The publication of EC regulations establishing procedures for organic aquaculture production, coupled with the increasing global demand for organic products did not immediately stimulate the growth of organic fish farming in southern Europe. Nevertheless, Marisland – Madeira Mariculture Lda. – based in Funchal on the island of Madeira, which manages the Calheta Mariculture Centre hatchery (CMC), decided to make the change, and faced a series of significant challenges in converting their marine fish hatchery to meet the requirements for organic production. This was described in a paper presented at Aquaculture Europe 2014, in San Sebastián, Spain last fall by Dr. Carlos A.P. Andrade, (from CMC) and his colleagues Bernardo Sumares and Carlos Batista from Marisland. Collectively they expressed the hope that other hatcheries would benefit from Marisland’s experiences.
Facilities and methodologies
In 2000, the CMC hatchery adopted mesocosm semi-intensive culture in which fish larvae are grown in large (40m3) tanks. The low larval density and high dilution of wastes require little water renewal and pumping. Live feed is produced within the system and is supplemented with cultured rotifers, Artemia and inert diets at different culture stages. At CMC the system has evolved to a high degree of automation and is considered to offer the most appropriate culture conditions for the rearing of larvae of different species such as, Pagrus pagrus, Diplodus sargus, and Pseudocaranx dentex. In this hatchery the culture of juvenile fish follows conventional/intensive production methodology.
Converting to organic
There was limited experience and little literature available regarding marine fish hatchery production following the issuing of EU Reg. 710/2007 describing the requirements for organic culture certification. Despite the semi-intensive culture methods already being used at the CMC hatchery, the conversion to organic production presented challenges for the different life-stages. A preliminary study identified several major bottlenecks during the adaptation process to organic production, namely:
- Photoperiod with maximum 16 hours light: EC regulations limit day-length to conform with animal welfare requirements.
- Use of oxygen limited to emergencies: to reduce energy input and bring fish stocking density to acceptable levels
- Microalgae production with organic fertilizers: synthetic nutrients may not be used.
- Live feed production and/or enrichment with microalgae produced with organic fertilizers, or other certified organic products.
Testing and results
Testing a selection of local agriculture waste products such as plant infusions and liquid sugar-cane waste (vinhace) provided the choice of a balanced nutrient media formulation for the production of the microalgae Nannochloropsis sp., Rhodomonas sp. and Isochrysis sp. with comparable results to the standard nutrient media, Nutribloom@ (Necton – Companhia Portuguesa de Culturas Marinhas, SA). A drastic reduction of live feeds and juvenile fish density was needed to cope with the restrictions on oxygen input.
Changing to batch culture at a maximum density of 350 individuals/ml was the most appropriate choice for rotifer production. Both rotifers and Artemia were enriched exclusively with microalgae, or combined with marine oils from sustainable sources. The daylight limitations apply to both larvae and juvenile fish, and in turn lead to lower daily rations and extended production periods.
Change at a cost
Organic production of juvenile fish is an alternative to simply intensifying larval rearing. For established hatcheries that use semi-intensive production techniques, changing to organic production is more likely to affect the methodologies used rather than requiring any changes to the design and engineering of the facility. However, the adoption of new products and procedures that will need to be tested, plus the extended rearing cycles, will be made at a cost that will require careful evaluation prior to beginning the change to organic production.