Randall R. Reeves

First human-caused extinction of a cetacean species?

The Yangtze River dolphin or baiji (Lipotes vexillifer), an obligate freshwater odontocete known only from the middle-lower Yangtze River system and neighbouring Qiantang River in eastern China, has long been recognized as one of the worlds rarest and most threatened mammal species. The status of the baiji has not been investigated since the late 1990s, when the surviving population was estimated to be as low as 13 individuals. An intensive six-week multi-vessel visual and acoustic survey carried out in November–December 2006, covering the entire historical range of the baiji in the main Yangtze channel, failed to find any evidence that the species survives. We are forced to conclude that the baiji is now likely to be extinct, probably due to unsustainable by-catch in local fisheries. This represents the first global extinction of a large vertebrate for over 50 years, only the fourth disappearance of an entire mammal family since AD 1500, and the first cetacean species to be driven to extinction by human activity. Immediate and extreme measures may be necessary to prevent the extinction of other endangered cetaceans, including the sympatric Yangtze finless porpoise (Neophocaena phocaenoides asiaeorientalis).

Whaling as Science

In an open letter published last year in the New York Times, 21 distinguished scientists (including three Nobel laureates) criticized Japan’s program of scientific research whaling, noting its poor design and unjustified reliance upon lethal sampling. In a recent Forum article in BioScience, Aron, Burke, and Freeman (2002) castigate the letter’s signers and accuse them of meddling in political issues without sufficient knowledge of the science involved in those issues. As members of the Scientific Committee (SC) of the International Whaling Commission (IWC), we can attest that the signers of the open letter correctly summarized criticisms made by researchers very familiar with Japanese

Global Climate Change and Marine Mammals

The global climate is changing, at least in part because of human-generated emissions of ozone-depleting substances (Ashmore and Bell, 1991; United Nations Environmental Program, 1987, United Nations Environmental Program, 1993; Intergovernmental Panel on Climate Change, 2001a, Intergovernmental Panel on Climate Change, 2001b, Intergovernmental Panel on Climate Change, 2001c), world-wide use of hydrocarbons responsible for emissions of greenhouse-effect gases (Flavin, 1992; Wellburn, 1994), and largescale deforestation and desertification (Barbier et al., 1994). Predictions for the world’s oceans range from little or no change to partial melting of Arctic and Antarctic loose ice and shelves, with concomitant rises of sea levels. While many “alarmist” scenarios have been proposed, it is generally accepted that in the next 100 years, sea temperatures will rise by about 1.3-5.8°C and overall sea level will rise by anywhere from 9 to 88 cm (Intergovernmental Panel on Climate Change 2001a). Because of the overall global change, there are likely to be more local fluctuations in rainfall, storm frequencies, and the incidence of abrupt cold and dry spells, along with other mesoscale changes. Hurricanes and typhoons are known to form with greater frequency when water temperatures are at or above 28° C, and even short-term changes in climate (for example, El Nino Southern Oscillation events, ENSOs) can affect the incidence and severity of such storms. This generally grim scenario could be improved if the present decline in ozone-depleting emissions were to continue, or if energy substitutes for fossil fuels were more fully developed and widely adopted (Moore et al., 1996, Intergovernmental Panel on Climate Change, 2001c).

U.S. seafood import restriction presents opportunity and risk

Marine mammal protections require increased global capacity On 1 January 2017, the U.S. National Oceanic and Atmospheric Administration (NOAA) will enact a new rule (1) requiring countries exporting seafood to the United States to demonstrate that their fisheries comply with the U.S. Marine Mammal Protection Act (MMPA). The United States is the worlds largest seafood importer (2); the MMPA is among the worlds strongest marine mammal protection laws; and most of the worlds ∼125 marine mammal species are affected by fisheries bycatch (accidental entanglement in fishing gear) (3). This regulation could thus have significant conservation benefits, potentially spilling over to other areas of marine governance, if it is accompanied by substantial investments to boost scientific and compliance capacity in developing countries. Otherwise, it risks having little effect besides inflicting economic hardship on already poor communities.

A retrospective investigation of two dolphin mass mortality events in Iran, autumn 2007

Abstract During the autumn of 2007, two mass mortality events involving at least 152 small cetaceans were reported from southern Iran. Both events occurred on the Gulf of Oman coast near the town of Bandar Jask, and were separated by a month in time and more than 170 km in distance. The first event, on 20 September 2007, involved 79 animals, probably all Spinner Dolphins (Stenella longirostris). Dead animals, all exhibiting a similar degree of decomposition, drifted to shore along 13 km of coastline over a period of approximately 24 hours. These circumstances suggest that the mortality was caused by a single acute event at sea. Several carcasses had evidence of traumatic injuries, the stranding event was spatially and temporally coincident with an active fishing ground, and other potentially bycaught and discarded species were found on the beach. This pattern is generally consistent with the hypothesis that the Dolphin mortality was caused by fishing operations, although the available data are insufficient to confirm that hypothesis unequivocally. On 24 October 2007 there was a mass stranding of 73 live Striped Dolphins (Stenella coeruleoalba), a pelagic species believed to be rare in the Gulf of Oman. The most likely explanation for this mass stranding is that the Dolphin group was trapped by a falling tide among the complex sandbanks of the Kangan estuary. Striped Dolphins are not normally found in shallow water or near shore, and their occurrence in this area is considered unusual. The factor or factors that caused them to enter this atypical habitat remain unknown. The two mass mortality events involved different species and exhibited many different characteristics; there is no evidence to suggest that they were linked.

Population Status and Trends

Publisher Summary For marine mammals, status is a measure of the size or general health of a population relative to some management standard. A trend is a measure of the rate at which a population grows or declines over some time period. Inherent in the concept of status is the evaluation of populations relative to some standard or metric. Absolute estimates of population size may be included in an assessment of the population status, but an evaluation of status is incomplete without evaluating the significance of this population size relative to some goal. The standards for evaluating the status of populations are typically related either to a harvest or to a conservation objective. To evaluate harvest objectives, population size was evaluated relative to the population level (MSYL) that would give the maximum sustainable yield (MSY). Populations are expected to decline as a result of harvests, but as population size decreases, the population growth rate is expected to increase to compensate for this harvest. The goals of conservation efforts can range from preventing the extinction of species to returning populations to their carrying capacity level. The metrics used to measure the conservation status of populations range over this same spectrum. When populations become very small or are declining rapidly, their status is often determined by estimating the probability of extinction within a defined time period. An upward or downward trend in population size is obviously a significant component in evaluating the status of a population. Population trends have been directly estimated for only a tiny proportion of all cetacean populations. The primary problems are that population size cannot be estimated very precisely and population growth is typically slow.