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

each a critical energy level of 3.0 kJ/g in about 87 days. This lipid buffer
provides a nominal 3-month bridge (December–February) to the beginning of the
following year’s production cycle but with little margin for error. The possibility
that juveniles also supplement their energy stores by feeding opportunistically
during the winter was examined by Foy and Paul (1999). They found that
although there was evidence for limited feeding, the amounts ingested were
apparently insufficient to account for winter metabolic demands. On the basis of
these empirical observations, we concluded that the winter period of plankton
diminishment imposes measurable bioenergetic constraints on the survival of
juvenile herring and their eventual recruitment to the adult stock in PWS.
(Cooney et al. 2001).
In addition to the threat of starvation, changing ocean conditions may cause
herring to grow too large for the ecosystem to support them. Studies in Alaska have
shown that elevated temperatures associated with El Nino can accelerate growth rates to
the point that the herring do not have sufficient energy to successfully over-winter and
spawn, particularly if food is also in short supply due to elevated temperatures (Salazar
and Salazar 2002).
The effects of warming ocean temperatures on the closely related Atlantic Herring
is relevant to Lynn Canal Herring. For the Norwegian population of Atlantic Herring,
Engelhard and Heino (2006) described the effects of climate and environmental variables
on reproduction. The researchers determined that higher water temperatures and
associated poor food availability caused herring to skip reproduction for that year
(Engelhard and Heino 2006).
The extent to which herring may skip reproduction was found to be not only
related to fish size and condition but also to climatic factors.
Notably, colder sea temperatures (possibly associated with a negative NAO
index) favoured both adult survival and participation in the second spawning
season (Table 3). Prey availability is a possible mechanism for this. The copepod
Calanus finmarchicus, a key species in the Norwegian Sea ecosystem, is the most
important prey species for adult herring during the summer feeding season
(Dalpadado et al. 2000). There is an inverse relationship of C. finmarchicus
abundance with the NAO and sea surface temperatures (Fromentin and Planque
1996).
The possibility of contrasting climate effects on juvenile and adult herring has
interesting population implications. Usually, variations in survival early in life far
exceed those in adults, so that the relationship of overall stock abundance with
temperature will still follow that of juveniles (in agreement with Toresen and
Østvedt 2000). Despite this, the inverse temperature effect on adult herring
survival and skipped reproduction remains relevant, as it is directly linked to the
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