Disentangling the response of fishes to recreational fishing over 30 years within a fringing coral reef reserve network

Few studies assess the effects of recreational fishing in isolation from commercial fishing. We used meta-analysis to synthesise 4444 samples from 30 years (1987–2017) of fish surveys inside and outside a large network of highly protected reserves in the Ningaloo Marine Park, Western Australia, where the major fishing activity is recreational. Data were collected by different agencies, using varied survey designs and sampling methods. We contrasted the relative abundance and biomass of target and non-target fish groups between fished and reserve locations. We considered the influence of, and possible interactions between, seven additional variables: age and size of reserve, one of two reserve network configurations, reef habitat type, recreational fishing activity, shore-based fishing regulations and survey method. Taxa responded differently: the abundance and biomass inside reserves relative to outside was higher for targeted lethrinids, while other targeted (and non-targeted) fish groups were indistinguishable. Reef habitat was important for explaining lethrinid response to protection, and this factor interacted with reserve size, such that larger reserves were demonstrably more effective in the back reef and lagoon habitats. There was little evidence of changes in relative abundance and biomass of fishes with reserve age, or after rezoning and expansion of the reserve network. Our study demonstrates the complexities in quantifying fishing effects, highlighting some of the key factors and interactions that likely underlie the varied results in reserve assessments that should be considered in future reserve design and assessment

Whole mitogenome sequencing refines population structure of the Critically Endangered sawfish Pristis pristis

The largetooth sawfish Pristis pristis (Linnaeus, 1758) is a highly threatened euryhaline elasmobranch that in recent times has undergone a significant range contraction. It now only remains in a few areas, with northern Australia being the main stronghold. Previous work using a single mitochondrial gene approach suggested the existence of regional barriers to gene flow in northern Australia. In this study, whole mitochondrial sequences of 92 P. pristis from 7 river drainages across northern Australia were used to refine the population structure. This approach revealed barriers to gene flow at a scale as fine as between adjacent river drainages. Except for those flowing into the Gulf of Carpentaria, all river drainages appeared to host a genetically distinct population. The apparent genetic homogeneity in the Gulf is probably due to freshwater connectivity between river drainages, either during the last glaciation event when the Gulf was a freshwater lake or through contemporary wet season flooding. These results suggest that each river drainage across the species' range should be considered a discrete management unit unless there is evidence of freshwater connectivity. More broadly, the improved resolution of population structure obtained with whole mitogenome analysis compared to single mitochondrial gene approaches suggests that female reproductive philopatry may have been overlooked in previous studies of some elasmobranch species

Seasonal use of a macrotidal estuary by the endangered dwarf sawfish, Pristis clavata

Sawfishes (Family: Pristidae) are one of the most imperilled fish families worldwide. There is an increasingly urgent need to better understand the biology, ecology, and population status of the five sawfish species to develop more effective conservation measures. The dwarf sawfish, Pristis clavata, is one of the least researched members of the pristids, with literature limited to analysing disparate datasets or collations of rare encounters in northern Australia. This study examined the spatial ecology of dwarf sawfish using targeted surveys and acoustic telemetry to determine its habitat use in a macrotidal estuary in northern Australia. Seventeen dwarf sawfish were tagged with acoustic transmitters and monitored in the Fitzroy River estuary and adjacent King Sound (Kimberley, Western Australia) between August 2015 and November 2017. Dwarf sawfish observed within the Fitzroy River estuary and King Sound were juveniles, ranging between 740 and 2,540 mm in total length. Catch per unit effort of dwarf sawfish in the late dry season was relatively high in the estuary, with the catch rate in 2015 being one of the highest reported for any sawfish species. Acoustic detections revealed a distinct seasonal pattern in the use of different parts of the estuary and King Sound, which was found to be driven by salinity. Dwarf sawfish predominately occupied a single large pool near the terminus of the tidal limit in the late dry season (August–November), before transitioning to regions in closer proximity to the river mouth or in King Sound in the wet and early dry seasons (December–July). Given the high abundance and residency of dwarf sawfish in the Fitzroy River estuary, this area is an important nursery for the species during the late dry season and should be formally recognized as a habitat protection area for the species

One panel to rule them all: DArTcap genotyping for population structure, historical demography, and kinship analyses, and its application to a threatened shark

With recent advances in sequencing technology, genomic data are changing how important conservation management decisions are made. Applications such as Close‐Kin Mark‐Recapture demand large amounts of data to estimate population size and structure, and their full potential can only be realised through ongoing improvements in genotyping strategies. Here we introduce DArTcap, a cost‐efficient method that combines DArTseq and sequence capture, and illustrate its use in a high resolution population analysis of Glyphis garricki , a rare, poorly known and threatened euryhaline shark. Clustering analyses and spatial distribution of kin pairs from four different regions across northern Australia and one in Papua New Guinea, representing its entire known range, revealed that each region hosts at least one distinct population. Further structuring is likely within Van Diemen Gulf, the region that included the most rivers sampled, suggesting additional population structuring would be found if other rivers were sampled. Coalescent analyses and spatially explicit modelling suggest that G. garricki experienced a recent range expansion during the opening of the Gulf of Carpentaria following the conclusion of the Last Glacial Maximum. The low migration rates between neighbouring populations of a species that is found only in restricted coastal and riverine habitats show the importance of managing each population separately, including careful monitoring of local and remote anthropogenic activities that may affect their environments. Overall we demonstrated how a carefully chosen SNP panel combined with DArTcap can provide highly accurate kinship inference and also support population structure and historical demography analyses, therefore maximising cost‐effectiveness