Estimates of Red Drum Mortality via Acoustic Telemetry

Abstract

Subadult (age < 3) Red Drum Sciaenops ocellatus support a valuable recreational fishery, and mortality estimates for young Red Drum are needed for proper management. To obtain these estimates, age‐1 and age‐2 Red Drum were implanted with acoustic transmitters and external Floy tags in two coastal Alabama rivers (Fowl and Dog rivers). Fates of tagged fish were inferred from stationary receiver detections and active relocations over 1 year. These fates were used in a Bayesian multistate model to estimate instantaneous monthly and annual mortality and emigration rates for each river and overall from both rivers. Instantaneous monthly fishing mortality (F) ranged from 0.001 to 0.112 (annual F = 0.414) in Dog River, from 0.001 to 0.126 in Fowl River (annual F = 0.309), and was 0.001–0.054 (annual F = 0.337) overall. Instantaneous monthly natural mortality (M) ranged from 0.001 to 0.002 (annual M = 0.069) in Dog River, from 0.001 to 0.036 (annual M = 0.178) in Fowl River, and from 0.001 to 0.017 (annual M = 0.090) overall. The overall annual estimate of instantaneous total mortality (Z) was 0.435. The median escapement percentage was estimated at 36.3% (95% posterior credible interval = 19.5–56.0%) using M and Z from the overall model. Unfortunately, the error on this estimate was large and inconclusive as to whether the 30% escapement goal for juvenile Red Drum to the adult population from Dog and Fowl rivers is being met. Monthly residency estimates were typically greater than 0.90, and overall annual residency was estimated at 0.716. Fishing mortality estimates from the current study are higher than recent catch curve estimates that did not include young Red Drum. These results demonstrate that young Red Drum need to be accounted for when generating mortality estimates and provide needed data for the Red Drum recreational fishery.

Patterns and consequences of life history diversity in salinity exposure of an estuarine dependent fish

“…The metabolic costs of inhabiting salinities below their isosmotic equilibrium (Boeuf and Payan 2001), which is near 10 salinity (Crocker et al 1983;Forsberg and Neill 1997;Neill et al 2004), likely led to this slower growth rate; a common trend among euryhaline species (Lankford and Targett 1994;Secor et al 2000;Sampaio and Bianchini 2002). The largest consequence of slower growth during this life stage is that oligohaline resident Red Drum may remain in the harvestable slot limit for a longer duration, potentially increasing vulnerability to recreational harvest and oligohaline mortality rates (Nelson and Powers 2020b).…”

“…To rebuild populations, Red Drum harvest was banned in federal waters in 1988 (Gulf of Mexico Fishery Management Council 1988;Porch 2000;Hightower et al 2016). Since commercial harvest cessation, a valuable recreational fishery has developed that primarily targets juvenile fish (1-4 years old) in inshore waters (Porch 2000;Nelson and Powers 2020b). This fishery is tightly regulated to ensure that 30% of juveniles escape the inshore fishery and contribute to the adult spawning stock (Powers and Burns 2010;Powers et al 2012).…”

Environmental Drivers of Vibrio cholerae Abundances in Mobile Bay, Alabama

“…4 ). The northernmost site (DR) is located at the mouth of Dog River, a 13-km-long, tidally influenced shallow river ( 39 ). The Fowl River (FR) site is located near Fowl River, a 23.2-km-long, brackish river originating near Theodore, AL ( 39 ).…”

“…The northernmost site (DR) is located at the mouth of Dog River, a 13-km-long, tidally influenced shallow river ( 39 ). The Fowl River (FR) site is located near Fowl River, a 23.2-km-long, brackish river originating near Theodore, AL ( 39 ). The Cedar Point (CP) site is in the Mississippi Sound, north of Dauphin Island, a barrier island located 3 mi south of the mouth of Mobile Bay in the Gulf of Mexico.…”

Toward a decade of ocean science for sustainable development through acoustic animal tracking

“…(a) The pearly razorfish, Xyrichtys novacula: an array of acoustic receivers has revealed that movement variability plays a key role when estimating true abundance from catches (Alós et al, 2019). (b) The red drum, Sciaenops ocellatus: AT have been used to estimate its instantaneous monthly and annual fishing mortality, a key parameter for fisheries management, in two coastal Alabama rivers (Nelson & Powers, 2020). (c) The common dentex, Dentex dentex: a combination of AT and data-driven modelling approaches provided a tool to identify aggregation areas that make this species highly vulnerable to fishing (Aspillaga et al, 2017).…”