University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln USGS Staff -- ubP lished Research US Geological Survey 7-12-2006 Anguilliform larvae collected off orN th Carolina Steve W. Ross Center for Marine Science, University of North Carolina, [email protected] Tara L. Casazza Center for Marine Science, University of North Carolina Andrea M. Quattrini Florida Integrated Science Center, Center for Aquatic Resource Studies, United States Geological Survey, Kenneth J. Sulak Florida Integrated Science Center, Center for Aquatic Resource Studies, United States Geological Survey Follow this and additional works at: http://digitalcommons.unl.edu/usgsstaffpub Part of the Geology Commons, Oceanography and Atmospheric Sciences and Meteorology Commons, Other Earth Sciences Commons, and the Other Environmental Sciences Commons Ross, Steve W.; Casazza, Tara L.; Quattrini, Andrea M.; and Sulak, Kenneth J., "Anguilliform larvae collected off orN th Carolina" (2006). USGS Staff -- Published Research. 1063. http://digitalcommons.unl.edu/usgsstaffpub/1063 This Article is brought to you for free and open access by the US Geological Survey at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in USGS Staff -- ubP lished Research by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Mar Biol (2007) 150:681–695 DOI 10.1007/s00227-006-0388-z RESEARCH ARTICLE Anguilliform larvae collected off North Carolina Steve W. Ross Æ Tara L. Casazza Æ Andrea M. Quattrini Æ Kenneth J. Sulak Received: 17 February 2006 / Accepted: 18 May 2006 / Published online: 12 July 2006 Ó Springer-Verlag 2006 Abstract The distinctive larval stage of eels (lepto- individuals, ten species). Nine taxa accounted for 70% cephalus) facilitates dispersal through prolonged life in of the overall leptocephalus catches (in order of the open ocean. Leptocephali are abundant and di- decreasing abundance): Paraconger caudilimbatus verse off North Carolina, yet data on distributions and (Poey), Gymnothorax ocellatus Agassiz complex, biology are lacking. The water column (from surface to Ariosoma balearicum (Delaroche), Ophichthus gomesii 1,293 m) was sampled in or near the Gulf Stream off (Castelnau), Callechelys muraena Jordan and Ever- Cape Hatteras, Cape Lookout, and Cape Fear, North mann, Letharchus aliculatus McCosker, Rhynchocon- Carolina during summer through fall of 1999–2005, and ger flavus (Goode and Bean), Ophichthus cruentifer leptocephali were collected by neuston net, plankton (Goode and Bean), Rhynchoconger gracilior (Gins- net, Tucker trawl, and dip net. Additional samples burg). The top three species represented 52% of the were collected nearly monthly from a transect across total eel larvae collected. Most leptocephali were col- southern Onslow Bay, North Carolina (from surface to lected at night (79%) and at depths > 45 m. Eighty 91 m) from April 2000 to December 2001 by bongo percent of the eels collected in discrete depth Tucker and neuston nets, Methot frame trawl, and Tucker trawls at night ranged from mean depths of 59–353 m. trawl. Overall, 584 tows were completed, and 224 of A substantial number (38% of discrete depth sample these yielded larval eels. The 1,295 eel leptocephali total) of larval eels were also collected at the surface collected (combining all methods and areas) repre- (neuston net) at night. Daytime leptocephalus distri- sented at least 63 species (nine families). Thirteen butions were less clear partly due to low catches and species were not known previously from the area. lower Tucker trawl sampling effort. While net avoid- Dominant families for all areas were Congridae (44% ance may account for some of the low daytime catches, of individuals, 11 species), Ophichthidae (30% of an alternative explanation is that many species of larval individuals, 27 species), and Muraenidae (22% of eels occur during the day at depths > 350 m. Larvae of 21 taxa of typically shallow water eels were collected at depths > 350 m, but additional discrete depth diel Communicated by J.P. Grassle, New Brunswick sampling is needed to resolve leptocephalus vertical distributions. The North Carolina adult eel fauna S. W. Ross (&) Æ T. L. Casazza Æ A. M. Quattrini (estuary to at least 2,000 m) consists of 51 species, 41% Center for Marine Science, University of North Carolina Wilmington, 5600 Marvin K. Moss Lane, Wilmington of which were represented in these collections. Many NC 28409, USA species of leptocephali collected are not yet known to e-mail: [email protected] have juveniles or adults established in the South Atlantic Bight or north of Cape Hatteras. Despite Gulf K. J. Sulak Æ S. W. Ross Florida Integrated Science Center, Center for Aquatic Stream transport and a prolonged larval stage, many of Resource Studies, United States Geological Survey, these eel leptocephali may not contribute to their 7920 Northwest 71st Street, Gainesville, FL 32653, USA respective populations. 