Age, growth, and morphology of larval redfish, Sebastes sp. (Pisces: scorpaenidae) on Flemish cap, 1980-1981

Penney, Randy W. (1984) Age, growth, and morphology of larval redfish, Sebastes sp. (Pisces: scorpaenidae) on Flemish cap, 1980-1981. Masters thesis, Memorial University of Newfoundland.

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Abstract

Larval redfish, Sebastes sp., were collected for growth analysis and morphological studies on Flemish Cap, an offshore bank approximately 400-500 kilometers east of the Island of Newfoundland, Canada, using paired Bongo nets. Several cruises were completed during 1980 and 1981. Increments, which are believed to form daily from date of extrusion, were counted from sagittae and measurements of sagittal radii were taken for back-calculation of individual growth histories. -- Mean daily growth rates and back-calculated growth histories of over 1200 redfish larvae were determined. Mean daily growth was 0.160 mm per day and 0.109 mm per day in 1980 and 1981 respectively. Total larval length was a linear function of age. A significant non-linear relationship between total length and sagittal, radius, and measurements of sagittal radii at intervals of 5 increments were used to back-calculate the length at extrusion and growth history of each larva. -- Growth rates varied considerably over the first 110 days of life. Larvae typically experienced an initial period of reduced growth for 10-15 days following extrusion followed by a sharp increase and a period of relatively fast growth for 60-70 days before declining as larvae entered the pelagic juvenile stage. Larvae extruded late in the season in 1980 tended to grow faster at all ages than larvae extruded early in the season. -- Because of continuing controversies regarding the identification of possibly three species of redfish: S. marinus, S. mentella, and S. fasciatus, a variety of morphometric, meristic, and pigmentation variables were measured and their utility as identification criteria evaluated. Principal Component Analysis could not identify morphometrically distinct groups which might be used to establish species identification criteria. Differences in morphometry, meristics and pigmentation patterns were closely associated with time of extrusion. Larvae extruded late in the season tended to be more robust and thicker-bodied and developed ossified skeletal elements at relatively smaller sizes compared to earlier extruded larvae. -- The observed morphological differences might be attributable to environmental influences rather than to the presence of larvae of more than one redfish species. The morphological and growth rate differences between larvae extruded at different times have important ecological implications. Due to their relatively earlier ossification of fin rays and supports, coupled with larger head size, broader gape, and larger gut areas, the later extruded larvae are probably more active predators, capable of capture and ingestion of larger prey which are, energetically, more advantageous for larval growth and survival.

Item Type: Thesis (Masters)
URI: http://research.library.mun.ca/id/eprint/7885
Item ID: 7885
Additional Information: Bibliography: leaves 159-166.
Department(s): Science, Faculty of > Biology
Date: 1984
Date Type: Submission
Geographic Location: Atlantic Ocean--Flemish Cap
Library of Congress Subject Heading: Sebastes marinus--Flemish Cap

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