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The potential of integrated open-water mussel (Mytilus planulatus) and Atlantic salmon (Salmo salar) culture in North West Bay, Tasmania

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Cheshuk, Brian(Brian William) (2001) The potential of integrated open-water mussel (Mytilus planulatus) and Atlantic salmon (Salmo salar) culture in North West Bay, Tasmania. PhD thesis, University of Tasmania.

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Abstract

Tasmanian blue mussels (Mytilus planulatus) were cultured at four sites in the vicinity
of an Atlantic salmon (Salmo salar) farm in North West Bay, Tasmania. The main
objective of the study was to evaluate the potential of integrating mussel and salmon
culture within a common multi-species marine farm. Filter-feeding bivalves cultured
near open fish cages might obtain additional food supplies directly from particulate
wastes (excess fish feed and faeces) and indirectly from enhanced phytoplankton
production stimulated by dissolved nutrient wastes. Potential benefits of such
integration include enhanced bivalve growth, increased productivity of a coastal marine
fish farm, and reduced fish farm waste loadings and their associated environmental
impacts.
Mussels were cultured for fourteen months, suspended from four longlines positioned
at increasing distances (70, 100, 500 and 1200 meters) from the Aquatas Pty. Ltd.
salmon farm in North West Bay. Mussels were monitored monthly for various
growth and biochemical parameters including shell length, whole live weight, meat
weights, total biomass, condition index, glycogen content, stable isotope ratios (δ13C
and δ15N), reproductive development and survival. Water quality and environmental
parameters at each longline site were monitored weekly over the same period.
The performance of mussels grown within the fish farm lease (70 m and 100 m from
the fish cages) was not appreciably different from that of mussels grown distant to the
farm. Mussels spawned twice with no differences in biomass production among sites
(P > 0.05). The final sample in May 1996 indicated no site differences for any
parameter except for shell length (P < 0.0001) and condition index (P < 0.01).
However, site differences were minor, with final mean shell lengths and condition
(dry meat weight/internal shell cavity capacity) being within 2.0 mm and 17%,
respectively.
Similar mussel growth was likely due to similarities in environmental parameters
among longline sites, most importantly food quantity and quality (POM, chlorophylla,
%POM). Growth of mussels cultured within the fish farm was not enhanced due to
several contributing factors: (a) solid waste loadings (feed particles and faeces) from
the farm were too diluted to significantly increase particulate food concentrations above
ambient levels; (b) phytoplankton production within the farm was not enhanced; (c)
mussels may have been cultured too distant to intercept settling particulate wastes
emanating from the fish cages; and (d) ambient seston concentrations were above, or
near, the pseudofaeces threshold concentration for most of the trial period. Therefore,
mussels cultured within the farm site were physiologically limited in securing a
significant quantity of additional food.
Increased bivalve growth through integration with open-water fish culture may only be
achievable in coastal areas where ambient food concentrations are below the
pseudofaeces threshold for extended periods, particulate fish farm wastes significantly
increase particulate food concentrations above ambient levels, and bivalves are cultured
in a suitable position to intercept these waste particles.

Item Type: Thesis (PhD)
Keywords: Mytilus planulatus, Atlantic salmon, Mussel culture
Copyright Holders: The Author
Additional Information:

Thesis (Ph.D)--University of Tasmania, 2001. Includes bibliographical references

Date Deposited: 25 Nov 2014 00:50
Last Modified: 11 Mar 2016 05:54
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