Shawn M. C. Robinson

Social aspects of the sustainability of integrated multi-trophic aquaculture

A pilot project in the Bay of Fundy, Canada, is growing kelps, mussels, and salmon in an integrated multi-trophic aquaculture (IMTA) system. Biological and economic results are positive, but social acceptability is also a critical component of aquaculture sustainability. Focus group sessions with several segments of the population (restaurateurs, residents of communities near aquaculture facilities, and the general population) were held and the participants’ knowledge of, and opinions on, IMTA were recorded. Most participants felt that IMTA had the potential to reduce the environmental impacts of salmon farming, benefit community economies, and improve industry competitiveness and sustainability. All felt that seafood produced in IMTA systems would be safe to eat and 50% of the participants were willing to pay 10% more for these products if labelled as such. The participants felt that IMTA appears to be an improvement over current monoculture practices and would be cautiously welcomed in the marketplace. A promotional campaign educating the general public, food distributors, and other industry stakeholders about the positive benefits of IMTA would go a long way in gaining mainstream acceptance of this aquaculture practice.

A Review of the Northern Sea Cucumber Cucumaria frondosa (Gunnerus, 1767) as a Potential Aquaculture Species

Sea cucumbers are highly marketable as a food and medicinal product. Many species are being cultured in addition to being fished to meet the high demand for these products. This review explores the potential use of the Northern sea cucumber, Cucumaria frondosa, as a viable aquaculture species in the North Atlantic. Utilizing the literature available on this species, the marketability, biology, production cost, hatchery potential, grow-out technology, and alternate uses within integrated multi-trophic aquaculture sites were examined. C. frondosa is well suited for culture in that it has an established market, it is abundant, its reproductive biology is well understood, and it has potential as an extractive co-culture species. Its slow growth rate and low value could limit its production.

Enhanced Growth Rates and Condition Index of Blue Mussels (Mytilus edulis) Held at Integrated Multitrophic Aquaculture Sites in the Bay of Fundy

ABSTRACT Atlantic salmon (Salmo salar) farms in the Southwest Bay of Fundy area of New Brunswick were investigated for possible advantages of nutritional enrichment for the blue mussel (Mytilus edulis) when grown in integrated multitrophic aquaculture (IMTA) systems. Mussels grown in IMTA systems may be exposed to higher concentrations of organic matter at the salmon farms that can enhance growth rates and decrease time to market for the grower. In this experiment, mussels were sock-cultured at 2 distances from 2 separate salmon farms (0 m and 200 m), with 3 growth parameters (shell length, wet meat weight, and condition index) measured monthly and compared with the same growth parameters in mussels grown at a reference site outside the aquaculture influence. After a12-mo period, mussels grown directly on the cages grew faster than mussels 200 m away on all parameters except shell length at 1 location. Mussels grown at 0 m and 200 m performed significantly better (P < 0.05) in all growth parameters compared with mussels grown at a reference site outside the aquaculture influence. Differences in growth and condition index were most pronounced in the fall and winter, when ambient seston concentrations were low. Results of a second study in which growth rates for individually tagged mussels was monitored for a 6-mo period confirmed that there is a significant growth benefit for mussels in integrated aquaculture with salmon compared with mussels grown 500 m away at a reference site.

DIETARY PROPORTION OF FISH CULTURE SOLIDS REQUIRED BY SHELLFISH TO REDUCE THE NET ORGANIC LOAD IN OPEN-WATER INTEGRATED MULTI-TROPHIC AQUACULTURE: A SCOPING EXERCISE WITH COCULTURED ATLANTIC SALMON (SALMO SALAR) AND BLUE MUSSEL (MYTILUS EDULIS)

