Seasonal variability in ichthyoplankton abundance and assemblage composition in the northern Gulf of Mexico off Alabama

Multiyear ichthyoplankton surveys used to monitor larval fish seasonality, abundance, and assemblage structure can provide early indicators of regional ecosystem changes. Numerous ichthyoplankton surveys have been conducted in the northern Gulf of Mexico, but few have had high levels of temporal resolution and sample replication. In this study, ichthyoplankton samples were collected monthly (October 2004–October 2006) at a single station off the coast of Alabama as part of a long-term biological survey. Four seasonal periods were identified from observed and historic water temperatures, including a relatively long (June–October) “summer” period (water temperature >26°C). Fish egg abundance, total larval abundance, and larval taxonomic diversity were significantly related to water temperature (but not salinity), with peaks in the spring, spring–summer, and summer periods, respectively. Larvae collected during the survey represented 58 different families, of which engraulids, sciaenids, carangids, and clupeids were the most prominent. The most abundant taxa collected were unidentified engraulids (50%), sand seatrout (Cynoscion arenarius, 7.5%), Atlantic bumper (Chloroscombrus chrysurus, 5.4%), Atlantic croaker (Micropogonias undulatus, 4.4%), Gulf menhaden (Brevoortia patronus, 3.8%), and unidentified gobiids (3.6%). Larval concentrations for dominant taxa were highly variable between years, but the timing of seasonal occurrence for these taxa was relatively consistent. Documented increases in sea surface temperature on the Alabama shelf may have various implications for larval fish dynamics, as indicated by the presence of tropical larval forms (e.g., fistularids, labrids, scarids, and acanthurids) in our ichthyoplankton collections and in recent juvenile surveys of Alabama and northern Gulf of Mexico seagrass habitats

Compression and Relaxation of Fishing Effort in Response to Changes in Length of Fishing Season for Red Snapper (Lutjanus campechanus) in the Northern Gulf of Mexico

A standard method used by fisheries managers to decrease catch and effort is to shorten the length of a fishery; however, data on recreational angler response to this simple approach are surprisingly lacking. We assessed the effect of variable season length on daily fishing effort, measured by using numbers of boat launches per day, anglers per boat, and anglers per day from video observations, in the recreational sector of the federal fishery for red snapper (Lutjanus campechanus) in coastal Alabama. From 2012 through 2017, season length fluctuated from 3 to 40 d. Daily effort, measured by using mean number of boat launches per day (coefficient of multiple determination [R2]=0.58) and mean number of anglers per day (R2=0.67), increased linearly with season shortening, indicating effort compression. In 2017, 2 seasons were allowed: an early season (3 d) and an unanticipated late season (39 d). Daily effort decreased during the late season, indicating that effort can also be relaxed if anglers anticipate longer seasons. Model fit for mean number of anglers per day improved with the addition of a daily wind factor (R2=0.94). The results of this study indicate that responses of anglers to changing fishing seasons are dynamic

Estimates of Red Drum Mortality via Acoustic Telemetry

Subadult (age \u3c 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

Age composition and distribution of red drum (Sciaenops ocellatus) in offshore waters of the north central Gulf of Mexico: an evaluation of a stock under a federal harvest moratorium

Because of a lack of fishery-dependent data, assessment of the recovery of fish stocks that undergo the most aggressive form of management, namely harvest moratoriums, remains a challenge. Large schools of red drum (Sciaenops ocellatus) were common along the northern Gulf of Mexico until the late 1980s when increased fishing effort quickly depleted the stock. After 24 years of harvest moratorium on red drum in federal waters, the stock is in need of reassessment; however, fisherydependent data are not available in federal waters and fishery-independent data are limited. We document the distribution, age composition, growth, and condition of red drum in coastal waters of the north central Gulf of Mexico, using data collected from a nearshore, randomized, bottom longline survey. Age composition of the fishery-independent catch indicates low mortality of fish age 6 and above and confirms the effectiveness of the federal fishing moratorium. Bottom longline surveys may be a cost-effective method for developing fishery-independent indices for red drum provided additional effort can be added to nearshore waters (<20 m depth). As with most stocks under harvest bans, effective monitoring of the recovery of red drum will require the development of fishery-independent indices. With limited economic incentive to evaluate non-exploited stocks, the most cost-effective approach to developing such monitoring is expansion of existing fishery independent surveys. We examine this possibility for red drum in the Gulf of Mexico and recommend the bottom longline survey conducted by the National Marine Fisheries Service expand effort in nearshore areas to allow for the development of long-term abundance indices for red drum

