Interaction between the California sea lion and the artisanal fishery in La Paz Bay, Gulf of California, Mexico

Gamboa, David Aurioles; Rodríguez, F. Millán; Rodríguez, Mauricio Ramírez; Hernández‐Camacho, Claudia J.

doi:10.7773/cm.v29i3.151

Cited by 17 publications

(14 citation statements)

References 5 publications

(14 reference statements)

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“…The observations of the present study reflect the fact that the population dynamics at Los Islotes have remained the same over the last 20 years (Peterson and Bartholomew, 1967;Odell, 1975;Aurioles et al, 1983;Aurioles et al, 2003).…”

Section: Discussionsupporting

confidence: 50%

Natural and human disturbance in a rookery of the California sea lion (<i>Zalophus californianus californianus</i>) in the Gulf of California, Mexico

Labrada-Martagón¹,

Aurioles‐Gamboa²,

Martínez-Díaz³

2005

Lat. Am. J. Aquat. Mamm.

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Los Islotes is the southernmost breeding site of the California sea lion (Zalophus californianus californianus) in the Northern Hemisphere and represents one of the principal tourist attractions for the city of La Paz, Mexico. The tourism has been growing without control and could be the cause of perturbation in the reproductive and haul-out patterns of the sea lion. The aim of the present study was to determine the effect of tourism activities on the behavior of sea lions, in order to help design regulations to assure better use and conservation of the site. The nature and intensity of tourism activity and sea lion behavior were determined based upon monthly sampling over a one-year period (May 2000-April 2001. Tourist activity was higher during autumn and winter, with visits by "panga" boats being the most numerous. A total of 112 disturbances were recorded, the majority of which being non-anthropogenic causes. A quarter of disturbances were triggered by human activity within 20m of the rookery and with harassment reaction (animals going into the water) in 32% of the anthropogenic disturbances.Principal component analysis (PCA) described the conditions under which disturbance was generated (74% of the variation explained). Using three factors (47% of the total variation) the major contributing variables were month, tidal level, relative humidity, Beaufort number, total number of boats and number of powerboats and sailboats. In Los Islotes, the perturbation occurs mostly in autumn and winter coinciding with the highest frequency of tourism, large number of adult and subadult males and unfavorable environmental conditions for haul-out, such as high tide level and strong winds. The lowest number of disturbances occurred in summer, during the breeding season of the sea lion. Most of these, however, were caused by human activity. RESUMEN:Los Islotes es el sitio más sureño de reproducción del lobo marino de California (Zalophus californianus californianus) en el Hemisferio Norte y representa la principal atracción turística de la ciudad de La Paz, México. El turismo ha crecido sin ningún control y puede ser causa de perturbación de los patrones reproductivos y de descanso del lobo marino. El objetivo de este trabajo fue determinar el efecto de la actividad turística en el comportamiento del lobo marino con la finalidad de generar información útil para el diseño de acciones que garanticen un mejor aprovechamiento y conservación del sitio. Se caracterizó y cuantificó la actividad turística y se realizó un seguimiento del comportamiento con muestreos mensuales a lo largo de un año (Mayo 2000 -Abril 2001. La actividad turística fue mayor los meses de otoño e invierno, siendo la embarcación con motor tipo "panga" la más numerosa. Se registraron 112 disturbios, la mayoría de los cuales fueron generados por causas no antropogénicas. Un cuarto de los disturbios fueron ocasionados por causas humanas generándose a distancias menores de 20m de la lobera y ocasionando un efecto intenso (animales se van al agua) en el ...

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Section: Discussionsupporting

confidence: 50%

Natural and human disturbance in a rookery of the California sea lion (<i>Zalophus californianus californianus</i>) in the Gulf of California, Mexico

Labrada-Martagón¹,

Aurioles‐Gamboa²,

Martínez-Díaz³

2005

Lat. Am. J. Aquat. Mamm.

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“…The boats used in Mexico are generally much smaller, but the gear used and the length of time nets are left until retrieval are Julian & Beeson 1998;Aurioles-Gamboa et al 2003). In addition, in both California and Mexico, fishers and sea lions do not pursue the same species (Julian & Beeson 1998;Aurioles-Gamboa et al 2003). Sea lions are caught incidentally as they enter an area with nets.…”

Section: Estimating Mortality Ratesmentioning

confidence: 98%

“…Sea lions are caught incidentally as they enter an area with nets. Finally, the most important factor that determines bycatch rate in pinnipeds is the size of the net mesh opening (Zavala-Gonzalez & Mellink 1997;Julian & Beeson 1998;Aurioles-Gamboa et al 2003). Sea lions cannot enter nets with a small mesh size and can swim through nets with a large mesh size.…”

