TY - JOUR
T1 - Distribution and relative abundance of sperm whales in relation to key environmental features, squid landings and the distribution of other cetacean species in the Gulf of California, Mexico
AU - Jaquet, N.
AU - Gendron, D.
N1 - Funding Information:
Acknowledgements This study was funded by the Center for Field Research (Earthwatch, USA), Wildlife Conservation Society (USA), CONABIO (Mexico), and the ‘‘Société Académique Vaudoise’’ (Switzerland). CICIMAR-IPN, Mexico, and the University of Otago (New Zealand) loaned us equipment. We would like to extend special thanks to the skipper and owner of the research boat, John Botke, who lent us the sailing vessel and greatly helped with data collection, and to K. Babiak, L. Bertholet, J. Bourton, F. Dupont, K. France, D. Hauenstein, K. Hoelrich, G.King, D. McCutchen, F. Poma, C. Roelli, I. Ruiz-Castro, J. Smith, P. Sperisen, S. Thomas, R. Winjum and T. Worthen who helped us collecting the data at sea: Enrique Morales-Bojórquez provided us with the recent information on jumbo squid landing. This research was conducted under the scientific permit No. 040598–213–03 (1998) and 140598-213-03 (1999) from the Secretaria de Medio Ambiente Recursos Naturales y Pesca. The manuscript was much improved by comments from David Fletcher, Keith Jensen, Sarah Mesnick, Hal Whitehead and one anonymous reviewer.
PY - 2002
Y1 - 2002
N2 - Sperm whales (Physeter macrocephalus) feed predominantly on meso- and bathypelagic cephalopods for which effective sampling methods have not been developed. The Gulf of California is one of the very few areas where sperm whales might feed on a commercially fished species of squid (jumbo squid, Dosidicus gigas), presenting a unique opportunity to investigate the impacts of variations in jumbo squid abundance on sperm whale distribution. This study examines sperm whale distribution and relative abundance in relation to the distribution of D. gigas, other cetacean species and key environmental features over spatial scales ranging from a few kilometers to a several hundreds of kilometers. Data were collected during two field seasons in spring-summer 1998 and 1999 using non-invasive techniques. Landing statistics show that the jumbo squid fishery collapsed in 1998 and started recovering in early 1999. Despite this collapse in 1998, sperm whales remained abundant during both years, but there were strong differences in their aggregative behavior. In 1998, sperm whales were roughly evenly distributed, while in 1999, there were three super-aggregations (∼55x75 km across), which were stable for over a month. During both 1998 and 1999, sperm whales were uniformly distributed with respect to mean depth, slope and sea surface temperature over spatial scales of ∼10, 19, and 37 km segments and over areas of ∼70x90 km. There was no close association between sperm whale distribution and the distribution of jumbo squid landings in 1998. In 1999, about two-thirds of the individuals were found in areas of possibly high jumbo squid biomass. There was a significant correlation between the occurrence of sperm whales and that of bottlenose dolphins (Tursiops truncatus), despite the fact that they usually inhabit different water depths. This is the first study which was able to relate sperm whale distribution and relative abundance to the abundance of their main prey items. It suggests that sperm whales change their distribution in response to a decline in jumbo squid but that they do not leave the Gulf of California. However, this study encompassed only 2 years and further investigations are needed to gain an understanding of what may trigger large-scale movements.
AB - Sperm whales (Physeter macrocephalus) feed predominantly on meso- and bathypelagic cephalopods for which effective sampling methods have not been developed. The Gulf of California is one of the very few areas where sperm whales might feed on a commercially fished species of squid (jumbo squid, Dosidicus gigas), presenting a unique opportunity to investigate the impacts of variations in jumbo squid abundance on sperm whale distribution. This study examines sperm whale distribution and relative abundance in relation to the distribution of D. gigas, other cetacean species and key environmental features over spatial scales ranging from a few kilometers to a several hundreds of kilometers. Data were collected during two field seasons in spring-summer 1998 and 1999 using non-invasive techniques. Landing statistics show that the jumbo squid fishery collapsed in 1998 and started recovering in early 1999. Despite this collapse in 1998, sperm whales remained abundant during both years, but there were strong differences in their aggregative behavior. In 1998, sperm whales were roughly evenly distributed, while in 1999, there were three super-aggregations (∼55x75 km across), which were stable for over a month. During both 1998 and 1999, sperm whales were uniformly distributed with respect to mean depth, slope and sea surface temperature over spatial scales of ∼10, 19, and 37 km segments and over areas of ∼70x90 km. There was no close association between sperm whale distribution and the distribution of jumbo squid landings in 1998. In 1999, about two-thirds of the individuals were found in areas of possibly high jumbo squid biomass. There was a significant correlation between the occurrence of sperm whales and that of bottlenose dolphins (Tursiops truncatus), despite the fact that they usually inhabit different water depths. This is the first study which was able to relate sperm whale distribution and relative abundance to the abundance of their main prey items. It suggests that sperm whales change their distribution in response to a decline in jumbo squid but that they do not leave the Gulf of California. However, this study encompassed only 2 years and further investigations are needed to gain an understanding of what may trigger large-scale movements.
UR - http://www.scopus.com/inward/record.url?scp=0036933775&partnerID=8YFLogxK
U2 - 10.1007/s00227-002-0839-0
DO - 10.1007/s00227-002-0839-0
M3 - Artículo
SN - 0025-3162
VL - 141
SP - 591
EP - 601
JO - Marine Biology
JF - Marine Biology
IS - 3
ER -