Red porgy (Pagrus pagrus) is a reef-associated, economically-important, winter-spawning, protogynous Sparidae species that appears to have declined in abundance in recent years along the southeast ...United States Atlantic coast. We used spatially-explicit generalized additive models built with fishery-independent chevron trap (1990-2021) and video data (2011-2021) to quantify the ways in which red porgy relative abundance and mean size varied across temporal, spatial, environmental, and habitat variables. Mean red porgy relative abundance from traps declined by 77% between 1992 and 2021, and declines were similarly large (69%) on video between 2011 and 2021. The largest two-year decline in relative abundance occurred early in the COVID-19 pandemic (2019-2021)- 32% in traps and 45% on video-despite already low abundance. Highest red porgy relative abundance from traps and video occurred in deep areas (i.e., 60-100 m) between southern North Carolina and north Georgia, and red porgy preferred low relief but continuous hardbottom habitats (i.e., pavement). We confirmed recent low recruitment of red porgy in the region based on the large increase in mean length (29%) and severe (~99%) declines of juvenile red porgy caught over the 32-year trap survey. Evidence suggests that recruitment failure is partially or mostly responsible for red porgy abundance declines, and, moreover, the regulation of harvest is unlikely to achieve sustainable management goals until recruitment increases.
Abstract
Traps (or pots) are one of the oldest and most widespread scientific survey gears for fish and decapod crustaceans around the world. Here, I review and synthesize the extensive scientific ...literature describing the various benefits and drawbacks of using traps as a survey gear in scientific studies. The widespread use of traps in fish and decapod surveys is due to several characteristics like their low cost, flexible design, ease of use, ability to fish unattended, and being amenable to pairing with other gears. However, there are a number of significant drawbacks of using traps, including highly variable catches due to environmental fluctuations or behavioral interactions or lost traps that continue catching and killing animals, that must be considered and accounted for when initiating trap surveys. This study highlights the types of habitats and species most and least suited for monitoring by traps, and emphasizes the importance of matching the goals and objectives of a trap survey with the correct trap design, mouth entrance, bait type, soak time, and pairing of gears. Pilot studies are also recommended before surveys are initiated to quantify the selectivity patterns of traps and identify the various factors that may influence trap catch.
It is commonly assumed in surveys that the likelihood of capturing or observing individuals of a given species is constant. Yet evidence is building that catchability, or the likelihood of catching ...an individual present at a site, can vary.We used 5465 paired trap-video samples collected along the southeast US Atlantic coast in 2015−2018 to estimate trap catchabilities of 6 reef fish species (gray triggerfish Balistes capriscus, red porgy Pagrus pagrus, vermilion snapper Rhomboplites aurorubens, black sea bass Centropristis striata, red snapper Lutjanus campechanus, white grunt Haemulon plumierii) as the ratio of trap catch to standardized site abundance from corresponding videos. Species-specific trap catchabilities were then related to 2 primary predictor variables: water temperature and percent of the visible bottom consisting of rocky substrate. Water temperature strongly influenced trap catchabilities for all species after standardizing for all other variables. The 4 warm-water species displayed strong positive relationships between catchability and temperature; of these species, the smallest absolute increase in catchability occurred for vermilion snapper (0.0 at ~14°C to 0.05 at ~28°C) and the largest occurred for white grunt (0.0 at ~14°C to 0.49 at ~28°C). The 2 cooler-water species displayed either a dome-shaped (red porgy) or negative relationship (black sea bass) between catchability and temperature. Furthermore, trap catchabilities for all species declined substantially (42−80%) as the percent hard bottom of the site in - creased. Only when catchability is properly accounted for can results be considered unbiased and subsequent management advice be considered accurate.
