[MARMAM] Papers on bottlenose dolphins from Mexican waters

Eduardo Morteo eduardo.morteo at gmail.com
Tue Sep 13 20:59:18 PDT 2011


Below you will find two papers on bottlenose dolphins from Mexican waters. Both can be downloaded from the web. For PDF copies please mail: emorteo at gmail.com.

PAPER 1:

Morteo, E., G. Heckel, R.H. Defran y Y. Schramm. 2004. Distribution, movements and group size of the bottlenose dolphin (Tursiops truncatus) to the south of San Quintín, Baja California, Mexico. Ciencias Marinas, 30(1A): 35–46.

ABSTRACT: Twelve boat-based photoidentification surveys were carried out along the coast south of San Quintin Bay, in Baja California, Mexico from July 1999 to June 2000; effort was 276.76 km and 31.7 h at sea. Twenty-two schools were encountered and 12.9 h of total observation were spent with 242 dolphins in these schools. School size averaged 11 (S.D.=8) dolphins, although it is possible that groups are actually smaller; nursing groups were significantly larger (p<0.05), with frequent membership exchanges occurring among schools. Dolphins preferred a coastal strip between 250 and 500 m offshore (p<0.05), at depths below 7 m, and with sandy substrates (p<0.05). Greater sighting frequencies occurred in two coastal zones (p<0.05) and feeding was common around the mouth of the bay. Dorsal fin photographs led to the identification of 169 dolphins, and 124 were different individuals. During the study period the coast south of San Quintin was a pass zone for transient dolphins, since most of these animals (>70%) were sighted one time or stayed for short periods. A total of 220 different dolphins have been identified in the San Quintin area when these data are combined with those gathered by Caldwell (1992) in 1990; these dolphins probably represent a small part of a larger population. More research on bottlenose dolphins’ population biology in this and adjacent geographic areas is needed to develop better conservation and management strategies for this important natural resource.

KEYWORDS: Distribution, movements, ecology, Tursiops truncatus, San Quintín.

PAPER 2:

Morteo E., A. Rocha-Olivares, P. Arceo-Briseño, y L.G. Abarca-Arenas. 2011. Spatial analyses of bottlenose dolphin-fisheries interactions reveal human avoidance off a productive lagoon in the western Gulf of Mexico. Journal of the Marine Biological Association of the United Kingdom. doi: 10.1017/S0025315411000488.

ABSTRACT: Studying interactions between cetaceans and humans is fundamental to assess their ecological significance and the impact of human activities on marine wildlife. Delphinids have historically been associated with human maritime activities, and while evidence suggests that such interactions are becoming more frequent worldwide, these remain poorly studied. Areas of potential interaction and differences in dolphin affinity to interact with humans were used to test hypotheses about the spatial distribution and temporal variation in dolphin-fisheries interactions off the highly productive Alvarado lagoon, in the western Gulf of Mexico. Line-transect surveys yielded 928 dolphin, 980 vessel, and 320 fishing gear target records, the latter involving mostly the shrimp fishery. No temporal differences were found in daily relative abundance of dolphins (average=8.1 h-1, sd=9.7), vessels (average=7.8 h-1, sd=5.9) or fishing gear (average=2.4 h-1, sd=2.6) between two consecutive years. Non-random spatial distributions indicated higher target concentrations at the lagoon entrance; however, dolphins and fishers were found to evade each other, possibly to prevent competition. Dolphins only interacted with gillnets (28.6% of vessels and 22.6% of fishing gear). We observed small areas of potentially intentional and random encounters outside the entrance of the lagoon and low or null potential for interactions elsewhere. Only 18.9% of dolphin schools (44.8% of the 172 photo-identified animals) interacted with fisheries mostly by chance. Resident individuals (n= 23) tended to avoid humans, likely in response to negative reinforcement caused by aggressions from fishers. Hence, the potential intentionality of a few individuals to interact with fisheries, show they bare higher risks while attempting to benefit from gillnetted prey. This research unveils the chronic and acute exposure of the dolphin community to artisanal fisheries within the area, having important reciprocal consequences on their distributions and activities.
KEYWORDS: Abundance, Distribution, Dolphin-fisheries interactions, Coastal bottlenose dolphins, Tursiops truncatus

Cheers!

Eduardo Morteo, PhD

Head Researcher
Marine Mammal Laboratory

Institute of Marine Sciences and Fisheries
Universidad Veracruzana

617 Calle Hidalgo, Col. Río Jamapa, Boca del Río, Veracruz, Mexico. CP 94290

Ph: +52 (229) 956 72 27 Ext. 114
Fax: +52 (229) 956 70 70

E-mail: emorteo at uv.mx

http://www.uv.mx/icmp
http://www.labmmar.net

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