Addition of Vertical Enrichment Structures Does Not Improve Growth of Three Salmonid Species during Hatchery Rearing

Michael Barnes

doi:10.15436/2381-0750.18.1957

Abstract

Environmental enrichment is the placement of structure or other modifications in typically sterile hatchery rearing units.This study investigated the use of vertically-suspended aluminum rod arrays in covered circular tanks on the rearing performance of brown trout (Salmo trutta), Chinook salmon (Oncorhynchus tshawytscha), and Atlantic salmon (Salmo salar) in separate trials lasting 59, 78, and 125 days respectively. No significant differences were observed in gain, feed conversion ratio, individual fish total length, or individual fish weight between the enriched and unenriched treatments in any of the three trials.In addition, vertically-suspended structure had no significant effect on Atlantic salmon relative fin length. These experiments are the first to indicate no benefits during the rearing of salmonids using vertically-suspended enrichment.

Highlights

Environmental enrichment is the deliberate addition of materials or structures to otherwise sterile hatchery rearing units in order to potentially improve fish behavior, growth, and post stocking survival[1]
Control tanks were devoid of any in-tank environmental enrichment structures, while experimental tanks included vertically-suspended linear enrichment structures described by Kientz and Barnes[17]
Experiment 1 – brown trout There were no significant differences in total tank ending weight, weight gain, or feed conversion ratio between fish reared either with or without the vertically-suspended rod arrays (Table 1)

Summary

Introduction

Environmental enrichment is the deliberate addition of materials or structures to otherwise sterile hatchery rearing units in order to potentially improve fish behavior, growth, and post stocking survival[1]. Some enrichment techniques previously studied have consisted of woody or stony debris, plant or root material, plastic plants, or concrete blocks added to hatchery tanks[6-13]. Despite their potential benefits, these types of enrichment features may trap food and feces or harbor pathogens, increasing the risk of disease or interfering with self-cleaning in circular tanks[14,15]. The vertically-suspended rod arrays did not interfere with the self-cleaning nature of the tanks, and required no additional labor during normal hatchery rearing compared to unenriched tanks They were shown to improve the growth and feed conversion ratio of rainbow trout (Oncorhynchus mykiss)[16,17]

Objectives

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Conclusion