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Objective: Cutaneous ulcerative skin lesions in a complex of invasive Gulf of Mexico lionfish (Red Lionfish Pterois volitans, Devil Firefish P. miles, and the hybrid Red Lionfish × Devil Firefish) became epizootic beginning in mid‐August 2017. Herein, we provide the first pathological descriptions of these lesions and summarize our analyses to elucidate the etiology of the disease. Methods: We examined ulcerated and normal fish through gross pathology and histopathology, bacterial sampling, and unbiased metagenomic next‐generation sequencing. We tracked prevalence of the disease, and we used biological health indicators (condition factor, splenosomatic and hepatosomatic index) to evaluate impacts to health, while considering sex and age as potential risk factors. Result: Typical ulcerative lesions were deep, exposing skeletal muscle, and were bordered by pale or reddened areas often with some degree of scale loss. Only incidental parasites were found in our examinations. Most fish (86%; n = 50) exhibited wound healing grossly and histologically, confirmed by the presence of granulation tissues. A primary bacterial pathogen was not evident through bacterial culture or histopathology. Metagenomic next‐generation sequencing did not reveal a viral pathogen (DNA or RNA) but did provide information about the microbiome of some ulcerated specimens. Compared with clinically healthy fish, ulcerated fish had a significantly lower condition factor and a higher splenosomatic index. Disease prevalence at monitored sites through July 2021 indicated that ulcerated fish were still present but at substantially lower prevalence than observed in 2017. Conclusion: Although some common findings in a number of specimens suggest a potential role for opportunistic bacteria, collectively our suite of diagnostics and analyses did not reveal an intralesional infectious agent, and we must consider the possibility that there was no communicable pathogen. Impact StatementAn outbreak of ulcers affected lionfish in the Gulf of Mexico. The disease occurred coincident to declines in invasive lionfish populations but could be contagious to native fish. Sick fish were examined to determine the cause. Findings were inconclusive but bacteria and environmental factors should be further investigated. [ABSTRACT FROM AUTHOR]

Invasive Indo-Pacific lionfish Pterois volitans/miles have become well-established in many western Atlantic marine habitats and regions. However, high densities and low genetic diversity could make their populations susceptible to disease. We examined changes in northern Gulf of Mexico (nGOM) lionfish populations following the emergence of an ulcerative skin disease in August 2017, when estimated disease prevalence was as high as 40%. Ulcerated female lionfish had 9% lower relative condition compared to non-ulcerated females. Changes in lionfish size composition indicated a potential recruitment failure in early summer 2018, when the proportion of new recruits declined by >80%. Remotely operated vehicle surveys during 2016–2018 indicated lionfish population density declined in 2018 by 75% on natural reefs. The strongest declines (77–79%) in lionfish density were on high-density (>25 lionfish per 100 m2) artificial reefs, which declined to similar levels as low-density (<15 lionfish per 100 m2) artificial reefs that had prior lionfish removals. Fisheries-dependent sampling indicated lionfish commercial spearfishing landings, commercial catch per unit effort (CPUE), and lionfish tournament CPUE also declined approximately 50% in 2018. Collectively, these results provide correlative evidence for density-dependent epizootic population control, have implications for managing lionfish and impacted native species, and improve our understanding of biological invasions. [ABSTRACT FROM AUTHOR]

The lionfish (Pterois volitans, P. miles) is the first known species of marine fish to invade the Caribbean and Gulf of Mexico, and it is threatening the biodiversity of the region´s coral reefs. Its success as an invasive species is due to its high predation and fertility, fast growth and lack of predators. Its first recorded appearance in Mexico was in 2009. Twenty-two sites were monitored around the reef of Banco Chinchorro Biosphere Reserve (BCBR), to estimate their abundance, during 2013. Densities from 0 to 333 ind ha-1 (97.6 ± 140.2 ind ha-1) and biomasses from 0 to 58.7 kg ha-1 (18.2 ± 29.9 kg ha-1) were recorded, the highest so far in the Mexican Caribbean. In addition, two lionfish distribution zones were detected: leeward reef (LR) and windward reef (WR). LR was 4.6 and 3.9 times higher in density and biomass than WR, respectively. The sizes found in the monitoring ranged from 5 to 40 cm of total length. Finally, a gregarious behavior was observed in 47.5% of the recorded fish. Our results suggest that to prevent the development of large reservoirs of lionfishes in the BCBR, management and control actions in areas of high lionfish abundance should be prioritized. [ABSTRACT FROM AUTHOR]

Abstract 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 <100% removal efficiency, in concert with density-dependent processes, may explain recent findings that sustained lionfish removal efforts had no discernible positive impacts on native reef fish communities. [ABSTRACT FROM AUTHOR]

Despite the devastating impact of the lionfish (Pterois volitans) invasion on NW Atlantic ecosystems, little genetic information about the invasion process is available. We applied Genotyping by Sequencing techniques to identify 1,220 single nucleotide polymorphic sites (SNPs) from 162 lionfish samples collected between 2013 and 2015 from two areas chronologically identified as the first and last invaded areas in US waters: the east coast of Florida and the Gulf of Mexico. We used population genomic analyses, including phylogenetic reconstruction, Bayesian clustering, genetic distances, Discriminant Analyses of Principal Components, and coalescence simulations for detection of outlier SNPs, to understand genetic trends relevant to the lionfish’s long-term persistence. We found no significant differences in genetic structure or diversity between the two areas (FST p-values>0.01, and t-test p-values>0.05). In fact, our genomic analyses showed genetic homogeneity, with enough gene flow between the east coast of Florida and Gulf of Mexico to erase previous signals of genetic divergence detected between these areas, secondary spreading, and bottlenecks in the Gulf of Mexico. These findings suggest rapid genetic changes over space and time during the invasion, resulting in one panmictic population with no signs of divergence between areas due to local adaptation. [ABSTRACT FROM AUTHOR]

Background. Biological invasions represent a threat to the ecological stability of the ecosystem. Two lionfish species, the red lionfish and the devil fi refish--both tropical marine predators native to the Indo-Pacific--were introduced to the Atlantic Ocean. However, only one--the red lionfish, Pterois volitans (Linnaeus, 1758)--has reached the level of an invasive species so far. It is crucial to learn its biology and ecology to understand trends of its invasion and impacts on native fauna, and to determine ecological changes as the invasion progresses. This study reports the growth and mortality of P. volitans in coral reefs of the Parque Nacional Arrecife Alacranes, off the northern Yucatan Peninsula, Mexico, in Southern Gulf of Mexico. Materials and methods. Lobster diver fi shers participated in voluntary captures of lionfish during the lobster fi shing seasons of 2010-2012. In the laboratory, lionfish were taxonomically identified, measured, and weighed. Their length-weight relation was determined according to the commonly used equation: W = aTLb. Fish total lengths were used to calculate the parameters of the von Bertalanffy growth function (VBGF) of lionfish based on the size-frequency analysis routine ELEFAN in the FiSAT II software. Results. A total of 776 lionfish (9.0 to 38.9 cm in total length, 7 to 874 g in total wet weight) were collected. The VBGF parameters estimated were L8 = 42 cm, K = 0.88-1, t0 = -0.107 years. The total mortality instantaneous rate (Z) calculated by the total length converted catch curve was 2.06 year-1. Conclusion. This study provides fi rst calculation of growth parameters and mortality of P. volitans in Southern Gulf of Mexico as determined by size-frequency analysis. Results contribute to the knowledge on the biology of P. volitans and to a better understanding of aspects of its biological invasion in the region. [ABSTRACT FROM AUTHOR]