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Precipitous declines in pinto abalone (Haliotis kamtschatkana kamtschatkana) abundance in the San Juan Archipelago, Washington, USA, despite statewide fishery closure

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Pinto abalone (Haliotis kamtschatkana kamtschatkana) index stations in the San Juan Archipelago were systematically monitored by the Washington Department of Fish and Wildlife from 1992 through 2006. During this period, abalone abundance declined by 77% and the mean shell length (SL) increased 10.4mm. Abalone densities at all index stations are currently well below the threshold of 0.15 abalone·m–2 required for successful fertilization. From 1992 to 1996, 16% of individuals encountered measured<90mm SL, while only 6% of the individuals from 2003 to 2006 were in this small size class. Similarly, the number of those>114mm SL was greater in the 2000s than in the 1990s. The mean SL of all live abalone observed in the 1990s (107.62± 0.87mm) was significantly different from the mean SL of empty shells (114.21± 2.1mm), but no difference was detected between the mean SLs of empty shells and live abalone in the 2000s (114.97± 1.42mm). Taken together, these data suggest recruitment failure from an Allee response to low population densities.

Le ministère de la pêche et de la faune de l’état de Washington (Washington Department of Fish and Wildlife) a suivi systématiquement les stations de référence de l’ormeau nordique (Haliothis kamtschatkana kamtschatkana) dans l’archipel de San Juan de 1992 à la fin de 2006. Durant cette période, l’abondance des ormeaux a diminué de 77% et la longueur moyenne des coquilles (SL) a augmenté de 10,4 mm. Les densités des ormeaux à toutes les stations de référence sont actuellement bien en deçà du seuil de 0,15 ormeau·m–2 requis pour une fécondation réussie. En 1992–1996, 16% des individus observés avaient une SL< 90 mm, alors qu’en 2003–2006 seuls 6% des individus appartenaient à cette classe de petite taille. De même, le nombre d’individus avec une SL> 114 mm était plus important durant les années 2000 que durant les années 1990. La longueur moyenne des coquilles de tous les ormeaux vivants observés durant les années 1990 (107,62 ± 0,87 mm) est significativement différente de la longueur moyenne des coquilles vides (114,21 ± 2,1 mm), mais il n’y a pas de différence détectable entre les longueurs moyennes entre les coquilles vides et celles des ormeaux vivants durant les années 2000 (114,97 ± 1,42 mm). Dans leur ensemble, ces données laissent croire à un échec du recrutement dû à une réaction de type Allee aux faibles densités de population.

Document Type: Research Article

Publication date: December 1, 2008

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  • Published continuously since 1901 (under various titles), this monthly journal is the primary publishing vehicle for the multidisciplinary field of aquatic sciences. It publishes perspectives (syntheses, critiques, and re-evaluations), discussions (comments and replies), articles, and rapid communications, relating to current research on cells, organisms, populations, ecosystems, or processes that affect aquatic systems. The journal seeks to amplify, modify, question, or redirect accumulated knowledge in the field of fisheries and aquatic science. Occasional supplements are dedicated to single topics or to proceedings of international symposia.
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