Movements and space use of giant trevally in coral reef habitats and the importance of environmental drivers

Background: Effective conservation of large predators requires a broad understanding of their ecology. Caranx ignobilis is a large marine predator well represented in coral reef environments, yet they are poorly studied. Passive acoustic monitoring was used to track the movements of 20 C. ignobilis at offshore reefs in the central Great Barrier Reef from 2012 to 2014. Using a modelling approach, temporal changes in movement patterns of C. ignobilis were explored to determine if individuals exhibited predictable movement patterns. The effects of biological and environmental variables on monthly space use, daily presence and hourly depth use were investigated to define any response to environmental changes. Results: Caranx ignobilis typically remained at their capture reef with 98.8% of detections recorded at these locations. Individuals were recorded in the study site for periods from 9 to 335 days (mean = 125.9) with a mean residency index of 0.53, indicating movements away from the reef or out of detection range occurred on the scale of days. Inter-reef movements from only three individuals were recorded which coincided with the summer full moon so may have been related to spawning behaviour. Environmental drivers were correlated with daily presence and hourly depth use of C. ignobilis but had little influence on monthly space use. There was little or no effect of fish size on space use, presence and depth use. Conclusion: By improving the current understanding of movement patterns of this large teleost among individual coral reefs, the results of this study reveal that site attachment may be present and that environmental parameters play a role in observed movement patterns related to depth and presence. These data provide useful information for the development of management plans, particularly in relation to space-based protection

Continental-scale animal tracking reveals functional movement classes across marine taxa

Acoustic telemetry is a principle tool for observing aquatic animals, but coverage over large spatial scales remains a challenge. To resolve this, Australia has implemented the Integrated Marine Observing System's Animal Tracking Facility which comprises a continental-scale hydrophone array and coordinated data repository. This national acoustic network connects localized projects, enabling simultaneous monitoring of multiple species over scales ranging from 100 s of meters to 1000 s of kilometers. There is a need to evaluate the utility of this national network in monitoring animal movement ecology, and to identify the spatial scales that the network effectively operates over. Cluster analyses assessed movements and residency of 2181 individuals from 92 species, and identified four functional movement classes apparent only through aggregating data across the entire national network. These functional movement classes described movement metrics of individuals rather than species, and highlighted the plasticity of movement patterns across and within populations and species. Network analyses assessed the utility and redundancy of each component of the national network, revealing multiple spatial scales of connectivity influenced by the geographic positioning of acoustic receivers. We demonstrate the significance of this nationally coordinated network of receivers to better reveal intra-specific differences in movement profiles and discuss implications for effective management

A comparison between traditional kernel-based methods and network analysis: an example from two nearshore shark species

Understanding how marine species use their environment has become increasingly important in management and conservation. Acoustic monitoring allows long-term tracking of marine animal movement that is traditionally analysed using kernel-based home range estimators. These traditional methods, however, are limited because they do not examine movement pathways within activity spaces. Network analysis (NA) provides an alternative approach to traditional home range analysis that treats acoustic receivers as network nodes and analyses movement between nodes. To investigate the utility of NA in identifying core use areas and compare the results with traditional analysis, a case study using acoustically monitored coastal sharks was conducted. To make direct comparisons with static traditional analysis a temporal scale was not explicitly explored. Comparison of traditional analysis and NA demonstrated that both methods provided similar results for identifying core use areas (50% kernel utilization distribution (KUD) equivalent), but that NA tended to overestimate general use areas (95% KUD equivalent) compared to kernel-based methods. Furthermore, frequent bidirectional movements within core use areas were identified by NA, indicating the importance of movement corridors within or between core areas. Movements between acoustic receivers outside core use areas were less frequent and unidirectional suggesting transiting movements. Therefore, NA may be a practical alternative to traditional home range metrics by providing useful data interpretation that allows for a comprehensive picture of animal movement, including identifying core use areas and pathways used

Spatial substitution strategies of recreational fishers in response to zoning changes in the Great Barrier Reef Marine Park

Understanding fishers' responses to marine spatial closures is important for both resource users and managers. Fishing is a major recreational activity in Australia, and recreational fishers are key local resource users within the Great Barrier Reef Marine Park. In 2004, implementation of a new zoning plan in the park resulted in a reduction in the amount of area available to recreational fishing. A combination of phone, mail, and face-to-face surveys was used to investigate recreational fishers' choices and spatial redistribution strategies in response to the reduction in fishing area. Approximately 56% of fishers reported losing at least one of their regular fishing locations under the new zoning plan. Fishers generally compensated by shifting their fishing effort to other areas they knew to be good fishing locations, and by finding new areas that they had not exploited previously. Potential implications of these spatial changes in recreational fishing effort for both the marine park and recreational fishers include changes in fishing frequency and satisfaction, reduced fishing quality, restricted access to areas considered to be of high quality for recreational fishing, increased crowding in areas that remain open to fishing, and increased likelihood of localized depletions in popular recreational fishing locations. Identification of the drivers of the spatial distribution of fishing effort, factors affecting fishers' choices of locations, and adaptation strategies adopted by fishers provide a valuable tool to help understand the impact of spatial fishing closures on fishers and resources

Author Correction: Global status and conservation potential of reef sharks

An Amendment to this paper has been published and can be accessed via a link at the top of the paper.</p