Pterois In Their Native Ranges? University of Guam Marine Laboratory
Why Are Lionfishes (Pterois, Scorpaenidae) So Rare In Their Native Ranges? Terry J. Donaldson, David Benavente and Roxie Diaz University of Guam Marine Laboratory UOG Station Mangilao, Guam 96923 USA email: [email protected] What is Rarity? • Species with low abundance • Species with small geographic ranges • Species that may be found only in a few specialized habitats • These components are not mutually exclusive A Fourth Definition • Species with wide geographical ranges but low adult abundances at any given locality Cheilinus undulatus (Labridae) Photos: J.E. Randall Bolbometopon muricatum Labridae: Scarinae What Causes Species to be Rare? • Relationship between body size and range size • Relationship between body size and abundance • Environmental adaptations resulting from range size variability at higher latitudes • Habitat requirements and resource availability • Poor ability to exploit marginal habitats or other resources • Poor mobility • Low reproductive effort • Poor recruitment After Gaston (1994); Jones, Munday and Caley (2002) The Unusual Suspects: Lionfishes (Pterois, Scoraenidae) Pterois antennata Photographs: J.E. Randall Pterois radiata Pterois volitans Why Are Scorpionfishes So Rare? Photographs: J.E. Randall and R.E. Myers Tropical and Subtropical Scorpionfishes • Some have a high degree of habitat specificity • Strong site fidelity because of poor mobility • Behavior • Ambush or hunting predators • Long larval life but poor recruitment? • Prey of larger predators limits abundance of adults and juveniles? • Sampling artifacts: cryptic and/or nocturnal Visual surveys at selected Pacific localities (n = 632 transects) Transect Type and Number Locality Guam Northern Mariana Islands (limestone) Northern Mariana Islands (volcanic) Palau Southwest Palau Islands Yap-Ulithi, Micronesia Chuuk, Micronesia Kosrae, Micronesia Kwajalein, Marshall Is. Majuro, Marshall Is. American Samoa Sta. Ysabella, Solomon Is. Visayas, Philippines Total Timed Swim GPS Timed 63 43 5 0 65 21 0 11 6 3 0 22 12 251 7 0 0 0 0 0 0 0 0 0 0 0 3 10 Belt 157 4 0 11 0 8 55 0 7 7 122 0 0 371 Number of transects out of a total of 632 transects where lionfishes were observed. Pant = Pterois antennata; Prad = P. radiata; Pvol = P. volitans. Transect type Pant Prad Timed GPS 0 0 0 Timed swim 3 5 23 Belt 3 0 3 Total 6 5 26 0.8% 4.1% Percent 1.9% Pvol What Causes Species to be Rare? • Relationship between body size and range size • Relationship between body size and abundance • Environmental adaptations resulting from range size variability at higher latitudes • Habitat requirements and resource availability • Poor ability to exploit marginal habitats or other resources • Poor mobility • Low reproductive effort • Poor recruitment Body Size, Range Size and Abundance • Species with wide geographical ranges but low adult abundances at any given locality Cheilinus undulatus Photos: J.E. Randall Bolbometopon muricatum Habitat Pterois antennata Pterios volitans Pterois radiata Pterois volitans Resource Use and Behavior • Lionfishes are social • Shelter together • Hunt cooperatively Resource Use: Being a Predator • Adults are piscivorous but also feed upon crustaceans • Nocturnal predators but also feeding during daylight and crepuscular periods (dusk and dawn “switchover”) • Prey limited? Doubtful. Long Larval Life and Poor Recruitment • Morphological and life history specializations of larvae facilitate long larval periods and greater dispersal • Wide geographic ranges • Why poor recruitment? Many larvae lost in “vastness” of the IndoWest Pacific? Predation upon larvae, post-larvae and small juveniles promotes low abundance locally? Prey of Larger Predators? • Largely anecdotal information or small sample sizes • Scorpaenids found in stomachs of groupers (some groupers not much larger than their prey) • Moray eels will prey opportunistically upon adults • But, how much larger? What preys upon postlarval juveniles? Poor Mobility and High Site Fidelity Scorpaenopsis macrochir Pterois volitans Pterois antennata Rarity, “crypticity”, nocturnal behavior and sampling error Turning the Question Around: Why Aren’t Lionfishes Rare in the Western Atlantic? Some Possible Explanations (But Not All) • Lack of effective predators upon adults • A surfeit of suitable habitat (= disturbed habitat) • The geography and physics of larval distribution • Lack of effective predators upon post-larval juveniles • Competitive release as invasive species • Altered states: shifts in life history strategies that promote rapid growth, early maturity and reproduction Acknowledgments • Jack Randall- B.P. Bishop Museum (photographs) • Robert Myers- Coral Graphics (photographs) • Surveys funded or supported directly or indirectly by: NOAA, U.S. Fish and Wildlife Service, U.S. National Park Service, U.S. Navy, The Nature Conservancy, and the University of Guam Marine Laboratory
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