Protective socking material for cultivated mussels: a potential non-disruptive deterrent to reduce losses to diving ducks

Abstract

Predation of cultivated mussels by diving ducks can threaten the viability of mussel farms. Conventional scaring tactics have had limited success at deterring ducks from feeding on cultivated mussels, because of rapid habituation and 24-h feeding cycles of some waterfowl species. We tested a socking material containing a biodegradable protective layer against predation by diving ducks on experimental blue mussel (Mytilus edulis) aquaculture sites in Prince Edward Island, Canada. We also assessed the effect of this new socking material on mussel growth and survival. Results showed that the protective socking has the potential to reduce losses to ducks, but did not perform well for all mussel seed sizes used by the industry. The protective layer also did not biodegrade fast enough, trapping a portion of mussels inside the sock, affecting growth and survival of these mussels. Improvements are needed to make this solution effective for all mussel sizes used by the industry and to make its production more cost effective.

Mortality of marine mussels Mytilus edulis and M. galloprovincialis: systematic literature review of risk factors and recommendations for future research

“…Although no effect was observed in the two studies on M. galloprovincialis (Lok et al, 2007; O'Connor, 2010), inconsistent results were reported for the effect of this trait on the mortality risk of M. edulis . Discrepancies may be explained by different study conditions: mussel size was sometimes studied in combination with hypoxic conditions (Altieri & Witman, 2006), in the context of new socking material to protect mussels from predation (Dionne et al, 2006) or in the context of exploration of massive mortalities of wild beds (Tsuchiya, 1983) or cultivated mussels (Tremblay et al, 1998). A study also explored the effect of the initial seed size, showing that small seed had a higher mortality risk than larger seed (Lauzon‐Guay et al, 2005).…”

Effects of off‐bottom shellfish aquaculture on winter habitat use by molluscivorous sea ducks

“…Many of them involved active deterring of birds, such as chasing by boat, firing blank shots, propane cannons, underwater playback systems and use of powerful laser lights (Ross and Furness, 2000;Ross et al, 2001;Thompson and Gillis, 2001). There are also passive deterrents such as protective netting or socking, which restrict bird's access to cultured mussels (Ross and Furness, 2000;Dionne et al, 2006). In contrast to these studies, birds did not deplete cultured bivalves in Malaspina Complex and there are no records indicating that sea ducks feed on natural or cultured oysters.…”

Relationships between off-bottom bivalve aquaculture and the Magellanic steamer duck Tachyeres pteneres in southern Chile

“…Several studies have shown that bivalve aquaculture structures (rafts and longlines) provide good conditions for recruiting and growing mussels, additionally offering refuge to invertebrate predators, which, in turn, provide higher densities of betterquality prey for sea ducks than otherwise available in intertidal areas (Dionne et al 2006, Žydelis et al 2009, Varennes et al 2013. In fact, shellfish aquaculture offers a rare example in which the introduction of an industry leads to positive effects on wildlife populations (Žydelis et al 2009).…”

“…Shellfish aquaculture in Chile, as in other regions of the world, occurs in the intertidal-subtidal shallow nearshore waters, which also tend to harbour the highest densities and diversity of marine birds (Connolly & Colwell 2005, Dionne et al 2006, Žydelis et al 2009). Amongst the marine birds, sea ducks are a group of birds that are particularly likely to interact with shellfish aquaculture, as they are inherently linked to the same areas where most shellfish aquaculture occurs.…”

“…Amongst the marine birds, sea ducks are a group of birds that are particularly likely to interact with shellfish aquaculture, as they are inherently linked to the same areas where most shellfish aquaculture occurs. Sea duck diets include a high proportion of bivalves and crustaceans and some small fish (Del Hoyo et al 1992), making them potential predators of farmed shellfish, which would consequently negatively affect the economic success of the farm. However, shellfish aquaculture may negatively affect shorebird populations through habitat transformation or exclusion, or by disturbances arising from farming activities and boat traffic (Caldow et al 2003, Smith & Shackley 2004, Connolly & Colwell 2005, Gallardi 2014).…”