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Background With the increase in telemetry studies over the past decade, improving understanding of how different tagging methods influence the probability of presence in a receiver array is important in maximizing the resulting data. Disappearance from the array may be due to mortality from surgery complications, tag loss, predation, or emigration. Internally tagging fish on a boat can cause barotrauma injuries, increased stress from prolonged handling times, or predation after fish have been released back into the water. Conducting in situ internal acoustic tagging at depth of capture removes barotrauma stresses and simplifies the release method, which may improve fish survival and decrease risk of disappearance from the array. In this study, we used 8 years of acoustic tagging data to determine if the tagging method (in situ versus on the boat) influenced the likelihood of a fish being detected 4 and 6 days after the tagging event. Results At 6 days after tagging, Kaplan–Meier survival curves revealed that the probability of presence for fish tagged on the boat was 66% compared to 90% for fish tagged in situ. Tagging method was the only variable to significantly affect probability of presence based on Cox proportional hazards models, with fish tagged in situ ~ 75% less likely to disappear from the array compared to fish tagged on the boat at both 4 and 6 days after tagging. Examining tagging methods separately, handling time only marginally influenced probability of presence of boat-tagged fish and no variables had a significant effect on probability of presence of in situ tagged fish. Conclusions In this study, tagging method was the only variable to significantly affect the probability of presence for internally tagged fish. Other factors had little to no influence, but correlation of variables limited what factors could be included in the models. Implanting internal acoustic tags in situ is not a practical method for every species and for every environment, but given the increased probability of presence demonstrated here, we strongly suggest it be considered where applicable.

Yellowtail snapper, Ocyurus chrysurus (Bloch, 1970), is an important fisheries species in the Florida Keys. In 2008–2009, yellowtail snapper were tagged with acoustic transmitters and tracked through an array of 86 stationary receivers in the Dry Tortugas' network of marine reserves in Florida to determine site fidelity, home range, and temporal patterns of habitat use. Fifteen yellowtail snapper were tracked for 1–427 d [x = 188 (SE 39)]. A multistep method for data validation ensured that only the fish with high-quality detection data were selected for data analyses. Brownian bridge models were used to estimate home range rather than more traditional methods because they incorporate not only detection location, but also time between detections, the path between successive detections, and location error. For a species typically described as transient, six of the tagged yellowtail snapper had high site fidelity [x = 58.4% (SE 8.4%)], and Brownian bridge models estimated relatively small minimum home ranges [x = 5.45 km2 (SE 1.79)]. Movements were highly variable, but analyses showed that fish displayed diel and seasonal trends, and in general, were more likely to be absent during summer months or during dusk and at night. Tagged yellowtail snapper showed a preference for reef edge habitat, swimming in and out of the marine reserve where the boundary intersected this type of habitat. The knowledge that yellowtail snapper is less transient than previously believed and understanding the habitat preference and temporal movements of this species can help with its future management.

The Mississippi coastal region has two major rivers and four smaller rivers influencing the estuaries that make up the Mississippi Sound. The islands off Mississippi create a barrier which allows the area to be a widespread, productive estuarine region. With such a dependence on discharge from the drainages, it is important to understand the effect of salinity regimes on fish communities. Drought conditions in other regions have been shown to dramatically change the fish community structure. We used the long running Interjurisdictional Fisheries Program database (2006–2014) within Mississippi state waters and compared yearly fish communities between drought and non-drought years. Non-metric Multidimensional Scaling (nMDS), Analysis of Similarity (ANOSIM), and Indicator Species Analysis (ISA) were used to compare drought and non-drought conditions in the Mississippi Sound. During 2006 and 2007, which were identified as drought years by the Palmer Drought Severity Index (PDSI), differences in fish community structure were identified and compared to non-drought years (2008–2009 and 2011–2014). The ISA identified a total of eight species that were significantly influenced by drought years. Of the eight species, the abundance of seven species significantly decreased while the abundance of one species significantly increased. With an increasing human population in central and south Mississippi, pressure on freshwater resources is likely to increase, resulting in possible changes in the fish community dynamics of the Mississippi Sound. Understanding the influence of decreased river discharges will assist managers in determining the impacts of freshwater withdrawals during base flow periods.