Understanding and Managing Living Resources

Southern Flounder, Paralichthys lethostigma, is an economically important fish in the northern Gulf of Mexico. Recent stock assessments throughout the species' range indicate that stocks are overfished or experiencing overfishing. In the absence of a recent Mississippi Southern Flounder stock assessment, an examination of its management strategy is necessary. Here, we develop per-recruit models using life history characteristics of Southern Flounder caught in Mississippi waters. To account for the species' annual spawning migration, we use acoustic telemetry tagging data to inform on the total proportion of individuals that migrate and times of egress from nearshore habitats to offshore spawning locations. We observed differences in yield- and spawning-stock-biomass-per-recruit when accounting for Southern Flounder movement dynamics and the lack of an offshore fishery compared to traditional per-recruit models. Results indicate that changes to current management strategies could benefit the Southern Flounder stock. Our study provides a framework for decision-makers regarding a declining stock.

Mangrove Snapper (Lutjanus griseus) in the northern Gulf of Mexico are considered data limited by state and federal management agencies. Life history and movement data are needed for this species as they are increasingly in demand from both the recreational and commercial sector given restrictions on other reef fish species. Mangrove Snapper are a euryhaline species that use brackish estuaries as a nursery habitat before undergoing an ontogenetic shift to offshore habitat. Prior to this shift, they are generally thought to be a sedentary species and closely associated with structured (e.g., reef, rubble, mangrove) habitats. Our goal is to use acoustic telemetry in conjunction with age and growth data to fill knowledge gaps about when they transition from inshore to offshore habitats, where they overwinter, generate estimates of inshore movements, and determine how salinity changes impact habitat selection and spatial dynamics. A total of 19 and 10 juvenile Mangrove Snapper have been implanted with Innovasea V9 acoustic transmitters in the Pascagoula River and Bayou Cassotte Industrial Channel, Mississippi, respectively. Initial telemetry analysis suggests that Mangrove Snapper show high site fidelity with limited movement between structured habitats. Currently 128 individuals have been sampled (71 males, 56 females, 1 unknown) from the Pascagoula River for the age and growth study. Individuals were weighed and measured, sexed, had gonads weighed, and the sagittal otoliths were collected. Monthly mean Gonadosomatic index was calculated to determine if potential nearshore spawning could be occurring. Growth will be modeled and compared to other systems. Age data will be used to inform age of offshore movement and to determine the age of sexual maturity.

Blacktip Sharks, Carcharhinus limbatus, are targeted in recreational and commercial fisheries across the U.S. Gulf of Mexico (GoM). Recent studies have supported biological separation between the eastern and western GoM for Blacktip Sharks, yet comprehensive reproductive information from both areas is lacking. Reproductive data from 1,308 Blacktip Sharks were examined from the eastern and western GoM. Median size- and age-at-maturity differed significantly by sex and region. Median length-at-maturity was 94.7 and 100.6 cm FL for males and females in the western GoM and 105.7 and 116.1 cm FL for males and females in the eastern GoM. Median age-at-maturity was 3.1 and 3.5 years for males and females in the western GoM and 4.7 and 6.4 years for males and females in the eastern GoM. These results demonstrate differences in Blacktip Shark life history between the eastern and western GoM and indicate that separate quotas are appropriate for effective fisheries management.

Depredation (the partial or complete removal of a hooked species by a non-target species) is a human-wildlife conflict as old as fishing itself. In some ways, depredation is no different today than it was a century ago. But in many ways, this conflict has become more complicated. Following three decades of successful management, some US shark populations have begun to rebuild. However, many anglers attribute perceived increases in shark depredation to management measures, claiming they have led to an "overpopulation" of sharks and/or learned behavior by sharks. We investigated whether these factors could explain the reported increases in depredation. Based on fishery-independent surveys, neither shark population increases nor learned behavior by sharks is evident. However, increases in angler effort provide an alternative explanation that is not often considered. While far from a smoking gun, at least four themes emerge from this thought exercise. First, it is important to understand historical predator baselines. Second, it is important to acknowledge lifting baselines, i.e., instances where previously depleted populations are recovering. Third, it is important to remember that there are many instances when stakeholder observations were initially misaligned with traditional scientific observations but were ultimately recognized as pivotal for filling data gaps. Finally, and perhaps most important, is the acknowledgement that perceived conflict is as potent as real conflict. Arguably, it may not matter if depredation has increased or decreased; the overwhelming perception from stakeholders is an increase in depredation, and this is the perceived (or real) conflict that must be addressed.