The relative value of different estuarine nursery areas in North Carolina for transient juvenile marine fishes

Offshore winter-spawned fishes dominate the nekton of south-eastern United States estuaries. Their juveniles reside for several months in shallow, soft bottom estuarine creeks and bays called primary nursery areas. Despite similarity in many nursery characteristics, there is, between and within species, variability in the occupation of these habitats. Whether all occupied habitats are equally valuable to individuals of the same species or whether most recruiting juveniles end up in the best habitats is not known. If nursery quality varies, then factors controlling variation in pre-settlement fish distribution are important to year-class success. If nursery areas have similar values, interannual variation in distribution across nursery creeks should have less effect on population sizes or production. I used early nursery period age-specific growth and mortality rates of spot (Leiostomus xanthurus) and Atlantic croaker (Micropogonias undulatus)—two dominant estuarine fishes—to assess relative habitat quality across a wide variety of nursery conditions, assuming that fish growth and mortality rates were direct reflections of overall physical and biological conditions in the nurseries. I tested the hypothesis that habitat quality varies for these fishes by comparing growth and mortality rates and distribution patterns across a wide range of typical nursery habitats at extreme ends of two systems. Juvenile spot and Atlantic croaker were collected from 10 creeks in the Cape Fear River estuary and from 18 creeks in the Pamlico Sound system, North Carolina, during the 1987 recruitment season (mid-March–mid-June). Sampled creeks were similar in size, depth, and substrates but varied in salinities, tidal regimes, and distances from inlets. Spot was widely distributed among all the estuarine creeks, but was least abundant in the creeks in middle reaches of both systems. Atlantic croaker occurred in the greatest abundance in oligohaline creeks of both systems. Instantaneous growth rates derived from daily otolith ages were generally similar for all creeks and for both species, except that spot exhibited a short-term growth depression in the upriver Pamlico system creeks—perhaps the result of the long migration distance of this species to this area. Spot and Atlantic croaker from upriver oligohaline creeks exhibited lower mortality rates than fish from downstream polyhaline creeks. These results indicated that even though growth was similar at the ends of the estuaries, the upstream habitats provided conditions that may optimize fitness through improved survival

Age, Growth, and Mortality of the Banded Drum, Larimus fasciatus (Sciaenidae) in North Carolina

Age, growth, and mortality were examined for Larimus fasciatus collected off North Carolina from September 1975 through September 1976. Fish were aged using length-frequencies, scales, and to a lesser extent otoliths. Problems encountered with aging a rare, short lived, temperate fish were discussed. The maximum size observed was 182 mm SL, and 86% of the specimens were \u3c 128 mm SL. The oldest banded drum reached age 4. Mean weighted back-calculated sizes (scale data) for age classes 1·4 were 75.2 mm, 145.4 mm, 161.8 mm, and 170.8 mm, respectively. The von Bertalanffy growth equation was: Lt = 178 (1·e-0.98(t + 0.38)), which predicted sizes at ages 1-4 of 132 mm, 161 mm, 172 mm and 176 mm SL, respectively. Observed, back-calculated, and von Bertalanffy growth curves agreed closely and indicated the fastest growth was in young fish during the spring and summer. The von Bertalanffy growth coefficient (K = 0.98) suggested that maximum size was attained quickly. Instantaneous (Z) and total annual (A) mortality rates were 1.44 and 76%, respectively. Weight-length and total length-standard length conversions were derived

Observing Reef Fishes from Submersibles Off North Carolina

During August and September 1979, the submersibles JOHNSON SEA LINK-II and NEKTON GAMMA were used to observe fishes at 13 reefs in Raleigh, Onslow, and Long Bays, N.C., at depths ranging from 23 to 152m. Reefs with the highest profile (up to 10m) and in depths of 52 to 92 m exhibited the greatest fish species richness and abundance, while adjacent sandy areas were usually barren of fishes. Estimates of recreationally and commercially important reef fishes were 61/ha (S.E. 59.9) over sand and 774/ha (S.E. 748.1) over reefs, with considerable variation between stations. Ninety-nine species in 35 families were observed. Most numerous were Holocentridae, Serranidae, Priacanthidae, Haemulidae, Sparidae, Sciaenidae, Chaetodontidae, Pomacentridae, and Labridae. Many tropical species previously thought to be rare off North Carolina were abundant

Fish species associated with shipwreck and natural hard-bottom habitats from the middle to outer continental shelf of the Middle Atlantic Bight near Norfolk Canyon

Fish species of the Middle Atlantic Bight (MAB) continental shelf are well known; however, species occupying hard-bottom habitats, particularly on the outer shelf, are poorly documented. Reef-like habitats are relatively uncommon on the MAB shelf; therefore, shipwrecks may represent a significant habitat resource. During fall 2012 and spring 2013, 9 sites (depths: 42–126 m) near Norfolk Canyon were surveyed by using remotely operated vehicles. One site consisted of sand bottom, one consisted of predominantly natural hard bottom, and 7 sites included 8 large shipwrecks. Of 38 fish taxa identified, 33 occurred on hard bottom and 25 occurred on soft substrata. Fourteen fish taxa occurred almost exclusively on hard bottom, and 6 species were observed only on soft bottom. The most abundant taxa, especially on reef habitat, were the chain dogfish (Scyliorhinus retifer), a scorpionfish (Scorpaena sp.), the yellowfin bass (Anthias nicholsi), the red barbier (Baldwinella vivanus), the black sea bass (Centropristis striata), unidentified anthiine serranids, and the deepbody boarfish (Antigonia capros). Depth, location, and season did not significantly influence fish assemblages. Fish assemblages on natural and artificial hard-bottom habitat were similar but significantly different from soft-bottom assemblages. Deep-reef fishes of the southern MAB may be constrained by zoogeography, depth, and inadequate habitat— limitations that could increase their vulnerability

