Length–weight relationships for five species of Chimaerids and two species of Rhinochimaerids to the west of Ireland

Abstract

Length–weight regressions for five chimaerid species, Chimaera monstrosa Linnaeus, 1758, Chimaera opalescens Luchetti, Iglesias & Sellos, 2011, Hydrolagus affinis de Brito Capello, 1868, Hydrolagus pallidus Hardy & Stehmann, 1990 and Hydrolagus mirabilis Collett, 1904, and two Rhinochimaerid species, Rhinochimaera atlantica Holt & Byrne, 1909 and Harriotta raleighana Goode & Beane, 1895, are calculated from data collected during a series of deepwater surveys conducted by the Irish Marine Institute from 2006 to 2009. This work was carried out on the continental slope to the west and northwest of Ireland and the northern slope of the Porcupine bank. Samples were measured fresh at the end of each haul. Due to the fragility of the tails of many of these species, length measurements for Chimaerids were made to the pre supra caudal fin, while for Rhinochimaerids they were made to the second dorsal fin. Lengths were measured to the nearest centimetre below and weights were recorded to the nearest gram. Outliers were removed from the dataset according to difference in fits (DFFITS) (Belsley et al., Regression diagnostics: Identifying influential data and sources of collinearity, John Wiley & Sons; 1980). b values for the Chimaeridae ranged from 2.915 to 3.075, while r2 values ranged from .981 to .995. b values for H. raleighana and R. atlantica were 2.764 and 3.505 and r2 values were .977 and .976 respectively.