Diversification of marine species has emerged as a priority on the aquaculture agenda of many countries, due to its great industrial potential and as an alternative to overfishing. This diversification brings new challenges in candidate species, including European hake (Merluccius merluccius), whose decisive challenges are the reduction of the mass mortality observed around 25 days after hatching, the optimization of early feeding and larval management.
With the aim of advancing the study of early feeding in European hake, researchers from the Oceanographic Institute of Vigo (Manuel Nande and Montse Pérez) and the Singular Center for Marine Research of the University of Vigo (Pablo Presa and Damián Costas) carried out a collaborative project in which they designed and tested a workflow management system with live prey. To do this, they identified the type and size of prey preferred by hake larvae upon hatching, established the optimal prey density that maximized larval feeding, determined the influence of light intensity on the feeding activity of early larvae, evaluated the growth differences between batches of larvae fed with zooplankton as a nutritional supplement and, finally, tested the growth efficiency of a progressive feeding protocol, designed for larvae up to 30 days post-hatch (dph).
The researchers observed that the larvae began to eat at 6 dph, selecting prey based on its size, pigmentation and behavior, and that their activity was maximum in darkness and medium light intensity (600 lx). They also verified that the optimization of rearing with respect to the classic culture, which uses commercial prey, had an effect on early growth and survival up to 30 dph. In addition, they observed that diets based exclusively on rotifers implied low larval growth and the unviability of hake cultivation after 15 dph, while the inclusion of wild zooplankton in early diets doubled the growth of 30 dph larvae with respect to diets based on artemia. Thus, the adaptive diet for larvae up to 30 days old designed according to live prey size (MiACop), which uses the combination of copepods, rotifers and commercial artemia nauplii, resulted in a growth five times higher than that of the artemia or zooplankton diet. In light of these results, the researchers suspect that the massive cannibalism observed in this species from 25 dph onwards is related to the absence of an adequate prey size to combine with the semi-dry weaning diet.
The researchers conclude that the current workflow design for early feeding of European hake proves to be a useful step in ensuring a higher proportion of juveniles entering the weaning phase.
The work carried out is an example of cooperation between marine researchers from two Galician research centres because, despite having modest funding, it is successful due to the establishment of scientific synergies. This study had the financial support of the Ministry of Economy and Competitiveness through the LETSHAKE project (AGL2013 – 48468-R), co-financed by the European Regional Development Fund (ERDF), and with the financial support of the Competitive Research Units Consolidation Programme co-financed by ERDF (Operational Programme Galicia 2007-2013, Department of Culture, Education and University Planning of the Xunta de Galicia, RN AOE_2008-080) through the cooperation actions HAKEUP and HAKEU+.
Os resultados foron publicados en Aquaculture e estarán dispoñibles ata o 29 de xuño de 2017 na seguinte ligazón:
https://authors.elsevier.com/a/1V0u-ACeXvouB
