Date of Award

Winter 2009

Project Type

Thesis

Program or Major

Zoology

Degree Name

Master of Science

First Advisor

David Berlinsky

Abstract

Fishmeal is the main ingredient in formulated fish feeds, and the cost of this commodity is the largest and most volatile recurrent expenditure by the finfish aquaculture industry. Additionally, the reliance on wild-harvested forage species raises concerns about the industry's ecological impacts. Marine macroalgae and soy-derived feed ingredients both have merits as alternative proteins for piscivorous marine fish. Atlantic cod, in particular, have a highly adaptable digestive system and perform well with alternative protein diets.

Atlantic cod, Gadus morhua, juveniles (initial body weights: 15.6 g, 87.9 g, and 15.92 g) were fed iso-nitrogenous, iso-caloric diets to evaluate two alternative proteins. In the first experiment, purple laver (Porphyra spp.) replaced 0%, 15%, or 30% of the fishmeal in a commercially available marine finfish diet. In the second experiment, diets contained soy protein concentrate (SPC) to provide 0%, 10%, 20%, 30% or 40% dietary soy protein or to replace 0%, 25%, and 50% of the fishmeal in a commercially available diet for marine finfish. No differences in survival, growth, or hepatic-somatic indices were found among any of the treatment groups. The fish attained an average weight of 41.0 g with a specific growth rate (SGR) of 1.19% and a feed conversion ratio (FCR) of 1.26 in the first experiment. In the second experiment, the fish attained average weights of 162.7 g in the first trial and 39.1 g in the second trial with SGRs of 0.76% and 1.12% and FCRs of 1.28 and 1.29, respectively. These results indicate that soy protein concentrate can entirely replace fish meal in diets for juvenile Atlantic cod. Additionally, SPC or Porphyra can be combined with other common feed ingredients to replace dietary fishmeal by at least 50% or 30%, respectively.

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