Short communication Growth and survival of California sea cucumbers (Parastichopus californicus) cultivated with sablefish (Anoplopoma fimbria) at an integrated multi-trophic aquaculture site L. Hannah a , C.M. Pearce a, ⁎, S.F. Cross b, c a Fisheries and Oceans Canada, Pacific Biological Station, Nanaimo, British Columbia V9T 6N7, Canada b University of Victoria, Department of Geography and Coastal Aquaculture Research & Training Network, Victoria, British Columbia V8P 5C2, Canada c SEA Vision Group Inc., Courtenay, British Columbia V9N 9N8, Canada abstract article info Article history: Received 19 May 2012 Received in revised form 9 April 2013 Accepted 15 April 2013 Available online 24 April 2013 Keywords: Sea cucumber Parastichopus californicus Sablefish Anoplopoma fimbria Integrated multi-trophic aquaculture In a 12-month field trial we examined the growth and survival of California sea cucumbers (Parastichopus californicus) in suspended culture underneath net pens of sablefish (Anoplopoma fimbria) at an experimental integrated multi-trophic aquaculture (IMTA) site. We tested the effects of sea cucumber size (small: 7–99 g and large: 100–565 g whole wet weight) and stocking density (12, 17, and 21 ind m -2 ) on growth and sur- vival in a completely-crossed experimental design. We also compared growth and survival of experimental animals cultured directly under the fish pens with control sea cucumbers grown ~250 m away from the farm. The ability of the sea cucumbers to reduce total organic carbon and total nitrogen from the sablefish faeces was also examined. Small experimental animals grew significantly faster than large experimental in- dividuals, the former increasing in whole wet weight by 27–56% over the 12 months and the latter decreas- ing by 10–33% over the same period. It was concluded that stocking densities of large animals were too high to produce net positive growth. Stocking density had a significant effect on growth of both size classes, lower densities producing higher growth rates, or less negative growth rates in the case of large animals. Small sea cucumbers suspended directly below the sablefish net pens grew significantly faster than control individuals grown ~250 m away from the farm, which had negative growth over the 12-month period. The small sea cucumbers cultured under the net pens had a high survival rate (mean: 99.5%) and their feeding reduced the total organic carbon and total nitrogen contents of the sablefish faeces by an average of 60.3% and 62.3%, respectively, demonstrating their potential as an important organic-reducing component in IMTA. Suspending sea cucumbers below fish net pens, as opposed to growing them on the seabed, makes their col- lection and monitoring easier and moves them away from potential seabed predators such as sea stars. This study demonstrated that P. californicus is well suited to utilise the heavy fraction of waste from a sablefish farm while providing an additional valuable harvestable product. Crown Copyright © 2013 Published by Elsevier B.V. All rights reserved. 1. Introduction There are growing concerns regarding the ability of the environ- ment to sustain the expansion of intensive marine-finfish aquaculture and the effects of inorganic and organic wastes produced at fish farms (Brooks and Mahnken, 2003; Folke and Kautsky, 1989; Mayor and Solan, 2011; Pillay, 2004; Wu, 1995). Integrated multi-trophic aqua- culture (IMTA) offers a natural means to utilise some of the waste material from finfish aquaculture as inputs into the production of lower-trophic-level crops of commercial value, increasing both the environmental and economical sustainability of the aquaculture operation by reducing waste output and increasing product diversity (Troell et al., 2009). A successful fully-integrated IMTA system closely mimics natural ecosystem function (Folke and Kautsky, 1992), utilising species at several trophic levels to consume different types of waste: dissolved nutrient fractions can be absorbed by macroalgae, fine particulates consumed by filter-feeding shellfish, and heavier particulates taken up by deposit feeders (Chopin et al., 2001). Commercial-scale IMTA is established on the Atlantic coast of Canada, where blue mussels (Mytilus edulis) and kelp (Saccharina latissima and Alaria esculenta) are grown adjacent to Atlantic salmon (Salmo salar) (Neori et al., 2007; Reid et al., 2009; Ridler et al., 2007). On the Pacific coast of Canada, the pre-commercial-scale testing of IMTA with sablefish (Anoplopoma fimbria) in co-culture with Pacific scallops [an unconfirmed hybrid between the Japanese scallop (Mizuhopecten yessoensis) and the weathervane scallop (Patinopecten caurinus)], kelp (S. latissima), and sea cucumbers (Parastichopus californicus) has recently begun at a site Aquaculture 406–407 (2013) 34–42 ⁎ Corresponding author at: Fisheries and Oceans Canada, Pacific Biological Station, 3190 Hammond Bay Road, Nanaimo, British Columbia V9T 6N7, Canada. Tel.: +1 250 756 3352; fax: +1 250 756 7053. E-mail address: Chris.Pearce@dfo-mpo.gc.ca (C.M. Pearce). 0044-8486/$ – see front matter. Crown Copyright © 2013 Published by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.aquaculture.2013.04.022 Contents lists available at SciVerse ScienceDirect Aquaculture journal homepage: www.elsevier.com/locate/aqua-online