A 60-day feeding trial was conducted to assess the suitability of three red algae, Hynea spinella, Hynea musciformis and Gracilaria cornea, as potential feed for the culture of juvenile abalone, Haliotis tuberculata coccinea R. Seaweeds were reared in a biofiltration unit with fishpond waste water effluents. The three algal species were found to contain high protein contents which would be related to its production under the high nitrogen culture conditions of the biofilter system. Protein and carbohydrate contents were highest in H. musciformis and lowest in G. cornea. Survival rates of juvenile abalone were very good, regardless of the algae fed. Feed intake of H. spinella was highest, followed by H. musciformis. Growth rates of abalone were within the range obtained under commercial conditions, final shell length and weight being significantly highest in animals fed H. spinella and lowest in those fed G. cornea. Feeding G. cornea lead to the lowest growth performance due to the lowest feed intake, whereas feed conversion ratios were significantly highest for H. musciformis and protein efficiency ratios were higher for both H. spinella and G. cornea. This study suggested the good potential of any of the three red seaweeds testedsuccessfully produced by the biofilter system, their nutritional composition being similar to other macroalgae used as feed for abalone and matching the abalone protein and lipid requirements-hence promoting growth and survival. Nevertheless, the biofilter produced macroalgae H. spinella showed the highest dietary value for juvenile of H. tuberculata coccinea.

No abstract

Diplodus vulgaris is characterized by a rudimentary hermaphroditism, with a low proportion of protandrous sex reversal. Male : female ratio is slightly unbalanced in favour of females (1 : 1.17), although no significant difference of the relation 1 : 1 was found. Both sexes have similar size distributions, with females predominating in larger sizes; a low proportion of intersexual individuals are distributed among the middle sizes. A protracted winter spawning season has been identified from November to March, with a peak in spawning activity in December-January. Size of maturity for males and females is attained in the second year of life.

The abalone, Haliotis tuberculata coccinea has been considered in the Canary Islands as a potential candidate species for aquaculture to restock its natural ecosystem. Because the study and development of artificial culture techniques require as much information as possible on natural populations, 20 monthly H. tuberculata coccinea samples were collected in the island of Gran Canaria between June 2005 and May 2007. Reproductive biology was assessed by histological techniques, and von Bertalanffy growth parameters were also estimated. Ovarian morphology of H. tuberculata coccinea showed 6 sexual cell stages during the oogenetic process and a group synchronous ovarian development. Its reproductive cycle is characterized by an annual spawning period throughout the entire year, although the maximum reproductive activity of this population was observed between August and February. Batch fecundity ranged from 85,749 (shell length (SL), 39 mm)-691,456 (SL, 62 mm), and a significantly higher fecundity rate was observed in individuals with an SL larger than 55 mm, suggesting that, to optimize egg production, this is the minimum broodstock size to be used in hatcheries. With regard to the population structure, the overall maleto-female ratio was 1:1.02 and the data of the size class analysis did not show any tendency. The von Bertalanffy growth parameters estimated for females and males were 72.5 and 78.8 mm in SL of asymptotic length, and 0.43 year-1 and 0.37 year-1 of growth rate.