Underwater video has become an important tool for monitoring reef fish populations worldwide because it is nonextractive and not strongly selective. A variety of approaches have been developed to ...enumerate fish on videos, but to our knowledge these metrics have not been tested to determine if they are proportional to true abundance. We compared the most commonly used metric, MaxN (i.e., the maximum number of fish in a single frame during the viewing interval), to a newly developed metric, MeanCount (i.e., the mean number of fish observed in a series of snapshots over a viewing interval), using simulations, a laboratory experiment, and an empirical study. MaxN was nonlinearly related to true abundance using all three approaches, providing increasingly dampened estimates of abundance with increasing true abundance (i.e., hyperstability). Therefore, MaxN may result in positively biased indices of abundance for declining fish stocks or negatively biased abundance indices when fish stocks are increasing. Alternatively, MeanCount was generally linearly related to true abundance and its variability was similar to MaxN, suggesting that MeanCount can be useful for indexing abundance of fish in underwater video surveys.
Extreme weather events strongly influence marine, freshwater, and estuarine ecosystems in myriad ways. We quantified movements of a demersal oceanic fish species (gray triggerfish Balistes capriscus; ...N = 30) before, during, and after two hurricanes in 2017 using fine-scale acoustic telemetry at a 37-m deep study site in North Carolina, USA. During storms, gray triggerfish movement and emigration rates were 100% and 2550% higher, respectively, than on days with no storms. We found that increased movement rates were much more strongly correlated with wave orbital velocity (i.e., wave-generated oscillatory flow at the seabed) than either barometric pressure or bottom water temperature, two covariates that have been demonstrated to be important for organisms in shallower water. Higher movement rates during storms were due to increased mobility at night, and emigrations typically occurred at night in the direction of deeper water. Overall, we found significant storm effects on the movement behavior of a demersal fish species in the open ocean, despite our study occurring in deeper water than previous studies that have examined storm effects on animal movement. We conclude that tropical storms are a driving force behind the structure of marine ecosystems, in part by influencing movements of mobile animals.
Occupancy models using incidence data collected repeatedly at sites across the range of a population are increasingly employed to infer patterns and processes influencing population distribution and ...dynamics. While such work is common in terrestrial systems, fewer examples exist in marine applications. This disparity likely exists because the replicate samples required by these models to account for imperfect detection are often impractical to obtain when surveying aquatic organisms, particularly fishes. We employ simultaneous sampling using fish traps and novel underwater camera observations to generate the requisite replicate samples for occupancy models of red snapper, a reef fish species. Since the replicate samples are collected simultaneously by multiple sampling devices, many typical problems encountered when obtaining replicate observations are avoided. Our results suggest that augmenting traditional fish trap sampling with camera observations not only doubled the probability of detecting red snapper in reef habitats off the Southeast coast of the United States, but supplied the necessary observations to infer factors influencing population distribution and abundance while accounting for imperfect detection. We found that detection probabilities tended to be higher for camera traps than traditional fish traps. Furthermore, camera trap detections were influenced by the current direction and turbidity of the water, indicating that collecting data on these variables is important for future monitoring. These models indicate that the distribution and abundance of this species is more heavily influenced by latitude and depth than by micro-scale reef characteristics lending credence to previous characterizations of red snapper as a reef habitat generalist. This study demonstrates the utility of simultaneous sampling devices, including camera traps, in aquatic environments to inform occupancy models and account for imperfect detection when describing factors influencing fish population distribution and dynamics.
Most demersal fishes are difficult to observe and track due to methodological and analytical constraints. We used an acoustic positioning system to elucidate the horizontal and vertical movements of ...44 red snapper (Lutjanus campechanus) off North Carolina, USA, in 2019. Mean movement rate and distance off bottom varied by individual, with larger red snapper generally moving faster and spending more time farther off the bottom than smaller individuals. We used generalized additive mixed models that accounted for temporal autocorrelation in the data to show that mean hourly red snapper movement rate was lower during the day than at night and was negatively related to bottom water temperature. Moreover, red snapper spent more time off the bottom during the day than at night, and vertical movements were mostly related to bottom upwelling events that sporadically occurred in May-July. Our results and previous observations suggest that red snapper feed primarily on benthic organisms at night, and display diel vertical migration (i.e., thermotaxis) up to warmer waters (when present) during the day to aid digestive efficiency. Movement is a central organizing feature in ecology, and the sustainable management of fish will benefit from a better understanding of the timing and causes of fish movement.
