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Movement patterns of some coral reef fishes change with natural cycles (e.g., tidal, lunar and seasonal), resulting in short-term shifts in fish assemblages. We reviewed the literature on temporal changes in coral reef fish assemblages derived from underwater visual census (UVC) and found that movement was rarely considered in experimental design and analysis or as cause of change in interpretation of the results. Studies of vagile species, large individuals, species forming transient spawning aggregations and studies of fishes in contiguous habitats are most likely to be affected by such movements. Ignoring predictable patterns of movement associated with such natural cycles in survey design and analysis increases “unexplained” variation, making it more difficult to detect longer-term changes in fish assemblages and reducing the effectiveness of UVC as a monitoring tool. [ABSTRACT FROM AUTHOR]

Understanding the movement behaviour of any species is important for developing species-specific management and conservation measures. In recent years, the sicklefin lemon shark Negaprion acutidens has shown rapid range reductions and has even disappeared altogether in certain areas. In this study, the area use patterns and site fidelity of the N. acutidens were assessed at the St. Joseph Atoll in the Seychelles. Passive acoustic telemetry methods were employed to monitor the movements of 19 tagged individuals for 1 year. Area use within the lagoon of the atoll was found to be highly restricted, with individuals typically utilising a small portion of the available area throughout the year. A high-use zone was apparent in the south-east of the atoll's lagoon, which was shared by many of the monitored individuals. Fidelity to the study site was found to be extremely high, with the 79 % of tagged N. acutidens still present in the atoll at the end of the study. Individuals displayed both diel and tidal movements between the lagoon and surrounding habitats. The restricted area use and high site fidelity observed in this study highlight both the vulnerability of this species to rapid over exploitation and importance of remote habitats such as the St. Joseph Atoll in their future conservation. The results obtained here can be used to inform management decisions regarding the development and utilisation of similar atoll environments throughout the species' range. [ABSTRACT FROM AUTHOR]

Provides information on a study which examined the horizontal and vertical movements of large bigeye tuna, Thunnus obesus, captured in the south Pacific Ocean. Materials and methods; Observations on the vertical movements of the fish and the oceanographic conditions at the time of the movements; Results and discussion.

Estimating the abundance of pelagic fish species is a challenging task, due to their vast and remote habitat. Despite the development of satellite, archival and acoustic tagging techniques that allow the tracking of marine animals in their natural environments, these technologies have so far been underutilized in developing abundance estimations. We developed a new method for estimating the abundance of tropical tuna that employs these technologies and exploits the aggregative behavior of tuna around floating objects (FADs). We provided estimates of abundance indices based on a simulated set of tagged fish and studied the sensitivity of our method to different association dynamics, FAD numbers, population sizes and heterogeneities of the FAD-array. Taking the case study of yellowfin tuna (Thunnus albacares) acoustically-tagged in Hawaii, we implemented our approach on field data and derived for the first time the ratio between the associated and the total population. With more extensive and long-term monitoring of FAD-associated tunas and good estimates of the numbers of fish at FADs, our method could provide fisheries-independent estimates of populations of tropical tuna. The same approach can be applied to obtain population assessments for any marine and terrestrial species that display associative behavior and from which behavioral data have been acquired using acoustic, archival or satellite tags. [ABSTRACT FROM AUTHOR]