Vaquita.tv

Written by Sarah Mesnick – NOAA Fisheries, Southwest Fisheries Science Center

The vaquita first became known to the scientific community after the discovery of a bleached skull on the beach north of Punta San Felipe in Baja California Norte, Mexico, on 18 March 1950 by Ken Norris, then a graduate student at UCLA.

The following year two additional skulls were found and these three skull specimens formed the basis for the description of a new species of porpoise, Phocoena sinus, (Norris & McFarland 1958). While most of the early sightings at sea lack sufficient detail to determine if they were indeed P. sinus, the first observation with sufficient detail to be accepted is likely to be that recorded by Norris and McFarland (1958). The authors describe three small, wary animals with triangular dorsal fins that were briefly seen before submerging about 8 miles NE of San Felipe on 28 April 1955. Three decades would pass before there were sufficient specimens collected to describe the external morphology (Robles et al. 1986, Brownell et al. 1987).

Coincident with the initial scientific description of the new species was the realization that individuals were incidentally taken in the artisanal gillnet fishery for totoaba and shark and in the commercial trawl fishery for shrimp; the first reports of incidental catch of vaquitas in totoaba nets came from Norris and Prescott (1961), Flanagan and Hendrickson (1976), and Brownell (1982) and had probably been occurring since the 1930’s (Brownell 1982, Vidal 1995). While there was no systematic documentation of incidental mortality in the early years, concern over the species’ conservation status was expressed since the early years (IWC 1975).

As specimens were collected from incidental by-catch in fishing gear, studies of vaquita life history and ecology were conducted. The first data on feeding habitats, based on stomach content analysis, was published by Fitch and Brownell (1968) who found that vaquita feed on small, shallow-water, bottom-dwelling fishes. At the same time, he first study of vaquita life history (Hohn et al. 1986) suggested a lower rate of increase than for other porpoise population. A detailed review of all known records confirmed that the distribution was restricted to the extreme upper Gulf of California (Brownell 1986) and has the smallest geographical range of any cetacean.

Difficult to survey because of its small size and inconspicuous nature, several approaches have been used to estimate the abundance and population trends of vaquita.

The first systematic survey using a large research vessel and line-transect methods to estimate vaquita abundance and distribution was conducted in 1993 (Gerrodette et al. 1995). Meta-analysis of early surveys confirmed that the population numbered only a few hundreds of individuals (Barlow et al. 1997). Based on a joint Mexico-US survey in 1997, covering all known and suspected habitat of the species, Jaramillo-Legoretta et al. (1999) estimated 567 individuals (CV= 0.51, 95% confidence interval = 177–1073). Also in 1997, the International Committee for the Recovery of Vaquita (CIRVA) was created to develop, oversee and promote a science-based recovery plan for the vaquita. CIRVA focused conservation efforts on the need to eliminate unsustainable bycatch in fishing gear.

The only effort-corrected study to estimate vaquita incidental catch was conducted by D’Agrosa et al. 2000). Based on fisherman interviews and on-board observers, D’Agrosa’s et al. quantified the bycatch of vaquita per fishing trip in each of five types of gillnets from January 1993 to January 1994. The authors found that some level of vaquita bycatch is known to occur in most, if not all, types of gill nets used in this area. They extrapolated their bycatch rate to the total estimated number of trips from El Golfo de Santa Clara to be 39 vaquitas/year (95 percent confidence interval = 14–93. Including the estimated number of fishing trips from neighboring San Felipe, the estimate of total annual bycatch increased to 78–168 per year; bycatch rates that were considered unsustainable (D’Agrosa et al. 2000). Although fishery bycatch has been identified as the greatest risk factor for vaquita survival, other potential risk factors have been identified and reviewed. Rojas-Bracho and Taylor (1999) examined three risk factors (pollutants, loss of Colorado River input, and genetic inbreeding) and found that none would appreciably increase the risk of extinction and none would prevent the recovery of vaquita.