Red Drum and Spotted Seatrout Live-Release Tournament Mortality and Dispersal

Although catch-and-release fishing tournaments undoubtedly reduce mortality of target species, postrelease mortality and fish stockpiling at release sites remain common concerns related to these tournaments. The impacts of liverelease tournaments on freshwater species have been widely studied. However, research on estuarine sport fishes is lacking even though catch-and-release tournaments targeting these species are prevalent and popular recreational fisheries exist. Therefore, we estimated the post-weigh-in mortality and dispersal of Red Drum Sciaenops ocellatus and Spotted Seatrout Cynoscion nebulosus released from the 2016–2018 Alabama Deep Sea Fishing Rodeo live-weigh-in categories using acoustic telemetry. To concurrently estimate overall post-weigh-in mortality and dispersal, we used a Bayesian multistate model. Overall Red Drum post-weigh-in mortality (median = 6.12%; posterior credible interval [CrI] = 5.67–9.24%) was lower than overall Spotted Seatrout mortality (median = 30.63%; CrI = 26.74–40.00%). These estimates were within reported catch-and-release mortality ranges; however, they were higher than recent estimates for Spotted Seatrout. Within 1 week postrelease, Spotted Seatrout dispersal estimates (median = 87.03%; CrI = 72.96–95.72%) were higher than Red Drum (median = 55.62%; CrI = 42.75–68.10%) or Micropterus spp. in coastal and inland ecosystems. Long-term stockpiling at the release site was also not present; at the end of our 8-week observation period, median dispersal estimates were 94.41% (CrI = 87.15–98.19%) and 98.54% (CrI = 93.68–99.82%) for Red Drum and Spotted Seatrout, respectively. Red Drum fisheries may benefit most from live-release tournaments given that maximum mortality was \u3c10%, but Spotted Seatrout fisheries may also benefit, especially if considerations are made to further reduce tournament mortality. Although we do not know the ratio of tournament mortality to recreational harvest for these species, live-release tournaments may be able to relieve some harvest pressure on heavily exploited inshore marine fisheries and research validating their usefulness should continue

Participatory Conservation of Coastal Habitats: The Importance of Understanding Homeowner Decision Making to Mitigate Cascading Shoreline Degradation

Along densely populated coasts, the armoring of shorelines is a prevalent cause of natural habitat loss and degradation. This article explores the values and decision making of waterfront homeowners and identifies two interlinked and potentially reversible drivers of coastal degradation. We discovered that: (1) misperceptions regarding the environmental impacts and cost-effectiveness of different shoreline conditions was common and may promote armoring; and (2) many homeowners reported only altering their shorelines in response to damage caused by armoring on neighboring properties. Collectively, these findings suggest that a single homeowner’s decision may trigger cascading degradation along a shoreline, which highlights the necessity of protecting existing large stretches of natural shoreline. However, our study also found that most homeowners were concerned with environmental impacts and preferred the aesthetics of natural landscapes, both of which could indicate nascent support and pathways for conservation initiatives along residential shorelines

