But the question of how often new estimates or indices must be obtained to monitor trends is a tricky one. Ship surveys are expensive and they cannot be expected to detect population declines or increases on an acceptable timescale for such a critically endangered species. According to one analysis, a single survey in 2006 or 2007 would have a probability of only 11% of detecting a 3%/year decline and a 16% probability of detecting a 10%/year decline. Achieving an acceptable probability (e.g. 95%) of detecting a 3% decline would require annual surveys over a period of 39 years at a cost of approximately $29 million. Moreover, by that time (c. 45 years from now) only some 180 or so vaquitas would be left. Clearly, it is wiser to invest available funds in conservation actions, particularly in ones that offer viable socioeconomic alternatives to fishermen.
Mexico has a very good record in helping endangered marine mammals to recover. There are no better examples anywhere in the world than eastern Pacific gray whales and northern elephant seals, both of which came back from low numbers and now represent true conservation success stories. Similar efforts are needed urgently for the vaquita, a small animal living in a small area with a small
Source:Blackwell Publishing Ltd.