Harms-Tuohy, Cheksea A.

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    The management and feeding ecology of the invasive lionfish (Pterois volitans) in Puerto Rico
    (2016) Harms-Tuohy, Cheksea A.; Appeldoorn, Richard S.; College of Arts and Sciences - Sciences; Schizas, Nikolaos; Weil, Ernesto; Turingan, Ralph; Otero, Ernesto; Department of Marine Sciences; Grove, Kurt
    Since the mid-1980s, two Indo-Pacific lionfishes, Pterois volitans and P. miles, have established a significant presence in the Western North Atlantic, including the Caribbean Sea and the Gulf of Mexico. The first documented report of lionfish (Pterois volitans) in Puerto Rico occurred in 2008, and these predatory fish were first observed in La Parguera a year later. In general, lionfish are professed to significantly affect ecosystem function and associated ecosystem services. This threat and the perceived negative impact of invasive lionfish on the marine ecosystems in the Western North Atlantic and Caribbean accentuate the need for sustained research on their biological and ecological dynamics. Removal efforts are an effective means of reducing lionfish densities, yet most studies fail to address the reaction of the native fish communities in response to these removals. Furthermore, assessing impacts should also involve investigating the feeding ecology to characterize the dietary profile of lionfish as their diets have been shown to be site specific. The main purpose of this five year study was to investigate the perceived impacts of lionfish by determining the real impacts on native fish communities in Puerto Rico by addressing the following objectives: 1) characterize the dietary profile of the lionfish using next generation sequencing, 2) determine the digestion rate of fish and shrimp prey items, with recommendations for future feeding ecology studies and 3) assess the effectiveness of a small-scale dedicated lionfish removal and the response of the native predators and prey. The major disadvantage of morphological identification and DNA barcoding is the inability to utilize the digested material. However, next generation sequencing (i.e., DNA metabarcoding) can analyze all components of the gut contents, including the previously unidentifiable portion. Sixty-three lionfish were caught from the inshore and offshore reefs of La Parguera and stomach contents were separated into two sample regimes – a liquid (i.e., digested) and a tissue. A 313bp region of the cytochrome oxidase subunit I (COI) gene was amplified from extracted DNA and samples were sequenced with Illumina MiSeq. The resulting sequences were compared to known databases to identify specimens to the lowest taxon. Thirty-nine fish species from 16 families were identified (35 each in the digested and tissue fractions), including members of Pomacentridae, Acanthuridae, Gobiidae, Apogonidae and Scaridae. Utilizing the digested material proved efficient in detecting prey species, especially those that would have been missed with traditional methods. Furthermore, prey species lists and frequencies of fish of different size. Identifying a partially digested prey item via morphological identification is highly dependent on the digestive level of the prey item. This study analyzed the digestion rate of known teleost and invertebrate prey items in lionfish stomachs, over set time intervals, to provide an estimate of time to digestion for these prey types. Two size classes of lionfish were examined and digestion of prey items were ranked. Approximately 4 hours were required before a fish prey item was unrecognizable at the species level, and 5 hours for shrimp. Predator size, prey type and time since ingestion were observed to predict digestion rank of the prey items. Temperature was not correlated with digestion, by effect of the experimental design. Furthermore, a detailed prey digestion scale was developed for shrimp and recommendations were provided to maximize prey identification obtained using morphological gut content analyses. Pelotas reef, a inshore linear coral reef in La Parguera, was an ideal location for the small-scale removal experiment as the size mimicked that of the near-shore, culled marine protected area in Rincón (Tres Palmas). Pelotas had a small lionfish population that was not targeted by the dive industry or local fishermen prior to the study. Three removal events over a one month period reduced lionfish densities in this 0.6 km area. Nine months were required for densities to return, although lionfish biomass was still reduced. The absence of tagged lionfish and the observed small sizes in post-removal months suggests re-colonization occurred via ontogenetic migration rather than lateral immigration by adults from nearby reefs. Contrary to what was anticipated given the perceived impacts, no detectable effects of the removal were observed on native prey or piscivore fish. This project demonstrated that while removals are an effective means of controlling lionfish, native fish abundance is not impacted when lionfish densities are relatively low. Removal efforts with the goal of increasing native biodiversity will need to consider these factors before committing resources to this strategy.