GRAY WHALES AND TRANSIENT ORCA MORTALITY
Dear Gray Whale friends,
It is almost impossible to watch the video of the pack of transient orcas attacking a mother and calf in Monterey Bay recently. And even harder to watch the desperate efforts of the mother to save her calf.
There can be no interference by humans to these horrific events which are part and parcel of the predator prey relationship which has existed in Nature and humanity since time immemorial. However, what is critical is the extent of predation and what impacts are being visited on the Gray Whale population.
Recent National Marine & Fisheries Service (NMFS) estimated a 35% mortality of calves and juveniles by transient orcas. This percentage, which is remarkably high, is based on a number of research efforts to monitor the kill. Monterey Bay and Unimak Pass in Alaska are the major killing zones. Given the significant increase in whale numbers this year, the mortality of calves and juveniles is a sure certainty to meet 35% and higher.
With the ongoing loss of ice in the Arctic, transient orcas are able to move much further into Gray Whale habitat as the ocean is now far more accessible. There’s very little monitoring available from Russian scientists, and what is available points to major predation in Chukotkan waters.
Every year NMFS is required to set a quota for the Gray Whales as the species is listed under the Marine Mammal Protection Act. Known as the Potential Biological Removal,the PBR is, for all intents and purposes the number of whales that can be killed without impacting the population. The basis of the complex hypothesis which delivers the quota number requires accurate population estimates, reproductive rate, and the recovery status of the population. The PBR is a source of considerable criticism because the data on which NMFS bases their numbers is out-dated, unreliable with methodology constantly changing.
A major failure of the PBR is the refusal of NMFS to include transient orca mortality.
Combined with the use of highly outdated population estimates, and incorrect assumptions about the recovery factor NMFS set quotas (PBR) way too high for the Gray whale population. When this mortality is combined with the annual Russian slaughter of 140 whales, the question has always been – how does this population continue to thrive?
And for at least four or five years in the mid 2000’s, the numbers in the San Ignacio Laguna were very low, causing great concern about the population. Yet in the last two years we’ve seen major increases, more cows and calves and an apparently healthy and well fed population.
There’s been some bizarre behavior witnessed this year and I will give an update on San Ignacio whales in the not too distant.
But we can all be sure of one thing. Gray whales are without doubt the most mysterious, unpredictable, uniquely intelligent, extraordinary creatures.
Sue Arnold, CEO, California Gray Whale Coalition