The effects of dietary lipid on spawning performance and egg quality in black sea bass Centropristis striata

UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
Christopher D Bentley (Creator)
Institution
The University of North Carolina Wilmington (UNCW )
Web Site: http://library.uncw.edu/
Advisor
Wade Watanabe

Abstract: The objectives of this study were to determine the effects of dietary lipid on spawning performance and egg quality in black sea bass (BSB) (Centropristis striata). The study was conducted over two consecutive spawning seasons. During year one, adult broodstock (N=162) were held in 1.8-m dia. Controlled environment tanks in sea water (35 g/L) and were fed three different dietary treatments: two commercially-prepared diets each with 45% protein and two different lipid levels (12% and 20%), and a natural diet of frozen fish, Atlantic silversides Menidia menidia. Broodstock were fed to satiation 6d/week beginning 3 mos. Before the spawning season and were subjected to photothermal conditions that mimicked natural variation until the spawning season (Apr.-Jul. 2005) when constant temperature (mean = 20.2) and photoperiod (13 L:11 D) were maintained. Mature females (mean oocyte diameter (MOD) = 330 µm) were implanted with a lutenizing hormone releasing hormone analog (LHRHa) pellet at a nominal dose of 72 µm/kg body weight (BW) and then held with 5 running males for volitional spawning. Egg collectors were monitored daily, and non-viable (sinking) eggs and viable (floating) eggs were quantified. Buoyant eggs were transferred to 18-L incubators at 35 g/L and 19ºC where fertilization and hatching success were determined as indices of egg quality. A total of 6 induced spawning trials were conducted for fish fed a natural diet of silversides, 7 for fish fed a 20% lipid diet, and 6 for fed a 12% lipid diet. Spawning performance varied widely among individual females within each treatment; however, fish fed a diet of silversides (31.9% lipid) had a significantly (P < 0.05) higher fertilization success (22.4%) than the commercially prepared diets with 20% and 12% lipid (4.8 and 0.6%, respectively). The silverside diet treatment also produced significantly more yolk sac larvae (YSL) per female (21.8 x 103) than the 12% treatment (0.3 x 103). Hatching success of the fertilized eggs was similar in all diets (silverside diet: 51.3%; 20% lipid diet: 58.6%; and 12% lipid diet: 40.0%), but only two spans from the 12% lipid diet yielded viable yolk-sac larvae. Eggs from the silverside treatment contained a significantly greater proportion of n-3 series fatty acids with docosahexaenoic acid (DHA) (22:6n-3) as the largest fraction. The eggs from commercially prepared dietary treatments contained significantly more n-6 fatty acids. The proportions of egg n-3 and n-6 fatty acids were similar to those found in the diets and are likely associated with the higher fertilization success of fish fed a diet of silversides. During year two, broodstock were fed three different dietary treatments: frozen Atlantic silversides, and two commercially-prepared diets with 45% protein and two different lipid levels (18% and 23%). Spawning protocols were the same as for the previous season, with the following exception: mean nominal dose of LHRHa was 50 µg/kg BW. A total of 8 spawning trials was conducted for fish in each dietary treatment. No significant (P<0.05) differences were detected among dietary treatments for spawning performance or egg quality parameters. As in year 1, eggs from the silverside treatment contained significantly (P<0.05) more n-3 fatty acids than eggs from the commercially prepared dietary treatments and significantly (P<0.05) fewer n-6 fatty acids. Docosahxaenoic acid was the largest portion of fatty acids in eggs of all treatments, with eggs from the silverside treatment containing a significantly larger proportion. The results suggested that dietary lipid has pronounced effects on spawning performance, egg fatty acid composition, and egg quality in BSB. For fish fed the commercially prepared diets, a dietary lipid level of 12% was clearly inadequate for successful reproduction. The poor spawning performance from the fish fed the 12% lipid diet may have been related to higher levels of linoleic acid (18:2n-6) found in this diet. For fish fed silversides, spawning performance varied greatly between experiments, which may indicate a variation in the quality of this natural diet.

Additional Information

Publication
Thesis
A Thesis Submitted to the University of North Carolina at Wilmington in Partial Fulfillment of the Requirement for the Degree of Masters of Science
Language: English
Date: 2009
Keywords
Black sea bass--Spawning, Black sea bass--Nutrition--Research, Black sea bass--Research
Subjects
Black sea bass -- Spawning
Black sea bass -- Research
Black sea bass -- Nutrition -- Research