123 682 Mar Biol (2007) 150:681–695 Introduction 2005). The lack of species level identifications and detailed distribution data hamper assessments of the The larval stage of Anguilliformes, the leptocephalus, complete life history of most eel species, including the is among the most morphologically and physiologically role of leptocephali in the oceanic plankton. distinct of all larval fishes. The most striking features of During recent cruises off North Carolina, we col- leptocephali are laterally compressed, transparent lected a large diversity of anguilliform larvae. Our bodies, fang-like teeth, well developed eyes, and large objectives were to: (1) describe the taxonomic com- sizes (50–100 mm total lengths common). All An- position of anguilliform larvae collected off North guilliformes spawn in oceanic waters and exhibit a Carolina, (2) document their relative abundances, size prolonged larval period, lasting several months to years structures, and depth distributions, and (3) compare (Smith 1989a). Although eel leptocephali are unlike the taxonomic composition of the oceanic larval pool adult eels, they can be readily identified to species with in this region to that of the known adult eel popula- the exceptions of very small ( < 10 mm TL) and tions. metamorphic specimens. Even so, many leptocephali await taxonomic treatment, several described larval types cannot yet be matched to adults, and their biol- Materials and methods ogy and ecology remain poorly known (Smith 1989a). Leptocephali are often transported great distances The water column in or near the Gulf Stream off Cape from spawning sites to habitats suitable for recruitment Hatteras, Cape Lookout, and Cape Fear, North Caro- of juveniles. These movements are difficult to track, lina (Fig. 1 and Table 2) was sampled during annual partly because exact spawning localities of most eel summer or fall cruises (August 1999, July 2000, August species are unknown. Eleven mesopelagic and coastal 2001, September 2001, August 2002, August 2003, June benthic anguilliform species may spawn in the Sargasso 2004, and October 2005). As part of a larger study, an Sea (Schmidt 1922; Kleckner and McCleave 1982; overall objective was to sample diverse fish and Wippelhauser et al. 1985; McCleave 1993; McCleave invertebrate taxa in many habitats; thus, eel lepto- and Miller 1994; Miller and McCleave 1994; Miller cephali were opportunistically collected during day- 1995, 2002). Other species (e.g., ophichthids) may light and at night using a variety of nets targeting spawn at the surface over the continental shelf off the depths from the surface to 1,293 m (Table 2). We also southeastern United States (Ross and Rohde 2003). incorporated leptocephalus data from a separate study Leptocephali can also be transported to areas where which sampled an inshore to offshore transect across recruitment is apparently unsuccessful, as evidenced by southern Onslow Bay, April 2000–December 2001 the lack of adult populations (Richardson and Cowen (Quattrini et al. 2005). Generally, all gears were towed 2004). Regardless of future recruitment success, the against the current at approximately 3.7 km h–1 ground combination of an extended larval period and the speed. northward flow of the Gulf Stream facilitates dispersal Several methods were used to sample surface wa- of leptocephali along the East Coast of the United ters. Frequent occurrences of Sargassum spp. in surface States and beyond. waters interfered with flow meters, preventing accurate Eel populations are extensive and diverse in coastal measures of water volume sampled and catch density and offshore waters of North Carolina. Fifty-one spe- calculations. A 1 · 3-m neuston net (6.4-mm mesh cies of adult eels from 12 families occupy a wide range body, 3.2-mm mesh tailbag), NN1, was towed in the of habitats from rivers to the continental slope in this upper meter of the water column for 30 min in 1999 area (S.W. Ross, unpublished data), and 15 of these and 15 min during all other years. This gear effectively species are restricted to depths > 200 m as adults collected larger leptocephali, but the mesh size of this (Table 1). Although eel leptocephali have been col- net eliminated smaller leptocephali ( < 25 mm). To lected frequently in ocean waters off North Carolina determine the extent to which smaller leptocephali and/or in the South Atlantic Bight (SAB) (Powles and may be missed in surface waters, we conducted limited Stender 1976; Powell and Robbins 1994, 1998; Govoni sampling off Cape Lookout during October 2005 using and Spach 1999; Powell et al. 2000; Quattrini et al. the NN1 frame fitted with a Tucker trawl net (1.59-mm 2005), they were often not identified to species. Data mesh net), designated NN3. A 1-m diameter plankton on vertical distributions and distributions relative to net (505-lm mesh), PN, was towed for 30 min on the water masses (e.g., Gulf Stream) are also lacking for surface during 2002–2004 cruises. One metamorphic larval eels in this area or have been noted only at the specimen was collected at the surface by dip net during family level (Govoni and Spach 1999; Quattrini et al.