DOI: 10.5061/dryad.83bk3j9zj
title: Data from: Seasonality and relative abundance within an elasmobranch assemblage near a major biogeographic divide

description: Nearshore waters are utilized by elasmobranchs in various ways, including
 foraging, reproduction, and migration. Multiple elasmobranch species have
 been previously documented in the nearshore waters of North Carolina, USA,
 which has a biogeographic break at Cape Hatteras on the Atlantic coast.
 However, comprehensive understanding of the elasmobranch community in this
 region is still lacking. Monthly year-round trawling conducted along two
 ocean transects (near Cape Lookout and Masonboro Inlet in 5 to 18 m depth)
 in Onslow Bay, North Carolina provided the opportunity to examine the
 dynamics and seasonal patterns of this community using a multivariate
 approach, including permutational multivariate analysis of variance and
 nonparametric BIO-ENV analysis. From November 2004 to April 2008, 21,149
 elasmobranchs comprised of 20 species were caught, dominated by spiny
 dogfish (Squalus acanthias) and clearnose skate (Rostroraja eglanteria).
 All species exhibited seasonal variation in abundance, but several key
 species contributed the most to seasonal differences in species
 composition within each transect. Spiny dogfish was most abundant in the
 winter at both locations, comprised mainly of mature females. Although
 clearnose skate was caught in all seasons, the species was most abundant
 during the spring and fall. Atlantic sharpnose (Rhizoprionodon
 terraenovae) was one of the most abundant species in the summer, and two
 distinct size cohorts were documented. Temperature appeared to be the main
 abiotic factor driving the community assemblage. The extensive year-round
 sampling provided the ability to better understand the dramatic seasonal
 variation in species composition and highlights the relative abundance of
 several understudied elasmobranch species that may be of significant
 ecological importance. Our results underscore the importance of inner
 continental shelf waters as important elasmobranch habitat and
 provide baseline data to examine for future shifts in timing and
 community structure at the northern portion of the biogeographic break at
 Cape Hatteras.
description: For a complete description of this dataset, please refer to our
 publication in Plos One. Briefly, elasmobranchs were surveyed with a
 bottom trawl on a monthly basis between November 2004 and April 2008.
 Sampling was conducted during all months of the year, although certain
 months are missing during specific years due to funding limitations.
 Sampling was conducted along two transects that extended from 0.4 to 8 km
 from shore, one transect was just west of Cape Lookout, the second was
 north of Cape Fear off Masonboro Inlet. All elasmobranchs (sharks, skates
 and rays) were counted by species, and up to 30 individuals of each
 species was measured for length and sexed. This dataset consists of the
 raw catch data of elasmobranchs, including numbers by species, and lengths
 and sex of a subsample (no subsample if n &lt; 30 for a give haul and
 species). 
description: # Data from: Seasonality and relative abundance within an elasmobranch
 assemblage near a major biogeographic divide
 [https://doi.org/10.5061/dryad.83bk3j9zj](https://doi.org/10.5061/dryad.83bk3j9zj) This dataset consists of the raw bottom trawl catch data of elasmobranchs from the monthly survey (2004 - 2008) off North Carolina. This dataset is associated with the Plos One publication "Seasonality and relative abundance within an elasmobranch assemblage near a major biogeographic divide" (Roskar et al.). ## Description of the data and file structure The dataset is in .xlsx format. The columns in the file are described below. 'haul' - the code used to identify individual trawl hauls, which were sequentially numbered. This survey in North Carolina, U.S.A. included multiple gear types, but only the bottom trawl data are provided here. Because hauls from other gear types were not included here, haul numbers are not always continuous (e.g., they start at #108). 'location' - identifies the distance from shore (miles) where the haul was conducted, parallel to shore. 'transect' - identifies one of two transects where the haul occurred, cl (Cape Lookout) or ms (Masonboro Inlet) 'year' - year when the haul was conducted 'season' - what season the haul was conducted in, according the analysis used for the Plos One publication (Roskar et al.) ' month' - month when the haul was conducted 'day' - day of the month when haul was conducted 'time' - time (2400 clock) when haul began 'temp' - surface water temperature (C) 'Sal' - surface salinity (ppt) 'DO' - surface dissolved oxygen (mg/l) 'Dtemp' - water temperature near the bottom (C) 'Dsal' - water salinity near the bottom (ppt) 'DDO' - water dissolved oxygen near the bottom (mg/l) 'species' - common name of species 'number' - total number of a species captured in a given haul. Note, this number is repeated in successive rows when multiple individuals of a given species is collected in a haul. 'length' - individual fork length (elasmobranchs) or disc width (skates and rays) of a measured elasmobrach (mm) 'sex' - sex of a measured individual (m - male, f - female)