Comparisons of Open Ocean, Surface Fish Communities off North Carolina in Two Habitats: Sargassum versus Open Water Tara L. Casazza and Steve W. Ross Center for Marine Science, University of North Carolina Wilmington Table 2. Catch data for fishes collected off NC Figure 2. Numbers of individual fish per kilogram Sargassum for INTRODUCTION during summers of 1999-2003, *=significant. neuston net collections off NC. 3500 In the western North Atlantic pelagic Sargassum forms a dynamic floating habitat that supports a All Catch Data S OW 2000-2003 # of samples 109 137 3000 diverse assemblage of marine organisms, including fishes, invertebrates, sea turtles, marine birds and # of species 73 76 2500 R2 = 0.6695 marine mammals. Sargassum habitat serves as a primary nursery area for many juvenile fishes, some of # of individuals 17905 3603 2000 which are commercially important species (dolphinfish, jacks, amberjacks). Several studies have NN Catch Data (2000-2003) 1500 documented fishes associated with pelagic Sargassum, yet most of these studies were descriptive # of samples 43 75 1000 surveys and lacked data on ecological aspects of the community. Additionally, no studies have Stephanolepis hispidus Caranx crysos Cheilopogon melanurus # of species 55 54 500 compared Sargassum and adjacent open water communities. Although diets have been documented for # of individuals 13276 2240 Numbers of individuals 0 a few Sargassum-associated fish species, data are lacking for the majority of fish species in this mean # of spp. 10* 4 -55 1525354555657585 community. The objectives of this study are to acquire a more complete picture of the community mean # of indiv. 309* 30 Wet weight of Sargassum (kg) structure, feeding habits and behaviors of fishes collected in Sargassum and open water habitats using Figure 3. Pie charts of the percent volumes of food items found in the stomachs of dominant fish species collected in multiple sampling methods. Sargassum and open water habitats off NC. Additional data are being analyzed.

Open water Caranx crysos Open water Coryphaena hippurus Open water Cheilopogon melanurus (n=5) (n=17) (n=7) OTHER 3 CNIDARIA CHAETOGNATHS CRUSTACEA Sargassum ITEMS 0.7% 2.0% 3.5% 1.4% 10.0% AMPHIPODS Seriola fasciata Coryphaena hippurus Histrio histrio 4.4%

CHAETOGNATHS Table 1. Numbers of individuals collected in Sargassum and open water 23.9%23.