ABSTRACT Integrated multi-trophic aquaculture (IMTA) aims to recapture portions of nutrient waste lost from 1 species as nutritional inputs for another. This process has the potential to augment growth of cocultured species while reducing the nutrient load from an aquaculture site. In several jurisdictions, open-water aquaculture is regulated through measures of benthic hydrogen sulfide concentrations, which is proportional to excess deposition of organic material such as feces and uneaten food. Interception, consumption, and digestion of organic portions from the fed trophic level (e.g., fish) by organic extractive species (e.g., shellfish, deposit feeders) results in “organic stripping,” with less organic material in resulting feces, thereby reducing the net organic load and benthic deposition potential. Shellfish are deployed beside fish cages in some openwater IMTA systems. In addition to the potential consumption of fish culture solids (i.e., feces, feed “fines”), natural particles (i.e., seston) will also be consumed. Consumption of seston portions by shellfish means that some suspended solids that would otherwise drift by fish cages now have the potential for redirection to the benthos as indigestible seston components, egested in shellfish feces. This raises the issue as to what dietary proportion of fish culture solids, consumed by extractive species, results in an increase or reduction of net organic load. As a scoping exercise, a simple mathematical model was created using known absorption efficiencies (fraction of organic material digested) of blue mussels (Mytilus edulis) on diets of seston, and Atlantic salmon (Salmo salar) culture solids, to estimate the resulting organic fecal load of blue mussels on a mixed diet. The organic load from the mussel feces was added to the unconsumed load of salmon culture organics to determine the net IMTA organic load. The dietary proportion threshold (DPT) is the percentage of fish culture solids in an extractive species diet that results in no change in net organic load at an IMTA site. The DPT of salmon culture solids that must be exceeded for mussel culture to reduce the net IMTA site organic load is 14.5% for salmon feces and high-quality seston, 19.6% for salmon feces and lowquality seston, 11.5% for salmon feed fines and high-quality seston, and 15.6% for salmon feed fines and low-quality seston. A net reduction of organic load occurs if the amount of salmon culture organics absorbed (digested) by mussels exceeds the organic fecal load produced by indigestible seston components. Changes in total particulate matter consumed by a mussel population or changes in the amount of salmon culture solids available did not change the DPT, although these factors did influence the magnitude of net organic load increases or decreases. Whether DPTs are achievable is a function of many biophysical parameters, and these avenues are not pursued in this study. However, knowledge of DPTs can be useful to frame expectations of nutrient mitigation and to assist in the interpretation of augmented growth and tracer data as a means to infer nutrient reduction potential.

The Canadian Integrated Multi-Trophic Aquaculture Network (CIMTAN)—A Network for a New Era of Ecosystem Responsible Aquaculture

ABSTRACT The Canadian Integrated Multi-Trophic Aquaculture Network (CIMTAN) is a Natural Sciences and Engineering Research Council strategic network that was initiated in 2010. It was triggered by the fact that aquaculture, though the world fastest growing food production sector, is associated with environmental, economic, and societal issues. Integrated multi-trophic aquaculture (IMTA) offers an innovative solution for the environmental sustainability, economic stability, and societal acceptability of aquaculture by taking an ecosystem-based management approach. IMTA is the farming, in proximity, of aquaculture species from different trophic levels, and with complementary ecosystem functions, so that one species’ excess nutrients are recaptured by the other crops and synergistic interactions among species occur. CIMTAN is providing the interdisciplinary research and development and highly qualified personnel training in the following linked areas: (1) ecological design, ecosystem interactions, and biomit...

Quantifying the Effects of Diet and Mussel Size on the Biophysical Properties of the Blue Mussel, Mytilus spp., Feces Egested Under Simulated Imta Conditions

ABSTRACT Three size classes of mussels (Mytilus spp.) (small, 26–35 mm; medium, 45–54 mm; and large, 65–74 mm) were exposed to 4 experimental diets consisting of mixed algae, diatom pastes, salmon feed “fines,” or salmon feces. Salmon culture byproduct particles (feces and feed fines) were found to have minimal effect on the biophysical properties of mussel feces when compared with those from an algal-based diet. Differences in fecal morphology (feces widths) of mussel feces were found to be minimal in small mussel sizes, but became more significant as mussel shell length increased (45–74 mm). Furthermore, faeces from fish farm-based diets were found to be significantly narrower than algal based diets. Absorption efficiencies of the 4 different diets were 87%, 81%, 90%, and 86%, respectively. Regardless of diet, small mussels produced feces that dispersed as a function of settling velocity (small, 0.18 cm/sec; medium, 0.29 cm/sec; and large, 0.54 cm/sec (settling velocity of 50% of particles)) over much larger areas than those feces produced by larger mussels, suggesting that the influence of mussel culture on benthic loading of organic material around an aquaculture site will tend to increase over time as the mussel crop grows to maturity.

