Phocoena sinus, Norris & McFarland, 1958

Russell A. Mittermeier & Don E. Wilson, 2014, Phocoenidae, Handbook of the Mammals of the World – Volume 4 Sea Mammals, Barcelona: Lynx Edicions, pp. 528-545 : 543

5.

Vaquita

Phocoena sinus

French: Marsouin de Californie / German: Kalifornien-Schweinswal / Spanish: Vaquita marina

Other common names: Cochito, Gulf of California Porpoise, Gulf Porpoise

Taxonomy. Phocoena sinus Norris & McFarland, 1958 ,

“from the northeast shore of Punta San Felipe, Baja California Norte, Gulf of California, Mexico.”

This species is monotypic.

Distribution. N Gulf of California (also called the Sea of Cortez) in N Mexico, the smallest known distribution of any marine cetacean.

Descriptive notes. Total length 120-150 cm; weight 30-48 kg. Few fresh specimens of the Vaquita have been measured fully and weighed. Dorsalfin is relatively tall for a porpoise ofthis genus (up to 15 cm, or c.10% ofthe total body length). Head is blunt, with little or no beak, as in other species of the genus. General body color is dark brownish-gray on back, fading to pale gray or white on belly. There are black patches around eyes and around lips. There is also a darker chin-to-flipper stripe. Neonates are born darker than adults and gradually get paler in color as they age. Tooth counts generally are 16-22 in each half of each jaw.

Habitat. Very specific habitat in the northern Gulf of California, although there are some suggestions the distribution of the Vaquita may have extended somewhatfarther south in the past, before it was badly depleted by gillnet fishing. The current range of the Vaquita is characterized by moderately shallow waters (mostly less than 40 m deep) just south of the mouth of the Colorado River. These waters are murky and sedimentladen. They are biologically very productive, with high chlorophyll levels, and can reach very high temperatures in summer and autumn.

Food and Feeding. The Vaquita appears to be an opportunistic feeder, eating a variety of small benthic and demersal fish species. Some cephalopods and crustaceans are also eaten. Although only a handful of stomachs have been examined to determine feeding habits, the Vaquita appears to feed mostly on several species of grunts and croakers ( Sciaenidae ). They also occasionally feed on squid (e.g. Lolliguncula ).

Breeding. Very little is known about reproduction of the Vaquita because there has only been a single study (using small samples) of its life history. Porpoises, in general, reach sexual maturity at 3-6 years of age, and females appear to give birth every other year (unusual for porpoises that usually have annual reproduction). Gestation is ¢.10-11 months. Breeding of the Vaquita appears to be strongly seasonal, with most births occurring in March-April. The oldest known Vaquita was 21 years old, but they may sometimes live a bit beyond this age.

Activity patterns. There have been no detailed studies of the behavior of the Vaquita, and all that has been learned comes from opportunistic sightings or those that occurred during other types of studies. Vaquitas are generally considered to be elusive and difficult to approach. They have a low, cryptic surfacing pattern that generally does not produce any splash or visible blow. They tend to stay many hundreds of meters away from large, motorized vessels, but they may occasionally approach smaller, idling vessels. When foraging, they generally surface 3-5 times and then perform a longer dive that may last several minutes. Their surfacing behavior is very unpredictable. They do not ride bow waves of boats and have never been observed breaching or performing other aerial displays.

Movements, Home range and Social organization. Essentially nothing is known of individual movements or home range patterns of Vaquitas because specimens have never been tagged. Photo-identification of individuals is possible, and although it has not been used much to date, such studies in the future may shed some light on this issue. Porpoises are generally observed alone or in small groups of 2-4 individuals (often consisting of several mother—offspring pairs). Vaquitas occasionally gather into large foraging aggregations that may consist of up to ten or more individuals, but these groups havelittle or no cohesion. These aggregations are presumably related to good feeding opportunities.

Status and Conservation. CITES Appendix I. Classified as Critically Endangered on The [UCN Red List. The Vaquita is also listed as endangered on nationallegislation in Mexico and the USA. It is currently considered by many to be the most endangered marine mammal species in the world. The entire population of the Vaquita was estimated at 245 individuals in 2008, and this represents a nearly 8% annual decline in numbers estimated by the same methods in 1997. If this decline has continued, then the Vaquita would number less than 200 individuals in 2013. There are a number of potential threats, but only entanglement in gillnets has been documented as the definite cause of death for most specimens examined. Until recently, the major culprit was the fishery for totoaba ( Totoaba macdonaldi , a sea bass found in the northern Gulf of California), but in the last couple of decades, other gillnetfisheries have become more prominent within the distribution of the Vaquita. Targets of these fisheries include several species of finfish, sharks, rays, and in particular shrimps. The Mexican government has embarked on an ambitious program to save the Vaquita, involving elimination of gillnetfishing within its distribution. New fishing gear (mini trawl nets) has been developed to replace gillnets that cause most mortality, but implementation has been slow. Mortality in gillnets continues, and it 1s uncertain whether it can be reduced to insignificant levels in time to save the Vaquita—the next 5-10 years will be critical. The new presidential administration in Mexico appears to be genuinely supportive of conservation of the Vaquita.

Bibliography. Barlow et al. (2010), D'/Agrosa et al. (2000), Gerrodette & Rojas-Bracho (2011), Gerrodette et al. (2011), Jaramillo-Legorreta (2008), Jaramillo-Legorreta, Rojas-Bracho, Brownell et al. (2007), Jaramillo-Legor reta, Rojas-Bracho & Gerrodette (1999), Jefferson & Curry (1994), Jefferson, Olson et al. (2009), Ortega-Ortiz et al. (2000), Rojas-Bracho & Fueyo (2010), Rojas-Bracho & Jaramillo-Legorreta (2009), Rojas-Bracho & Reeves (2013), Rojas-Bracho & Taylor (1999), Rojas-Bracho et al. (2006), Silber (1990, 1991), Silber & Norris (1991), Silber et al. (1994), Taylor & Rojas-Bracho (1999), Vidal (1990), Villa-Ramirez et al. (1993).

Figures

1. Indo-Pacific Finless Porpoise (Neophocaena phocaenoides), 2. Narrow-ridged Finless Porpoise (Neophocaena asiaeorientalis), 3. Spectacled Porpoise (Phocoena dioptrica), 4. Burmeister’s Porpoise (Phocoena spinipinnis), 5. Vaquita (Phocoena sinus), 6. Harbor Porpoise (Phocoena phocoena), 7. Dall’s 9 Porpoise. Phocoenoides. (null)

Distribution. N Gulf of California (also called the Sea of Cortez) in N Mexico, the smallest known distribution of any marine cetacean.