Length–weight relations for seven grenadier species (Actinopterygii: Gadiformes: Macrouridae) to the west of Ireland

Brendan O'Hea,Graham Johnston,Leonie Dransfeld,Jonathan White

doi:10.3750/aip2013.43.4.04

Abstract

Length–weight regressions for seven grenadier species: Coryphaenoides rupestris Gunnerus, 1765, Trachyrincus murrayi Günther, 1887, Coelorinchus caelorhincus (Risso, 1810), Nezumia aequalis (Günther, 1878), Coryphaenoides mediterraneus (Giglioli, 1893), Coelorinchus labiatus (Köhler, 1896), and Coryphaenoides guentheri (Vaillant, 1888) are calculated from data collected on a series of deepwater surveys conducted by the Irish Marine Institute from 2006 to 2009, on the continental slope to the west and northwest of Ireland and the northern slope of the Porcupine Bank. The regression calculated for roundnose grenadier, C. rupestris, is compared with other regressions calculated for the species from different areas of its north Atlantic range. The difficulties associated with measuring many grenadier species, due to the fragility of their tails, are discussed. A recommendation is made that pre-anal fin length should be accepted as the standard.

Highlights

Length–weight regressions for seven grenadier species: Coryphaenoides rupestris Gunnerus, 1765, Trachyrincus murrayi Günther, 1887, Coelorinchus caelorhincus (Risso, 1810), Nezumia aequalis (Günther, 1878), Coryphaenoides mediterraneus (Giglioli, 1893), Coelorinchus labiatus (Köhler, 1896), and Coryphaenoides guentheri (Vaillant, 1888) are calculated from data collected on a series of deepwater surveys conducted by the Irish Marine Institute from 2006 to 2009, on the continental slope to the west and northwest of Ireland and the northern slope of the Porcupine Bank
Where authors produced a number of work has tended to focus on roundnose grenadier, regressions we selected the one corresponding closest to Coryphaenoides rupestris Gunnerus, 1765, and roughhead our work
The front edge of the anus; Bergstad 1990, Kelly et The surveys concentrated on three areas of the continenal. 1997), and pre-anal fin length (PAFL; from the tip of the tal slope to the west of Scotland and Ireland, and the snout to the base of the first anal fin ray (Jørgensen 1996) northern slope of the Porcupine Bank (Fig. 2)

Summary

Coelorinchus labiatus

In total 91 835 grenadiers comprising ten species were intact tails. This was despite the fact that the fish brought caught over the time series. Length–weight relations were back to the laboratory were selected as having calculated for seven grenadier species (Table 1). For C. rupestris, an intact fish was defined tion PAFL to TL relations were calculated for the two as one where the tail terminated at a hair-like point. A comparison of ‘intact’ fish, illustrating the difficulty in measuring total length–weight relations of Coryphaenoides rupestris from length in grenadier species. In many of the number of fish with damage increases with increasing species studied the fragility of the tail was length, and unbroken tails are rarely found on larger fish.

Min Max

Coryphaenoides mediterraneus

TL PA PAF

Findings

Conclusion