Despite suggestions to the contrary, getting Dover sole (Solea solea) to breed in captivity is indeed possible, says Dr. Robbert Blonk, a Dutch specialist in the species and a lead researcher at IMARES, Wageningen UR.
Blonk told Hatchery International that the chances of developing a lucrative Dover sole culture industry in the Netherlands increased markedly this year when he and his colleagues succeeded in selecting suitable conditions for breeding and farming the fish, and significantly extended their reproductive period.
Blonk, director of the team working on the sole program, said that earlier this year the group was able to create conditions in which first-generation sole originally bred in the hatchery, spawned outside the usual wild-spawning season of April and May. This was done by manipulating photo-period and water-temperature, beginning in December last year.
The photoperiod was altered gradually to simulate spring, and the water temperature was raised over time to 11°C, to match the temperature that triggers spawning. He termed this January batch of juveniles the “advanced” group because they were born in advance of the usual spawning period. The research team has plans for a “delayed” batch, to be produced after the normal season, for arrival in July.
They were also able to keep some of the females producing eggs (up to 20,000 /day) for no less than three months, ensuring a super-abundance of eggs for hatching and final growout.
The group got good larval – and juvenile – survival rates using Artemia, but had experienced difficulty in developing a good growout feed.
According to Blonk the IMARES team has been working with two collaborating fish farms with the intention of developing a viable sole culture industry in the region. The work has now shown that by selecting the right fish it’s possible to make the sole reach the preferred market size of 250g in about 18 months, half the normal time, and a major benefit for any sole farming development.
Blonk, who has been working on the project with the region’s Fry Marine company, emphasized that year-round production of juveniles is essential for a developing fish-farming industry and meeting the consumer’s needs for a consistent supply, including size and flesh quality.
– Quentin Dodd