ABSTRACT. Fishing cooperatives (co-ops) and patron-client relationships are the most common cooperative and noncooperative strategies for self-governance for small-scale fisheries around the world. We studied what drives fishers to choose between these two self-governance arrangements in 12 communities in the Gulf of California, Mexico. The communities depend on similar fishing resources, are located in contiguous portions of the coast, fish roughly the same species, have similar socioeconomic characteristics, and sell to similar markets, yet half of the fisheries are organized around co-ops and the other half work through patron-client arrangements. Using participant observation, in-depth interviews of key informants between 1995-2008, and a survey of 55% of the fisheries in the study area, we found that the presence of high transaction costs of commercialization, the desire to acquire fishing licenses, and the existence of traditions of successful collective action among fishing groups within each community strongly influence fishers' choices regarding membership in fishing co-ops. We also examined the implications of our findings for conservation of fishing resources. Given that the emergence of co-ops was associated with high transaction costs of commercialization, we hypothesize that cooperative strategies are more likely than patron-client strategies to emerge in communities in isolated locations. In an era of globalization, in which the rate of development and urbanization will increase in coastal areas, patron-client strategies are likely to become more prevalent among fisheries, but such self-governance strategies are thought to be less conducive to conservation behaviors.RESUMEN. Las cooperativas pesqueras y los arreglos informales directos entre el pescador y el comprador son las estrategias de cooperación y no cooperación más comunes de la autogobernanza de la pesca artesanal a escala global. Investigamos cuáles son los factores que influyen en la elección de los pescadores entre una y la otra, en doce comunidades del Golfo de California, México. Todas las comunidades del área de estudio son semejantes ya que dependen de los mismos recursos pesqueros, se ubican en una zona costera contigua, por lo general capturan las mismas especies, presentan características socioeconómicas similares y comercializan en mercados equivalentes. Sin embargo, casi la mitad de los pescadores se ha organizado en cooperativas y la otra mitad de manera individual en arreglos informales directos con los compradores. Para entender el contexto de la localidad, entre 1995 y 2008 utilizamos técnicas de observación participativa y entrevistas a fondo con informantes clave, así como una encuesta aplicada al 55% de los pescadores del área de estudio. Descubrimos que la existencia de altos costos de transacción para la comercialización del producto, el deseo de obtener permisos de pesca artesanal comercial y las tradiciones de acción colectiva de los diferentes grupos pesqueros en cada comunidad, influye sobremanera en la estrategia...