8. Whaling Models for Cetacean Conservation
119
resolution by the IWC for the establishment of a whaling sanctuary in Southern
Hemisphere oceans. But protection might not be sufficient, and in many circumstances, conservation management must include intervention (Belovsky et al.
1994).
Interactions between whales and their prey and other competing taxa are largely
unknown. This fact must raise concerns about the utility of applying a singlespecies whaling model to species embedded in complex ecosystems (May et al.
1979). Sound ecosystem management requires that we confront this complexity in
resource management (Grumbine 1994; Boyce and Haney 1997). After all, application of the RMP can only occur in the context of a complex ecosystem.
One argument to support the “release-from-competition” hypothesis is that
despite protection since 1962 (Gambell 1976), Southern Blue and Humpback
Whales have not increased at rates that might have been expected (Schmidt 1994).
Yet, not until November 1993 was it learned that the USSR did not abide by their
IWC agreements to curtail whaling of Right, Blue, and Humpback Whales and
that the harvests of these species were seriously underreported (Yablokov 1994).
Given the weakness of understanding of the Antarctic ecosystem, justification for
whaling based on the competitive-release hypothesis easily could be challenged.
But if nothing is done, we are unlikely to improve our management.
Multispecies Context
The CLA is driven by a single-species population model; yet all whale populations are embedded in multispecies ecosystems. Interspecific interactions including competition and predation surely have consequences for the dynamics and
management of whale stocks. The complex dynamics that can emerge from multispecies and multistock systems would defy the existence of simple dynamic
equilibria as assumed by the CLA (May 1987; Botkin 1990). Of particular significance for the krill-based southern ocean stocks are the trophic-level interactions
between krill (Euphausia spp.) and whales and the competitive relations among
whales feeding on krill.
Competitive interactions among Antarctic species feeding on krill have
changed as a consequence of whaling earlier in this century (Horwood 1987).
Stocks of Blue Whales were depleted first, followed by heavy harvests of Fin
Whales. When Fin Whale stocks declined, an eruption of harvests of Sei Whales
occurred in Antarctic waters, presumably curtailed by the ban on whaling in 1986.
Only in recent years has a significant number of Minke Whales been taken from
Antarctic waters (Fig. 8.2).
Before whalers shifted from their focus to taking Sei Whales in the 1960s,
increased pregnancy rates and decreased age of maturity were documented for Sei
Whales, suggesting that they were prospering from reduced competition for krill
stocks resulting from depressed Blue and Fin Whale stocks (Gambell 1973).
Similarly, first age of maturity for Minke Whales has decreased since the 1930s
despite limited take of this species, again implying that the species is responding
119
resolution by the IWC for the establishment of a whaling sanctuary in Southern
Hemisphere oceans. But protection might not be sufficient, and in many circumstances, conservation management must include intervention (Belovsky et al.
1994).
Interactions between whales and their prey and other competing taxa are largely
unknown. This fact must raise concerns about the utility of applying a singlespecies whaling model to species embedded in complex ecosystems (May et al.
1979). Sound ecosystem management requires that we confront this complexity in
resource management (Grumbine 1994; Boyce and Haney 1997). After all, application of the RMP can only occur in the context of a complex ecosystem.
One argument to support the “release-from-competition” hypothesis is that
despite protection since 1962 (Gambell 1976), Southern Blue and Humpback
Whales have not increased at rates that might have been expected (Schmidt 1994).
Yet, not until November 1993 was it learned that the USSR did not abide by their
IWC agreements to curtail whaling of Right, Blue, and Humpback Whales and
that the harvests of these species were seriously underreported (Yablokov 1994).
Given the weakness of understanding of the Antarctic ecosystem, justification for
whaling based on the competitive-release hypothesis easily could be challenged.
But if nothing is done, we are unlikely to improve our management.
Multispecies Context
The CLA is driven by a single-species population model; yet all whale populations are embedded in multispecies ecosystems. Interspecific interactions including competition and predation surely have consequences for the dynamics and
management of whale stocks. The complex dynamics that can emerge from multispecies and multistock systems would defy the existence of simple dynamic
equilibria as assumed by the CLA (May 1987; Botkin 1990). Of particular significance for the krill-based southern ocean stocks are the trophic-level interactions
between krill (Euphausia spp.) and whales and the competitive relations among
whales feeding on krill.
Competitive interactions among Antarctic species feeding on krill have
changed as a consequence of whaling earlier in this century (Horwood 1987).
Stocks of Blue Whales were depleted first, followed by heavy harvests of Fin
Whales. When Fin Whale stocks declined, an eruption of harvests of Sei Whales
occurred in Antarctic waters, presumably curtailed by the ban on whaling in 1986.
Only in recent years has a significant number of Minke Whales been taken from
Antarctic waters (Fig. 8.2).
Before whalers shifted from their focus to taking Sei Whales in the 1960s,
increased pregnancy rates and decreased age of maturity were documented for Sei
Whales, suggesting that they were prospering from reduced competition for krill
stocks resulting from depressed Blue and Fin Whale stocks (Gambell 1973).
Similarly, first age of maturity for Minke Whales has decreased since the 1930s
despite limited take of this species, again implying that the species is responding