Abstract. We identify changes in the pelagic fish community of the tropical Pacific Ocean by comparing recent data collected by observers on longline fishing vessels with data from a 1950s scientific survey when industrial fishing commenced. A major shift in size composition and indices of species abundance and community biomass accompanied the start of fishing. The largest and most abundant predators, such as sharks and large tunas, suffered the greatest declines in abundance (21% on average). They also showed striking reductions in mean body mass. For example, the mean mass of blue shark (Prionace glauca) was 52 kg in the 1950s compared to 22 kg in the 1990s. The estimated abundance of this species was 13% of that in the 1950s. Overall, the biomass of large predators fell by a factor of 10 between the periods. By contrast, several small and formerly rare species increased in abundance, e.g., pelagic stingray (Dasyatis violacea). However, the increases in small species did not balance the reductions in the biomass of large predators. Of three possible explanations (fishing, environmental variation, and sampling bias), available evidence indicates fishing to be the most likely cause for the observed patterns.

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Abstract:We introduce a new method that uses generalized linear mixed models to infer the depth distribution of pelagic fishes. It uses existing data from research surveys and observers on commercial vessels to estimate changes in catchability when longline fishing gear is lengthened to access deeper water. We infer the depth distribution of catchability for 37 fish species that are caught on pelagic longlines in the Pacific Ocean. We show how the estimates of catchability can be used to correct abundance indices for variations in longline depth. Our method facilitates the inclusion of data from early surveys in the time series of commercial catch rates used to estimate abundance. It also resolves inconsistencies in the time series caused by a rapid switch to deep longlining in the 1970s. The catchability distribution does not always match depth preferences derived from tracking studies. Therefore, depth preferences from tracking studies should not be used to correct abundance indices without additional information on feeding behavior.Résumé : Nous présentons une nouvelle méthode qui utilise des modèles linéaires généralisés mixtes pour estimer la répartition des poissons pélagiques en fonction de la profondeur. La méthode exploite les données existantes d'inventaires scientifiques et d'observations faites sur les navires commerciaux afin d'estimer les changements de capturabilité qui se produisent lorsqu'on allonge les palangres pour pêcher en eau plus profonde. Nous estimons la répartition de la capturabilité en fonction de la profondeur chez 37 espèces de poissons récoltés à la palangre pélagique dans le Pacifique. Nous démontrons comment les estimations de capturabilité peuvent servir à corriger les indices d'abondance en fonction des variations de la profondeur des palangres. Notre méthode facilite l'inclusion de données d'inventaires plus anciens dans la série chronologique de taux de capture commerciaux utilisée pour estimer l'abondance. Elle permet aussi de résoudre les irrégularités dans la série chronologique causées par un passage rapide à la pêche à la palangre en profondeur durant les années 1970. La répartition de la capturabilité ne correspond pas toujours aux préférences de profondeur déterminées par les études qui traquent les poissons; il ne faut donc pas utiliser les préférences de profondeurs obtenues de ces études pour corriger les indices d'abondance s'il n'existe pas de renseignements supplémentaires sur le comportement alimentaire.[Traduit par la Rédaction] Ward and Myers 1142

The purpose of this investigation was to quantitatively and qualitatively identify the study methods and learning strategies that veterinary students used to study anatomy during their first year of professional school and to correlate these with their academic achievement and long-term recall of information. It was surmised that active study methods would be more beneficial than passive method, but this hypothesis was not supported. The activity or passivity of each study method was secondary to the way in which the students processed the learning. No single study method was associated with academic success or long-term recall; instead, successful students used a multitude of study methods while the struggling students relied on a single method alone, although these methods varied from student to student. Students and their study methods were profiled using the qualitative technique known as phenomenographic analysis to find those who studied in a deep or surface way. The deep-processing students, who commonly used multiple study methods, not only succeeded in the class but also had better recall. Students who relied on a memorization-heavy surface approach to learning had limited recall and tended to perform poorly in the class. These results strongly suggest that by encouraging students to integrate their studying by using multiple methods educators can improve both student grades and recall of complex topics.