Section: Estimating Mortality Ratesmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 97%

“…The type of fishing that most commonly conflicts with California sea lions is the set gill-net fishery (Julian & Beeson 1998;Aurioles-Gamboa et al 2003). In fact, the threat of mortality due to incidental catch in gill nets is one of the gravest problems facing sea lions in this area (Zavala-Gonzalez & Mellink 1997;Programa de Manejo, Islas del Golfo de California 2000;Aurioles-Gamboa et al 2003). Although the direct impact of gill-net fishing on the sea lion population in the Gulf is unknown, incidental catch in gill and other fishing nets has contributed to population declines in northern fur seals (Callorhinus ursinus), harbor seals (Phoca vitulina stejnegeri), and harp seals (P. groenlandica) and is at least partially responsible for declines in Steller sea lions (Eumetopias jubatus) (Fowler 1987;Woodley & Lavigne 1991).…”

Section: Introductionmentioning

confidence: 99%

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Estimating Sustainable Bycatch Rates for California Sea Lion Populations in the Gulf of California

Underwood

Camacho

Aurioles‐Gamboa³

et al. 2008

Conservation Biology

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Commercial and subsistence fisheries pressure is increasing in the Gulf of California, Mexico. One consequence often associated with high levels of fishing pressure is an increase in bycatch of marine mammals and birds. Fisheries bycatch has contributed to declines in several pinniped species and may be affecting the California sea lion (Zalophus californianus) population in the Gulf of California. We used data on fisheries and sea lion entanglement in gill nets to estimate current fishing pressure and fishing rates under which viable sea lion populations could be sustained at 11 breeding sites in the Gulf of California. We used 3 models to estimate sustainable bycatch rates: a simple population-growth model, a demographic model, and an estimate of the potential biological removal. All models were based on life history and census data collected for sea lions in the Gulf of California. We estimated the current level of fishing pressure and the acceptable level of fishing required to maintain viable sea lion populations as the number of fishing days (1 fisher/boat setting and retrieving 1 day's worth of nets) per year. Estimates of current fishing pressure ranged from 101 (0-405) fishing days around the Los Machos breeding site to 1887 (842-3140) around the Los Islotes rookery. To maintain viable sea lion populations at each site, the current level of fishing permissible could be augmented at some sites and should be reduced at other sites. For example, the area around San Esteban could support up to 1428 (935-2337) additional fishing days, whereas fishing around Lobos should be reduced by at least 165 days (107-268). Our results provide conservation practitioners with site-specific guidelines for maintaining sustainable sea lion populations and provide a method to estimate fishing pressure and sustainable bycatch rates that could be used for other marine mammals and birds.

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An ecosystem modelling approach to deriving viable harvest strategies for multispecies management of the Northern Gulf of California

Lercari

Arreguı́n-Sánchez

2008

Aquatic Conservation

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ABSTRACT1. An ecosystem analysis was developed focusing on resource exploitation and biodiversity conservation for the Northern Gulf of California. The main tools employed were a trophic ecosystem model and time dynamic simulations.2. The ecosystem was represented by an Ecopath model that included 34 functional groups, from primary producers to top predators. It included relevant species in the area such as commercially important shrimp (e.g. Litopenaeus stylirostris) and highly endangered species (Phocoena sinus and Totoaba macdonaldi).3. Temporal simulations of changing fishing effort allowed the evaluation of fishing impact on the ecosystem components and, particularly, on protected species. Formal optimization methods were applied with the purpose of searching viable temporal patterns of fishing effort that might minimize social, economic and conservationist conflicts in the area.4. The results of those simulations showed the capability of the model to represent reference temporal series of relative biomass. The search for viable fishing strategies resulted in effort allocation consistent with those proposed by other studies; that is, a decrease in the industrial shrimp fleet (35-65%), a decrease in the gillnet fishing fleet (52-57%), and an increase of the artisanal shrimp fishery (63-222%).5. The main conflicts in the Northern Gulf of California seem to take place between social and conservation interests, while the economic and ecological benefits seem to be relatively independent. The next steps towards conflict resolution and ecosystem management should consider the design and operation of MPAs already established in the region.

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Interaction between the California sea lion and the artisanal fishery in La Paz Bay, Gulf of California, Mexico

Cited by 17 publications

References 5 publications

Natural and human disturbance in a rookery of the California sea lion (<i>Zalophus californianus californianus</i>) in the Gulf of California, Mexico

Natural and human disturbance in a rookery of the California sea lion (<i>Zalophus californianus californianus</i>) in the Gulf of California, Mexico

Estimating Sustainable Bycatch Rates for California Sea Lion Populations in the Gulf of California

An ecosystem modelling approach to deriving viable harvest strategies for multispecies management of the Northern Gulf of California

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