Development of Limpet aquaculture: Advances on settlement and early growth of Patella aspera Röding, 1798

The limpet Patella aspera is an endemic species to the Macaronesian Islands. Its high economic value and vulnerability to exploitation has triggered the interest in the development of its aquaculture. Significant progress has been made in recent years, with the establishment of artificial fertilization and larval production protocols. However, there are at least two major challenges that need to be addressed before a commercial production can be achieved: larval settlement and juvenile grow-out. The aim of this research was to study the effect of different algae substrates (Ulvella lens, Amphora sp., Entomoneis sp., Navicula salinicola and Nitzschia sp.) on P. aspera settlement and to test the effect of two diets on juvenile growth: a mono diet based on U. lens versus a mixed diet composed by U. lens and the diatoms Nitzschia sp. and Navicula salinicola. Results showed that U. lens was the most efficient settlement cue, given that 84.6% of the post-larvae obtained were found on this algae substrate. In the following trial, U. lens was selected as the base diet for the grow-out phase. The rearing system used ensured juvenile survival percentages above 80%. The regular supply of the diatom mixture, as a dietary supplement, significantly enhanced juvenile growth performance. After 220 days post fertilization, limpets that grew on the mixed diet (U. lens plus diatoms) presented an average shell length of 19.280 ± 5.296 mm. Additionally, developed gonads were observed in females with less than 8 months. This study presents the first record of P. aspera juvenile grow-out, born from artificial fertilization, which represents a major step toward the development of limpet aquaculture.