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Lionfish, native to reef ecosystems of the tropical and sub-tropical Indo-Pacific, were introduced to Florida waters in the 1980s, and have spread rapidly throughout the northwestern Atlantic, Caribbean Sea and the Gulf of Mexico. These invasive, carnivorous fish significantly reduce other fish and benthic invertebrate biomass, fish recruitment, and species richness in reef ecosystems. Fisheries resource managers have proposed the establishment of a commercial fishery to reduce lionfish populations and mitigate adverse effects on reef communities. The potential for a commercial fishery for lionfish is the primary reason to identify locations where lionfish accumulate sufficient amounts of ciguatoxin (CTX) to cause ciguatera fish poisoning (CFP), the leading cause of non-bacterial seafood poisoning associated with fish consumption. To address this issue, an initial geographic assessment of CTX toxicity in lionfish from the Caribbean and Gulf of Mexico was conducted. Lionfish samples (n = 293) were collected by spearfishing from 13 locations (74 sampling sites) around the Caribbean and Gulf of Mexico between 2012 and 2015. The highest frequencies of lionfish containing measurable CTX occurred in areas known to be high-risk regions for CFP in the central to eastern Caribbean (e.g., 53% British Virgin Islands and 5% Florida Keys). Though measurable CTX was found in some locations, the majority of the samples (99.3%) contained CTX concentrations below the United States Food and Drug Administration guidance level of 0.1 ppb Caribbean ciguatoxin-1 (C-CTX-1) equivalents (eq.). Only 0.7% of lionfish tested contained more than 0.1 ppb C-CTX-1 eq. As of 2018, there has been one suspected case of CFP from eating lionfish. Given this finding, current risk reduction techniques used to manage CTX accumulating fish are discussed.

The harmful algal bloom species, Karenia brevis, forms annual, often intense blooms in the Gulf of Mexico, particularly along the west Florida shelf. Though the ability of K. brevis blooms to cause mass mortalities in juvenile fish are well documented, the direct effect of bloom concentrations on larval fish has not been studied extensively. To better understand the potential effect of K. brevis on larval fish survival, laboratory spawned red porgy (Pagrus pagrus) larvae from 4–26 days post-hatch were exposed to concentrations of K. brevis observed in the field for either 24 or 48 h. This species is representative of fish which spawn in regions of the Gulf of Mexico and whose larvae are epipelagic and may encounter K. brevis blooms. In this study, three different K. brevis strains varying in the amount of brevetoxin produced were tested. Larval survivorship was found to be inversely proportional to the amount of brevetoxin produced by each strain. The EC50 value from the combined 24 h experiments was ~163,000 K. brevis cells L−1, which corresponds to cell concentrations found in moderately dense blooms. Larval mortality also increased substantially in the 48 h versus 24 h exposure treatments. These findings indicate K. brevis blooms have the potential to contribute to natural mortality of fish larvae and further reduce inter-annual recruitment of fishery species whose stocks in the Gulf of Mexico may already be depleted.

This paper describes a non-traditional fisheries management concept and an indicator-based framework to encourage and guide management of invasive lionfish (Pterois spp.) fisheries in the temperate and tropical western Atlantic. We introduce the concept of optimum lionfish yield (OLY)—an extension of the concept of ecologically sustainable yield—which considers local ecological health in the establishment of fishery management targets. In contrast to traditional fishery targets, OLY is a target exceeding maximum sustainable yield (MSY) that still provides relatively high sustainable yield, but further contributes to population suppression beyond what is achievable through targets at or below MSY. Thus, OLY seeks to balance management trade-offs from both natural resource and invasive species management perspectives. In this study, we developed an age-structured population model and applied the concept of OLY to quantify targets to initiate management of a nationally-managed lionfish fishery in Belize. Socioeconomic and ecological data were used as indicators to formulate OLY values. The model indicates that lionfish in Belize are biologically robust to fishing pressure, which corroborates previous findings. Fishing lionfish at rates above MSY levels is expected to substantially reduce population abundance, much more so than fishing at rates below MSY levels, while having relatively minimal impacts on yield. Population suppression can be further enhanced by reducing size at selection, but this is expected to be done at a significant cost to landings. Together, these data support continued establishment of (managed) commercial lionfish fisheries throughout the invaded range to provide an alternative sustainable fishery resource and serve as a means of national- and international-level control. While the concept and framework described here is introduced for management of invasive lionfish, it could be applied to management of other invasive species, both aquatic and terrestrial.

Numerous location-based diet studies have been published describing different aspects of invasive lionfish (Pterois volitans and Pterois miles) feeding ecology, but there has been no synthesis of their diet composition and feeding patterns across regional gradients. 8125 lionfish stomachs collected from 10 locations were analyzed to provide a generalized description of their feeding ecology at a regional scale and to compare their diet among locations. Our regional data indicate lionfish in the western Atlantic are opportunistic generalist carnivores that consume at least 167 vertebrate and invertebrate prey species across multiple trophic guilds, and carnivorous fish and shrimp prey that are not managed fishery species and not considered at risk of extinction by the International Union for Conservation of Nature disproportionately dominate their diet. Correlations between lionfish size and their diet composition indicate lionfish in the western Atlantic transition from a shrimp-dominated diet to a fish-dominated diet through ontogeny. Lionfish total length (TL) (mm) was found to predict mean prey mass per stomach (g) by the following equation mean prey mass =0.0002*TL1.6391, which can be used to estimate prey biomass consumption from lionfish length-frequency data. Our locational comparisons indicate lionfish diet varies considerably among locations, even at the group (e.g., crab) and trophic guild levels. The Modified Index of Relative Importance developed specifically for this study, calculated as the frequency of prey a × the number of prey a, can be used in other diet studies to assess prey importance when prey mass data are not available. Researchers and managers can use the diet data presented in this study to make inference about lionfish feeding ecology in areas where their diet has yet to be described. These data can be used to guide research and monitoring efforts, and can be used in modeling exercises to simulate the potential effects of lionfish on marine food webs. Given the large variability in lionfish diet composition among locations, this study highlights the importance of continued location-based diet assessments to better inform local management activities.