Introduction
Rising global demand for scallops has led to the collapse of many wild fisheries, increasing the need for sustainable aquaculture. In New Zealand, farming of the native scallop Pecten novaezelandiae remains undeveloped, but its emergence will help to address the growing need to diversify the aquaculture industry. Previous farming trials on P. novaezelandiae indicated that while suspended culture was technically feasible, the low survival (~ 30%) over the course of the trials, meant it would not be economically viable (Cameron, 1983; Bull et al.,1989). However, these trials involved limited husbandry and did not incorporate key parameters, such as managed stocking densities and routine net cleaning to reduce biofouling, both of which are known to impact scallop performance. This study measured spat performance (growth of shell height and survival) during nursery culture with improved husbandry practices and compared scallop performance during grow-out across a range of net types.
Materials and Methods
Growth and survival of spat was measured during nursery culture. Performance of post-nursery scallops were then compared across three net types (pocket nets, mesh-base lantern nets and plastic-base lantern nets) during the grow-out phase.
Results and Discussion
Of the initial 3600 spat seeded, 89.5% survived the nursery phase (183 days), and 26.2% survived the grow out phase (216 days) resulting in 23.5% survival from seeding through to harvest (399 days). Spat grew from 13.5 mm to 39 mm shell height (SH) over the nursery culture period and then to 70 mm SH over the course of grow-out. In the grow-out phase, pocket nets achieved the highest survival (63.7%) and reached the largest size (79.5 mm SH), followed by mesh-base lantern nets (29.1%, 62.5 mm SH) and plastic-base lantern nets (14.8%, 68 mm SH).
This study confirms that with adequate husbandry practices, performance of P. novaezelandiae during nursery, can be improved to levels consistent with international pearl net culture (Widman & Rhodes, 1991). Future research should prioritize optimization of the grow-out stage, which is where lower levels of survival were observed. These results demonstrate that scallops are a potential candidate species to help diversify New Zealand's aquaculture sector. However, further refinement in methodology will be required to improve inefficiencies currently experienced during grow-out.
Acknowledgments
This research was supported by The University of Auckland and Envirostrat (Ocean Regeneration Aotearoa).
References
Bull, M. F. (1989). New Zealand Scallop Enhancement Project-Cost and Benefits. (Editors), Proc. Aust. Scallop Workshop, Hobart, Australia, pp. 154–154.
Cameron, M. I. (1983). A Preliminary Investigation of the Economic Viability of Scallop Farming in New Zealand. MAF Economics Division Discussion Paper., 15(83), 33–33.Widman, J. C., & Rhodes, E. W. (1991). Nursery culture of the bay scallop, Argopecten irradians irradians, in suspended mesh nets. Aquaculture, 99(3-4), 257-267.