Investigation of the potential of liposome and microparticulate feeds to partially replace microalgae in the nursery rearing of green‐lipped mussels ( Perna canaliculus )

Abstract

The seeding of small juvenile green-lipped mussels (Perna canaliculus) onto coastal farms is associated with high losses. These losses can be reduced by seeding larger juveniles; however, the nursery culture of juveniles is unviable because of the high cost of producing live microalgal feeds. In this study, we compared the ability for two diets, a formulated microparticulate feed, MySpat and liposomes fabricated with mussel extract to replace live microalgae at different proportions for feeding small (1.9 mm shell length ±0.02 SE) green-lipped mussels. The experimental diets consisted of a mix of live Tisochrysis lutea, Diacronema lutheri and Chaetoceros muelleri that were replaced with increasing proportions of MySpat (25%, 50% and 75%), and liposomes (25% and 50%). There were no significant differences in mortality of mussels relative to the control (100% microalgae) among any of the diet treatments. However, mussel growth tended to decrease with increasing substitution of the microalgal component of the diets. The results from this study suggest that microparticulate and liposome formats provide a viable mode of food delivery to juvenile mussels, with improved formulation of these formats having the potential to lead to the substitution of live microalgal diets which make nursery culture unviable at present.

Potential for Concentrated Microalgae as Replacement Diets for Juvenile Green-Lipped Mussels, Perna canaliculus

“…In a spat of the mediterranean mussel, Mytilus galloprovincialis, feeding of 75,000 cells•ml −1 of live microalgae and 2.5% MySpat ® on a mussel live weight basis resulted in similar weight gain to the spat fed with 150,000 cells•ml −1 of pure live microalgae over a three-week experimental period [27]. In green-lipped mussel spat, a replacement of live microalgae with up to 50% fabricated liposomes or up to 75% MySpat ® diet did not compromise the survival of spat over 32 days [28]. However, these previous studies mostly determined the performance of replacement feeds by measuring the survival and growth of the shellfsh, rather than examining diferences in their fnal nutritional status.…”

“…For example, consistently high losses of greenlipped mussel spat have been reported in New Zealand within a few weeks after seeding of the spat onto coastal farms [3,46,47]. Replacing the costly production of live microalgae in spat nurseries by either full or partial substitution with more cost-efective replacement diets is therefore a pressing need [28,48]. Te results of the current study indicate that two commercially available diets, LPB and SD, can substitute live microalgae for feeding spat of the green-lipped mussel by up to 50% without signifcantly compromising the survival and nutritional condition of the spat.…”

“…Tis is consistent with previous studies that have reported increased mortality of spat following partial replacement of live microalgae with alternative diets. For example, there was no diference in the mortality of green-lipped mussel spat after being fed with formulated diets, MySpat ® , at 0, 25, 50, 67, 75, 90, and 100% replacement for 21 days (ranging from 27 to 52% mortality) [48] or fed with 25% and 50% of fabricated liposomes for 32 days (ranging from 18 to 20% mortality) [28]. In mediterranean mussel spat, no mortality was observed in a spat when they were fed with 16% of live microalgae and up to 4.8% MySpat ® on a mussel live weight basis [27].…”

Microencapsulated diets using thraustochytrids and macroalgae side streams for nursery rearing of Mytilus galloprovincialis spat

“…Slower growth rates could require longer rearing periods for the spat in nurseries to reach an adequate size for grow-out phases on rafts, although this cost could balance against the greater seed loss at sea because of storms and other adverse natural environmental conditions impacting smaller-sized spat (Skelton et al, 2021). In any case, our aim was to assess and compare the growth of spat fed with microencapsulated diets and commercial algal paste in small-sized M. galloprovincialis in lab conditions.…”

“…Sustainable mussel farming is driving an increased interest in offshore aquaculture, which can support a faster and healthier growth of farmed species (Barillé et al, 2020;Kirchhoff et al, 2011), and is considered to reduce nutrient loadings into coastal environments (e.g., Bristow et al, 2008;Vezzulli et al, 2008). However, expanding culture of M. galloprovincialis in offshore systems is hampered by the current dependence on wild-collected juveniles ("spat") on ropes or through harvesting from the shore (Azpeitia, Ortiz-Zarragoitia, et al, 2017;Fernández-Reiriz et al, 2016), making the production susceptible to annual fluctuations in spat supply because of unpredictable environmental conditions (Kamermans & Capelle, 2019;Skelton et al, 2021). Adverse environmental conditions (e.g., strong storms; Rasilla et al, 2018), especially offshore, can lead to substantial mussel losses (up to 54%, P. South et al, 2017, or even 95%, P. M. South et al, 2022), particularly in suspended rope cultures (Lachance et al, 2008), where high densities and secondary settlement can cause detachment of smaller individuals (Lauzon-Guay et al, 2005; P. South et al, 2017; P. M. South et al, 2022).…”