted on herring
is not a new phenomenon. Indeed, two major predators, the Steller Sea Lion and
Humpback Whale, are currently ESA-listed so the predation pressure on Lynn Canal
Herring is probably less now than it was before these predators were depleted. In
conclusion, while predation is a constant factor in herring population dynamics, the cause
of the observed population collapse is primarily a result of overfishing and the
destruction of spawning areas.
E. Other Natural and Manmade Factors Affecting
Continued Existence
1. Changing Ocean Conditions
The warming of the oceans in recent decades is well documented (Behrenfeld et
al. 2006). This warming threatens to reduce the amount of phytoplankton and
zooplankton throughout the oceans. Lynn Canal Herring feed directly on plankton, so
continued oceanic warming will reduce the available food. A recent article in the journal
Nature analyzed the impact of warming ocean temperatures on phytoplankton abundance
(Behrenfeld et al. 2006).
Climate effects on ocean biology are documented here for nearly a decade of
satellite ocean colour measurements. It is also clear from the current analysis that
surface warming in the permanently stratified ocean regions is accompanied by
reductions in productivity. The index used here (MEI) to relate climate variability
to [net primary productivity] NPP trends does not distinguish natural from
anthropogenic contributions, but observational and modelling efforts indicate that
recent changes in [sea-surface temperature] SST are strongly influenced by
anthropogenic forcing. These observations imply that the potential transition to
permanent El Niño conditions in a warmer climate state would lead to lower and
redistributed ocean carbon fixation relative to typical contemporary conditions.
Such changes will inevitably alter the magnitude and distribution of global ocean
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