Over the next decade, the population was monitored acoustically based on systematic listening at fixed stations throughout the northern Gulf of California using an analog acoustic detector. These data revealed that the population was declining rapidly; the number of acoustic detections declined by 70% during the decade from 1997-2007 (Jaramillo-Legorreta & Rojas-Bracho 2008). These data agree with population estimates based on a modeling approach which projected the population forward from 1997 to 2007 and estimated that only approximately 150 vaquita remain (Jaramillo-Legoretta et al. 2007). It was clear from these studies that if no action was taken, vaquita are likely to decline to a level where extinction may be inevitable within the next two years.

The recently concluded Vaquita Expedition 2008 and subsequent workshops were an international effort to design passive acoustic techniques to provide a way for the government of Mexico to determine whether the current conservation actions to reduce gillnet mortality is successful.

References:

Barlow, J., T. Gerrodette, and G. Silber (1997). First estimates of vaquita abundance. Marine Mammal Science 13: 44–58.

Brownell, R.L., Jr. (1986). Distribution of the vaquita, Phocoena sinus, in Mexican waters. Marine Mammal Science 2: 299–305.

Brownell, R.L., Jr., L.T. Findley, O. Vidal, A. Robles, and N.S. Manzanillo (1987). External morphology and pigmentation of the vaquita, Phocoena sinus (Cetacea: Mammalia). Marine Mammal Science 3: 22–30.

D’Agrosa, C., C.E. Lennert-Cody, and O. Vidal (2000). Vaquita bycatch in Mexico’s artisanal gillnet fisheries: Driving a small population to extinction. Conservation Biology 14: 1110–1119.

Flanagan, C.A., and J.R. Hendrickson (1976). Observation on the commercial fishery and reproductive biology of the totoaba, Cynoscion macdonaldi, in the northern Gulf of California. Fishery Bulletin 74: 531–544.

Jaramillo-Legoretta, A.M., L. Rojas-Bracho, R.L. Brownell, Jr., A.J. Read, R.R. Reeves, K. Ralls, and B.L. Taylor (2007). Saving the vaquita: Immediate action not more data. Conservation Biology 21: 1653–1655.
Jaramillo-Legoretta, A.M and L. Rojas-Bracho, 2008.

Jaramillo-Legoretta, A.M., L. Rojas-Bracho, and T. Gerrodette (1999). A new abundance estimate for vaquitas: First step for recovery. Marine Mammal Science 15: 957–973.

Norris, K.S., and W.N. McFarland (1958). A new harbor porpoise of the genus Phocoena from the Gulf of California. Journal of Mammalogy 39: 22–39.

Norris, K.S., and J.H. Prescott (1961). Observations on Pacific cetaceans of Californian and Mexican waters. University of California Publications in Zoology 63: 291- 402.

Robles, A., O. Vidal, and L.T. Findley (1987). La totoaba y la vaquita. Información Cientifica Y Technológica 9: 3–6.

Rojas-Bracho, L., and A.M. Jaramillo-Legorreta (2002). Vaquita Phocoena sinus. Pp. 1277–1280 in W.F. Perrin, B. Wursig, and J.G.M. Thewissen (eds). Encyclopedia of Marine Mammals. San Diego: Academic Press.

Rojas-Bracho, L., and B.L. Taylor (1999). Risk factors affecting the vaquita. Marine Mammal Science 15: 974–989.

Rojas-Bracho, L., R.R. Reeves, and A. Jaramillo-Legoretta (2006). Conservation of the vaquita

Turvey, S.T., R. Pitman, T. Taylor, J. Barlow, T. Akamatsu, L. Barrett, X. Zhao, and R. Reeves (2007). First human-caused extinction of a cetacean species? Biology Letters 3: 537–540.

Vidal, O. (1995). Population biology and incidental mortality of the vaquita, Phocoena sinus. Report of the International Whaling Commission 16(Special Issue): 247–272.

Vidal, O., K. Van Waerebeek, and L.T. Findley (1994). Cetaceans and gillnet fisheries in Mexico, Central America and the Wider Caribbean: A preliminary review. Report of the International Whaling Commission 15(Special Issue): 221–233.