Frequency of sublethal injury in a deepwater ophiuroid, Ophiacantha bidentata, an important component of western Atlantic Lophelia reef communities

The occurrence and relative abundance of tissue (arm) regeneration in the ophiuroid, Ophiacantha bidentata (Retzius), was examined in individuals collected primarily among colonies of the deep-water coral Lophelia pertusa off the southeastern United States. Seven deep-water coral sites (384–756 m), located between Cape Lookout, NC, and Cape Canaveral, FL, were sampled in June 2004 using a manned submersible. The presence of regenerative tissue was evaluated by visual inspection of each individual ophiuroid, and the proportion of regenerating arms per individual was examined relative to size of individual, geographic location, and depth of collection. Ophiacantha bidentata, the dominant brittle star collected, commonly displayed signs of sublethal injury with over 60% of individuals displaying some evidence of regeneration. These levels of regeneration rival those reported for shallow-water ophiuroids. Larger individuals (\u3e6.5 mm disc size) had a higher incidence of regeneration than smaller individuals. Size of individual and percent of regeneration were negatively correlated with depth. Although O. bidentata was significantly less abundant in southern versus northern sites, ophiuroid abundance did not appear to be influenced by amount or density of coral substratum. Presence of dense aggregations of O. bidentata indicates that they are an important component of the invertebrate assemblage associated with deep-water coral habitat especially in the northern part of the study area. Assuming that observed frequencies of injury and subsequent regeneration represent predation events then dense ophiuroid aggregations in deepwater coral habitats represent an important renewable trophic resource within these communities

Anguilliform larvae collected off North Carolina

The distinctive larval stage of eels (leptocephalus) facilitates dispersal through prolonged life in the open ocean. Leptocephali are abundant and diverse off North Carolina, yet data on distributions and biology are lacking. The water column (from surface to 1,293 m) was sampled in or near the Gulf Stream off Cape Hatteras, Cape Lookout, and Cape Fear, North Carolina during summer through fall of 1999–2005, and leptocephali were collected by neuston net, plankton net, Tucker trawl, and dip net. Additional samples were collected nearly monthly from a transect across southern Onslow Bay, North Carolina (from surface to 91 m) from April 2000 to December 2001 by bongo and neuston nets, Methot frame trawl, and Tucker trawl. Overall, 584 tows were completed, and 224 of these yielded larval eels. The 1,295 eel leptocephali collected (combining all methods and areas) represented at least 63 species (nine families). Thirteen species were not known previously from the area. Dominant families for all areas were Congridae (44% of individuals, 11 species), Ophichthidae (30% of individuals, 27 species), and Muraenidae (22% of individuals, ten species). Nine taxa accounted for 70% of the overall leptocephalus catches (in order of decreasing abundance): Paraconger caudilimbatus (Poey), Gymnothorax ocellatus Agassiz complex, Ariosoma balearicum (Delaroche), Ophichthus gomesii (Castelnau), Callechelys muraena Jordan and Evermann, Letharchus aliculatus McCosker, Rhynchoconger flavus (Goode and Bean), Ophichthus cruentifer (Goode and Bean), Rhynchoconger gracilior (Ginsburg). The top three species represented 52% of the total eel larvae collected. Most leptocephali were collected at night (79%) and at depths \u3e 45 m. Eighty percent of the eels collected in discrete depth Tucker trawls at night ranged from mean depths of 59–353 m. A substantial number (38% of discrete depth sample total) of larval eels were also collected at the surface (neuston net) at night. Daytime leptocephalus distributions were less clear partly due to low catches and lower Tucker trawl sampling effort. While net avoidance may account for some of the low daytime catches, an alternative explanation is that many species of larval eels occur during the day at depths \u3e 350 m. Larvae of 21 taxa of typically shallow water eels were collected at depths \u3e 350 m, but additional discrete depth diel sampling is needed to resolve leptocephalus vertical distributions. The North Carolina adult eel fauna (estuary to at least 2,000 m) consists of 51 species, 41% of which were represented in these collections. Many species of leptocephali collected are not yet known to have juveniles or adults established in the South Atlantic Bight or north of Cape Hatteras. Despite Gulf Stream transport and a prolonged larval stage, many of these eel leptocephali may not contribute to their respective populations

Fishes associated with pelagic Sargassum and open water lacking Sargassum in the Gulf Stream off North Carolina

The community structure of fishes associated with pelagic Sargassum spp. and open water lacking Sargassum was examined during summer and fall cruises, 1999–2003, in the Gulf Stream off North Carolina. Significantly more individual fishes (n= 18,799), representing at least 80 species, were collected from samples containing Sargassum habitat, compared to 60 species (n=2706 individuals) collected from openwater habitat. The majority (96%) of fishes collected in both habitats were juveniles, and planehead filefish (Stephanolepis hispidus) dominated both habitats. Regardless of sampling time (day or night), Sargassum habitat yielded significantly higher numbers of individuals and species compared with open-water collections. Overall, fishes collected by neuston net tows from Sargassum habitat were significantly larger in length than fishes collected from open-water habitat with neuston nets. A significant positive, linear relationship existed between numbers of fishes and the quantity of Sargassum collected by neuston net. Underwater video recordings indicated a layered structure of fishes among and below the algae and that smaller fishes were more closely associated with the algae than larger fishes. Observations of schooling behaviors of filefishes (Monacanthidae), dolphinfish (Coryphaena hippurus), and jacks (Carangidae), and fish-jellyfish associations were also recorded with an underwater video camera. Our data indicate that Sargassum provides a substantial nursery habitat for many juvenile fishes off the U.S. southeast coast