It’s whale migration time. Beachgoers may have noticed the heart-shaped exhales that mark gray whales’ migration toward the Baja lagoons to give birth and mate. Several hundred are thought to be in the Channel at the moment — a busy whale-way. But there are varying perspectives on the long-term health of our local population of grays. What’s it all about?
Last month, the Eastern North Pacific population of gray whales lost a petition to the National Oceanic and Atmospheric Administration requesting a status review. The California Gray Whale Coalition had hoped to redesignate the local stock as “depleted,” meaning it is “below its optimum sustainable population (OSP).”
OSP with respect to any population stock is defined as “the number of animals which will result in the maximum productivity of the population or the species, keeping in mind the carrying capacity of the habitat and the health of the ecosystem of which they form a constituent element.” For each threatened population, the National Marine Fisheries Service, under NOAA, tries to determine a carrying capacity absent human exploitation, since it doesn’t have an accurate way to determine historic carrying capacity.
The briefest biography of modern grays includes their listing in 1970 under the Endangered Species Conservation Act, the ESA’s precursor. This provided sufficient protection that in 1994 the NOAA determined that the ENP grays were no longer in danger of extinction, and unlikely to become depleted in the foreseeable future. Accordingly, they were delisted.
The ENP grays passed a five-year review in 1999. The finding was based on an estimated population of more than 20,000 and a 2.5 percent annual population increase. A 2001 report reached the same conclusion.
Last year, the California Gray Whale Coalition petitioned the NMFS to redesignate the ENP gray whales as a depleted stock as defined in the Marine Mammal Protection Act. Such a designation would require the preparation of a conservation plan to restore the stock to a sustainable population.
The original listing and delisting were based on the scientific analysis of technical questions. Accordingly, the petition and the responses were more inclined to discuss tails of distributions than tails of whales. The petition disputed both the NOAA’s acceptable abundance levels and estimates of the current population.
The NMFS disputed these findings, in part because determining a pre-exploitation population figure isn’t possible. The petition did result in one change: The NMFS proposes to factor habitat degradation and restoration into their determination of future OSPs.
I suppose it’s mixed news. The great news is that the Eastern North Pacific gray whale’s population apparently hasn’t plummeted. The bad news is the continuing concern that a population plummet, from climate change food stresses, ship traffic or any of a number of changing factors, might be discernible only after the fact.
Slogging through the report gave me a fresh appreciation both for the difficulty of achieving sustainable populations in a degraded habitat, but also of making that assessment. If we can determine how to exist without imperiling the existence of our fellow Earth and sea travelers, we will have taken a giant leap toward our own population survival into the foreseeable future.
— Karen Telleen-Lawton’s column is a mélange of observations supporting sustainability. Graze her writing and excerpts from Canyon Voices: The Nature of Rattlesnake Canyon at www.CanyonVoices.com.