habitats off North Carolina during summers of 1999-2003. COPEPODS 68.2% Species S OW Species S OW FISH COPEPODS 88.0% Ablennes hians 15 14 Hyporhamphus unifasciatus 01 97.9% Abudefduf saxatilis 51 0 Istiophorus platypterus 444 Ahlia egmontis 41 Katsuwonus pelamis 02 Alectis ciliaris 04 Kyphosus incisor 61 Aluterus heudelotii 71 6 Kyphosus sectatrix 30 2 Sargassum Caranx crysos Sargassum Coryphaena hippurus Sargassum Cheilopogon melanurus Aluterus monoceros 38 4 Lagocephalus lagocephalus 10 (n=38) (n=55) (n=16) CHAETOGNATHS Aluterus schoepfii 16 15 Lobotes surinamensis 13 1 CHAETOGNATHS 1.6% OTHER 3 OTHER 3 ITEMS Aluterus scriptus 32 16 Makaira nigricans 01 5.0% CRUSTACEA ITEMS CRUSTACEA 2.0% 2.5% <1% 15.3% Argyropelecus aculeatus 10 Monacanthus ciliatus 144 46 Sargassum Balistes capriscus Auxis thazard 20 Monacanthus tuckeri 11 7 Parexocoetus brachypterus 7.4% Balistes capriscus 353 67 Mugil curema 18 COPEPODS Bryx dunckeri 81 Mullodichthys martinicus 10 COPEPODS 16.9% COPEPODS 37.0% FISH Cantherhines macrocerus 52 Myctophum affine 225 CRUSTACEA CHAETOGNATHS 51.0% METHODS 31.7% 71.0% Cantherhines pullus 13 4 Myctophum obtusirostre 010 58.0% Canthidermis maculata 19 0 Myctophum punctatum 14 • Surface waters in or near the Gulf Stream off NC were sampled for fishes during summers of 1999- Canthidermis sufflamen 21 7 Myctophum selenops 01 2003; 2 underwater video stations in 1999 Caranx bartholomaei 40 Oxyporhamphus micropterus 75 53 Caranx crysos 1655 521 Parexocoetus brachypterus 203 201 Caranx lugubris 30 Platybelone argalus 32 • Specimens collected by small mesh neuston net (1 x 3 m), dip net, hook & line, long line Caranx ruber 51 8 Prognichthys occidentalis 69 81 Figure 4. Pie charts of the percent volumes of food items found in the stomachs of fish species collected in Sargassum Carcharhinus falciformis 10 Psenes cyanophrys 50 habitat off NC. Cheilopogon cyanopterus 512 Pseudupeneus maculatus 31 • Fishes sorted from algae and preserved at sea, algae weighed and discarded Sargassum Stephanolepis hispidus Sargassum Balistes capriscus Sargassum Abudefduf saxatilis Cheilopogon exsiliens 37 Remora osteochir 10 (n=18) (n=17) (n=28) Cheilopogon furcatus 48 Scomber japonicus 027 CRUSTACEA PTEROPODS • Fishes identified, measured, weighed and preserved 6.0% Cheilopogon melanurus 475 291 Scomber scombrus 06 EGGS 0.4% 2.8% Chilomycterus sp. 01 Selar crumenophthalmus 45 CRUSTACEA COPEPODS • Mean # of individuals and spp. compared in open water and Sargassum habitats Clupea harengus 0216 Selene setapinnis 11 15.1% 20.2% Coryphaena equiselis 18 9 Selene vomer 03 FISH • Stomachs removed from dominant spp., commercially important spp. and endemic spp. Coryphaena hippurus 147 53 Seriola dumerili 10 28.6% EGGS 30.0% Cyclothone sp. 10 Seriola fasciata 60 6 COPEPODS Cypselurus comatus 02 Seriola rivoliana 38 4 64.0% Hippocampus erectus Exocoetus obtusirostris COPEPODS • Stomach contents identified to lowest practical taxa, enumerated, measured volumetrically Decapterus punctatus 164 153 Seriola sp. 265 26 82.1%82.1% EGGS CRUSTACEA 26.1% Diaphus dumerilii 10 Seriola zonata 41 24.7% • Diet composition analyzed for %N, %V, %F Diodon holocanthus 82 Sphyraena barracuda 01 Diodon hystrix 14 Sphyraena borealis 10 • Stomach contents supplemented with stable δ13C & δ15N isotope data for selected spp. Echeneis naucrates 21 Stephanolepis hispidus 13499 1450 Elagatis bipinnulata 22 2 Stephanolepis setifer 10 Sargassum Seriola species Sargassum Kyphosus sectatrix Sargassum Histrio histrio (n=35) (n=9) Euleptorhamphus velox 12 17 Synagrops bellus 01 (n=18) CHAETOGNATHS OTHER 2 Exocoetus obtusirostris 13 Syngnathus louisianae 10 OTHER 3 0.5% ITEMS ITEMS CRUSTACEA Fistularia tabacaria 11 Syngnathus pelagicus 16 1 <1.0% COPEPODS <1% 14.3% Gempylus serpens 03 Synodus synodus 01 6.9% CRUSTACEA Hemiramphus balao 27 5 Trachinotus carolinus 02 26.3% Hemiramphus brasiliensis 19 19 Trachinotus falcatus 01 Hippocampus erectus 77 Tylosurus acus 30 6 FISH CRUSTACEA CHAETOGNATHS Hippocampus reidi 11 Tylosurus crocodilus 10 FISH 35.4% 57.1% COPEPODS 52.9% 73.3% COPEPODS Hirundichthys affinis 30 23 Vinciguerria poweriae 01 32.9% 0.4% Histrio histrio 23 0 Xanthichthys ringens 02 Canthidermis sufflamen Holocentrus sp. 0 1 Total n 17905 3603 Lobotes surimanensis 1 x 3 m neuston net

Figure 1. Collection sites for fishes in Sargassum and open water habitats off NC during summers of 1999-2003. DIET DATA • 484 stomachs analyzed to date representing 23 fish species • 88% of all stomachs analyzed contained food items, 53 total food items identified Monacanthus ciliatus Oxyporhamphus micropterus Kyphosus sectatrix • Overall: 13 spp. of copepods, 3 spp. of shrimp, 10 spp. of fish were identified • Parasites (digenean trematodes & nematodes) observed in 44% of all stomachs

FOOD ITEMS

Diodon holocanthus Istiophorus platypterus Caranx bartholomaei COMMUNITY STRUCTURE DATA Leander tenuicornis Portunus sayi copepods eggs • 17,905 fishes (73 spp.) collected from 109 Sargassum stations, 13,276 fishes (55 spp.) from 43 neuston tows • 3603 fishes (76 spp.) collected from 137 open water stations, 2240 fishes (54 spp.) from 75 neuston tows ACKNOWLEDGEMENTS This research was partially funded by grants from the NOAA Office of Ocean Exploration • For neuston net collections, #s of individuals & #s of spp. significantly higher in Sargassum habitat (to S.W. Ross, lead Principle Investigator) and the North Carolina State Legislature. We would • Positive relationship between quantity of Sargassum and #s of individuals like to thank USGS for field support.