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Reanalysis of long‐term surveys on the ecology and biology of mud skate ( Rhinoraja taranetzi Dolganov, 1985) in the northwestern Pacific (1993–2002)
Author(s) -
Orlov A. M.,
Tokranov A. M.
Publication year - 2010
Publication title -
journal of applied ichthyology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.392
H-Index - 62
eISSN - 1439-0426
pISSN - 0175-8659
DOI - 10.1111/j.1439-0426.2010.01512.x
Subject(s) - skate , biology , peninsula , fishery , bathymetry , zoology , juvenile , oceanography , ecology , geology
Summary Based on data sampled in 1992–2002, the occurrence, spatial distribution, bathymetry, bottom temperatures preferences, size composition, feeding, and some features of reproductive biology of mud skate Rhinoraja taranetzi in the Pacific waters off the northern Kuril Islands and southeastern Kamchatka are considered. Throughout the year, the mud skate was most abundant in the central part of the study area, from the coast of Onekotan Island to the southern tip of Kamchatka peninsula. The proportion of this species in bottom trawl catches in different seasons has changed slightly. However, maximum catch occurred in September–December. In April–May mud skates occupied shallower depths (mean 230–270 m), moving deeper in the summer period (mean 340–390 m). In December–March the skate occurred at lower bottom temperatures (mean 0.8–1.6°C) whereas the rest of the year it inhabited warmer waters with mean bottom temperatures of 2.5–3.1°C. Throughout the year decreasing body weight with depth was observed, indicating that adult and juvenile mud skates inhabit different depths. Total length of mud skates in catches ranged from 17 to 70 cm with a mean of 51.71 cm. Relation between total length (TL, cm) and body weight (W, g) was: W = 0.0029TL 3.1614 ( r 2 = 0.978). Males were more abundant among small skates (<30 cm) only, whereas females predominated among larger skates (>30 cm) comprising about 70% in 60–70 cm length class. Female mud skates were longer and heavier than males (mean length 56.9 vs 51.2 cm and mean weight 1206 vs 807 g, respectively). This species is considered to be benthophagous, consuming mostly amphipods (34.9% by weight), polychaete worms (27.6%), decapod crustaceans (12.7%), and fishery discards (13.9%). Small skates (20–40 cm) fed mostly on amphipods (85.4%); medium‐sized (40–60 cm) ate amphipods (40.2%), polychaetes (29.1%) and decapods (19.3%); the largest individuals (>60 cm) consumed fishery offal (27.9%) and less amphipods (26.6%) and polychaetes (27.7%). Preliminary data on the maturation of the species in the western Bering Sea showed that males and females become mature at lengths above 61 cm TL.