Development of a Low-Cost Arduino-Based Sonde for Coastal Applications

This project addresses the need for an expansion in the monitoring of marine environments by providing a detailed description of a low cost, robust, user friendly sonde, built on Arduino Mega 2560 (Mega) and Arduino Uno (Uno) platforms. The sonde can be made without specialized tools or training and can be easily modified to meet individual application requirements. The platform allows for internal logging of multiple parameters of which conductivity, temperature, and GPS position are demonstrated. Two design configurations for different coastal hydrographic applications are highlighted to show the robust and versatile nature of this sensor platform. The initial sonde design was intended for use on a Lagrangian style surface drifter that recorded measurements of temperature; salinity; and position for a deployment duration of less than 24 h. Functional testing of the sensor consisted of a 55 h comparison with a regularly maintained water quality sensor (i.e., YSI 6600 sonde) in Mobile Bay, AL. The temperature and salinity data were highly correlated and had acceptable RMS errors of 0.154 degrees C and 1.35 psu for the environmental conditions. A second application using the sonde platform was designed for longer duration (~3–4 weeks); subsurface (1.5–4.0 m depths) deployment, moored to permanent structures. Design alterations reflected an emphasis on minimizing power consumption, which included the elimination of the GPS capabilities, increased battery capacity, and power-saving software modifications. The sonde designs presented serve as templates that will expand the hydrographic measurement capabilities of ocean scientists, students, and teachers

Unintended Facilitation Between Marine Consumers Generates Enhanced Mortality for Their Shared Prey

We manipulated predator densities and prey vulnerability to explore how interactions between two predators affect overall mortality of their shared prey. Our threemember study system included eastern oysters (Crassostrea virginica) and two of its major consumers: southern oyster drills (Stramonita haemastoma) and stone crabs (Menippe adina). Field experiments demonstrated that drills and crabs foraging together generated higher than expected oyster mortality based on each species operating independently, even though crabs also killed some drills. In subsequent laboratory trials, we experimentally mimicked the handling of oysters by foraging crabs and confirmed that crabs facilitated drills by breeching oyster valves, thereby granting easy access for drills to their prey. Facilitation between cooccurring predators is uncommon and typically occurs because the behavior or habitat selection of a prey species is altered by the presence of one predator, consequently making the prey more susceptible to another predator. Whereas oysters are sedentary regardless of the predator field, we observed an entirely different mechanism that resulted in predator facilitation. This involved direct attacks on the physical defenses of oysters by one predator that ultimately increased the overall consumption rate of foraging species. These dynamics significantly enhanced mortality risk for a foundation species within an estuarine ecosystem

Seasonal Variability in Ichthyoplankton Abundance and Assemblage Composition in the Northern Gulf of Mexico off Alabama

Multiyear ichthyoplankton surveys used to monitor larval fish seasonality, abundance, and assemblage structure can provide early indicators of regional ecosystem changes. Numerous ichthyoplankton surveys have been conducted in the northern Gulf of Mexico, but few have had high levels of temporal resolution and sample replication. In this study, ichthyoplankton samples were collected monthly (October 2004–October 2006) at a single station off the coast of Alabama as part of a long-term biological survey. Four seasonal periods were identified from observed and historic water temperatures, including a relatively long (June–October) “summer” period (water temperature \u3e26°C). Fish egg abundance, total larval abundance, and larval taxonomic diversity were significantly related to water temperature (but not salinity), with peaks in the spring, spring–summer, and summer periods, respectively. Larvae collected during the survey represented 58 different families, of which engraulids, sciaenids, carangids, and clupeids were the most prominent. The most abundant taxa collected were unidentified engraulids (50%), sand seatrout (Cynoscion arenarius, 7.5%), Atlantic bumper (Chloroscombrus chrysurus, 5.4%), Atlantic croaker (Micropogonias undulatus, 4.4%), Gulf menhaden (Brevoortia patronus, 3.8%), and unidentified gobiids (3.6%). Larval concentrations for dominant taxa were highly variable between years, but the timing of seasonal occurrence for these taxa was relatively consistent. Documented increases in sea surface temperature on the Alabama shelf may have various implications for larval fish dynamics, as indicated by the presence of tropical larval forms (e.g., fistularids, labrids, scarids, and acanthurids) in our ichthyoplankton collections and in recent juvenile surveys of Alabama and northern Gulf of Mexico seagrass habitats