Approaches towards habitat conservation and restoration often include supplementing or enhancing existing, degraded, or lost natural habitats. In aquatic environments, a popular approach towards ...habitat enhancement is the introduction of underwater human-made structures or artificial reefs. Despite the nearly global prevalence of artificial reefs deployed to enhance habitat, it remains debated whether these structures function similarly to comparable natural reefs. To help resolve this question, we conducted a literature review and accompanying meta-analysis of fish community metrics on artificial reefs within the coastal ocean and made comparisons with naturally-occurring reference reefs (rocky reefs and coral reefs). Our findings from a synthesis of 39 relevant studies revealed that, across reef ecosystems, artificial reefs support comparable levels of fish density, biomass, species richness, and diversity to natural reefs. Additional analyses demonstrated that nuances in these patterns were associated with the geographic setting (ocean basin, latitude zone) and artificial reef material. These findings suggest that, while artificial reefs can mimic natural reefs in terms of the fish assemblages they support, artificial reefs are not one-size-fits-all tools for habitat enhancement. Instead, artificial reefs should be considered strategically based on location-specific scientific assessments and resource needs to maximize benefits of habitat enhancement.
Marine fish abundance and distribution often varies across spatial scales for a variety of reasons, and this variability has significant ecological and management consequences. We quantified the ...distribution of reef-associated fish species along the southeast United States Atlantic coast using underwater video survey samples (N = 4,855 in 2011-2014) to elucidate variability within species across space, depths, and habitats, as well as describe broad-scale patterns in species richness. Thirty-two species were seen at least 10 times on video, and the most commonly observed species were red porgy (Pagrus pagrus; 41.4% of videos), gray triggerfish (Balistes capriscus; 31.0%), black sea bass (Centropristis striata; 29.1%), vermilion snapper (Rhomboplites aurorubens; 27.7%), and red snapper (Lutjanus campechanus; 22.6%). Using generalized additive models, we found that most species were non-randomly distributed across space, depths, and habitats. Most rare species were observed along the continental shelf break, except for goliath grouper (Epinephelus itajara), which was found on the continental shelf in Florida and Georgia. We also observed higher numbers of species in shelf-break habitats from southern North Carolina to Georgia, and fewer in shallower water and at the northern and southern ends of the southeast United States Atlantic coast. Our study provides the first broad-scale description of the spatial distribution of reef fish in the region to be based on fishery-independent data, reinforces the utility of underwater video to survey reef fish, and can help improve the management of reef fish in the SEUS, for example, by improving indices of abundance.
Invasive lionfish pose an unprecedented threat to biodiversity and fisheries throughout Atlantic waters off of the southeastern United States, the Caribbean, and the Gulf of Mexico. Here, we employ a ...spatially replicated Before-After-Control-Impact analysis with temporal pairing to quantify for the first time the impact of the lionfish invasion on native fish abundance across a broad regional scale and over the entire duration of the lionfish invasion (1990-2014). Our results suggest that 1) lionfish-impacted areas off of the southeastern United States are most prevalent off-shore near the continental shelf-break but are also common near-shore and 2) in impacted areas, lionfish have reduced tomtate (a native forage fish) abundance by 45% since the invasion began. Tomtate served as a model native fish species in our analysis, and as such, it is likely that the lionfish invasion has had similar impacts on other species, some of which may be of economic importance. Barring the development of a control strategy that reverses the lionfish invasion, the abundance of lionfish in the Atlantic, Caribbean, and Gulf of Mexico will likely remain at or above current levels. Consequently, the effect of lionfish on native fish abundance will likely continue for the foreseeable future.
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