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Mitigating the negative impacts of invasive lionfish (Pterois volitans/miles complex) is a top priority for marine reef fisheries management, with human removals considered the most viable approach to population control. Control efforts via diver spearfishing removals have annually removed tens of thousands of lionfish throughout their invasive range, but the effectiveness of removal efforts to remove 100% or achieve target lionfish densities in a given reef system has not been fully evaluated. Accounting for detection and removal efficacy is necessary for developing and evaluating lionfish management targets, as population- and community-level effects of lionfish removals may be diminished by undetected lionfish remaining in the system. This study quantified lionfish detection, catchability, and removal efficiency to evaluate the effectiveness of lionfish surveys and removal efforts on northern Gulf of Mexico (nGOM) artificial and natural reefs. Detection was assessed during crepuscular and midday time periods via diver and remotely operated vehicle (ROV) video surveys, with covariates for time of day and survey methodology assessed using generalized linear mixed models. Catchability and removal efficiency were estimated via depletion models based on serial removals via spearfishing on 6 artificial reefs and 9 natural reefs. A priori, we had expected lionfish detection to be higher during crepuscular periods given lionfish in the Caribbean and in their native range have been shown to forage more actively away from reefs then. However, we found lionfish detection was not significantly different between midday and crepuscular periods. Survey methodology affected detection, with 24% fewer lionfish being detected via ROV surveys versus diver surveys at artificial reefs and 72% fewer lionfish detected via ROV surveys at natural reefs. Therefore, density estimates on nGOM natural reefs, which constitute of >99% of the region’s habitat, may be higher than previously reported and problematic for lionfish management. Mean catchability for spearfishing lionfish was 0.88 on artificial reefs and 0.69 on natural reefs standardized for area. Mean removal efficiency for the first removal event was 87% on artificial reefs and 67% on natural reefs, higher than removal efficiency computed for Caribbean reefs (47%). Incomplete detection and

We examined the potential for Gulf of Mexico red snapper (RS) behavior to bias count estimates collected with a remotely operated vehicle (ROV), towed camera sled (TCS), subsurface towed acoustic sled (TAS), or SCUBA diver at artificial reef sites. Near- (≤ 5 m), mid- (≤ 15 m), and far-field (≤ 100 m) responses were examined using stationary stereo cameras, a horizontal acoustic profiler, and three-dimensional acoustic telemetry, respectively. Survey gears were deployed sequentially for 15 min with each gear immediately preceded by a 15-min control period. Near-field data (mean RS min−1) indicated counts were 7.3 times higher with the diver present and 1.9 times higher with the ROV. The TCS had a significant interaction effect with time on mean RS count in the near- and mid-field, as well as depth and acceleration. The TAS had no effect on RS behavior at any scale. Far-field data showed no significant effect of any gear on mean RS distance to reef. Overall, results indicate RS respond neutrally to survey gears at medium (≤ 15 m) to large (≤ 100 m) spatial scales, but small-scale (≤ 5 m) spatial attraction may bias RS counts with benthic survey gears, primarily by individuals near the periphery of the surveyed area approaching the gear.

Recreational fishers discard millions of red snapper (Lutjanus campechanus) annually in the northern Gulf of Mexico (nGOM), resulting in significant foregone yield. We conducted simulation modeling to evaluate the potential for hook-size regulations to improve efficiency in the recreational red snapper fishery. First, we imposed a suite of candidate parameter sets, informed by recent empirical studies, within the 2015 red snapper assessment model to estimate contact-selectivity of recreational fleets in the northeastern or northwestern GOM. We then evaluated potential hook-size regulations by imposing a suite of candidate parameter sets on future contact-selectivity of each recreational fleet, conditional on likelihood-based estimates from the first simulation exercise. In the assessment model, maximum likelihood values improved when strongly domed contact-selectivity curves with peak size approximating the current minimum length limit were imposed in either the eastern or western recreational fleet. Simulation results indicate mandating large hook sizes could modestly increase retained catch for the eastern recreational fleet while dramatically reducing the number of red snapper discarded by either fleet. Realized benefits of hook-size regulations will depend upon future fisher retention behavior, such as the intensity of live high-grading, discard mortality reduction practices, such as venting and the use of descender devices, and changes to current management regulations.

a b s t r a c t Artificial reefs were deployed in the northeastern Gulf of Mexico (GOM) by the state of Florida's marine fisheries agency but not reported to the public in an attempt to create no-harvest refuges for exploited fishes. As part of a broader examination of the efficacy of this approach, a tagging study was conducted at a subset (n = 9) of these unreported artificial reefs to examine the likelihood that reef fishes would

The ability to estimate fish abundance accurately over a particular habitat is contingent upon the use of appropriate sampling methods. The objectives of this study were to compare the catch per unit area (A), length-specific bias, and relative catchability (q-ratio) of four different gear types for sampling red snapper (Lutjanus campechanus) over natural low-relief reef habitats on the inner continental shelf of the northern Gulf of Mexico. Specifically, our goal was to assess the overall performance of a standard otter trawl, a small fish trap, a chevron trap, and a stationary 4-camera underwater video array during six quarterly sampling cruises performed in 2004 and 2005. The sizes of snapper captured by trawls ranged from 30 to 250 mm total length (TL) (ages 0 and 1 yr). Trawls captured the most red snapper per unit area and had q-ratios of 3:1 to 5:1 relative to small fish traps for juvenile red snapper. The chevron trap collected the second highest number of red snapper and proved most useful at collecting red snapper from 150 to 440 mm TL (ages 1–5 yr). The q-ratio of the chevron trap relative to the underwater video array was approximately 3:1. Our comparison demonstrated the chevron trap is most effective for sampling adults, while trawls were the most effective gear for sampling age-0 yr fish.