Does Method of Kelp (Saccharina latissima) Storage Affect Its Food Value for Promoting Somatic Growth of Juvenile Green Sea Urchins (Strongylocentrotus droebachiensis)

ABSTRACT Harvested for their gonads, sea urchin populations are declining worldwide primarily as a result of overfishing. Consequently, research is now focusing on full life cycle aquaculture of these organisms. If juvenile or adult sea urchins are to be fed macroalgae (a preferred food of echinoids) in commercial-scale operations, suitable methods for storing large amounts of algae will be required. In this study, the effect of various storage methods for the kelp Saccharina latissima on somatic growth of juvenile green sea urchins, Strongylocentrotus droebachiensis, was evaluated. Juvenile S. droebachiensis (initial test diameter, 4.5–10.7 mm) were held in laboratory tanks, supplied with flow-through seawater, and fed ad libitum one of the following S. latissima treatments: (1) frozen long term (>2 mo), (2) frozen short term (1 wk), (3) air-dried, or (4) fresh. Measurements of test diameter and whole wet weight of the sea urchins were taken monthly for 16 mo. Mean (±SE) final sizes in the treatments ranged between 17.7 ± 0.4 mm and 21.7 ± 0.4 mm for test diameter and between 2.9 ± 0.2 g and 4.9 ± 0.2 g for wet weight (sea urchins fed long-term frozen kelp and air-dried kelp, respectively). There were no significant differences in growth rate—for either test diameter or wet weight—among sea urchins fed short-term frozen, air-dried, or fresh kelp, but those individuals fed long-term frozen kelp grew significantly slower than those on any of the other 3 diets. It is unclear, however, whether this difference is the result of the long-term freezing process per se or the result of differences in the biochemical nature of the kelp plants when they were collected for freezing. Because air drying should be relatively cheaper than freezing (in terms of energy cost), and air-dried kelp may be more easily stored and transported than frozen or fresh kelp, air drying is an obvious choice for long-term storage of kelp if it is to be used as a food for juvenile green sea urchins.

Evaluating the Use of Exhalent Siphon Area in Estimating Feeding Activity of Blue Mussels, Mytilus edulis.

ABSTRACT We evaluated the technique of measuring the exhalant siphon area (ESA) as an indicator of feeding activity in the blue mussel, Mytilus edulis. To accomplish this, we established the relationships between ESA measured using video and image analysis and clearance rate (CR) measured simultaneously in mussels exposed to various concentrations of microalgae as a food source in the laboratory. Two size classes of mussels (30 and 60 mm shell length) were fed 6 and 7 concentrations of the unicellular alga Isochrysis galbana., respectively (0, 0.6, 1.2, 1.8, 2.4, 3.0, 6.0 mg L-1). ESA and the variation in feeding activity associated with individual mussels significantly influenced CR in 60mm mussels, whereas effects of algal concentration were not significant within the range tested. Individual variation in feeding activity significantly influenced CR in 30 mm mussels. However, unlike the 60 mm mussels, ESA did not significantly influence CR, whereas algal concentration did have a significant effect in 30 mm mussels. We did observe significant relationships between ESA and CR in some groups of mussels suggesting it may be a useful indicator of feeding activity under certain circumstances. However, the high degree of variation observed in our laboratory-based experiments on the relationship between CR and ESA leads us to conclude that measurements of ESA may be better used as an estimate of general behavior trends in feeding rather than a quantitative measure of clearance rate.

A contingent valuation of the biomitigation benefits of integrated multi-trophic aquaculture in Canada

ABSTRACT Integrated multi-trophic aquaculture (IMTA) is the farming, in proximity, of aquaculture species from different trophic levels and with complementary ecosystem functions. IMTA allows one species’ uneaten feed and wastes, nutrients, and by-products to be recaptured and converted into fertilizer, feed, and energy for the other crops. By taking advantage of synergistic interactions between species, IMTA can help aquaculture evolve towards more responsible and sustainable systems. This study uses data from a contingent valuation survey to provide an estimation of the non-use benefits that, in the form of biomitigation of the external costs imposed on the marine environment, would be derived by Canadians from the adoption of IMTA for Atlantic salmon aquaculture. We find the benefits accruing to households who do not purchase salmon habitually would range between about

Chapter 16 Sea scallop aquaculture in the northwest atlantic

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