To develop improved broodstock management strategies for commercial-scale production of almaco jack Seriola rivoliana, two sets of experiments were conducted. Studies aimed to address the following: 1) variability in egg viability and the connection to brood nutrition; 2) need for environmental manipulation protocols to optimize spawn performance and gamete quality. A total of 23 mature adult S. rivoliana were collected in the western Gulf of Mexico (GoM) approximately 144 km offshore (90 miles) in 60 meters (195 ft) of water. Fish (2.0-4.0 kg in body weight) were transported to Mote Aquaculture Research Park in Sarasota, Florida. Two broodstock populations were established and maintained in separate photo-thermally controlled, closed, indoor recirculating tank systems (28m3).
In the first experiment, a series of broodstock diet-shifts were performed. Differences in fatty acid profiles were assessed to determine which fatty acids in eggs can be predictably altered and which affect egg and larval quality. Each diet provided approximately the same amount of total fatty acids (144 mg g-1 dw), but differing levels of individual fatty acids. All experimental diets (fed at 3% tank biomass) included 30% squid and either 70% Atlantic mackerel (Scomber scombrus); thread herring (Opisthonema oglinum); or Spanish sardines (Sardinella aurita). Egg size, proximate composition, and fatty acid composition were measured for 23 spawns. Spawn performance metrics assessed for each spawn included total egg production, fertilization rate, hatch rate, and 3-day survival. Eggs from adults fed Atlantic mackerel had significantly lower levels of eicosapentaenoic acid (20:5, n-3; EPA), docosahexaenoic acid (22:6, n-3; DHA), arachidonic acid (ARA, 20:4n-6), and total fatty acids, than those fed Spanish sardine or threadfin herring. Mean three-day percent survival was significantly higher (p<0.001) in larvae hatched from broodstock fed thread herring (33.2 ± 1.26) and Spanish sardines (33.2 ± 1.38) when compared with those fed Atlantic mackerel (19.4 ± 1.16). In the second study, a total of 78 spawns were collected from broodstock populations subjected to a variety of photo-thermal regimes. The photoperiod (light/dark; L/D) ranged from 12 L/12 D to 9 L/15 D and temperature from 14-26°C. The total number of eggs collected from each spawn ranged from 30,000 - 1,012,000 eggs. Fertilization was recorded between 21 and 92% with hatch rates ranging from 62 - 89%. In summary, captive almaco jack sourced from the GoM are able to spawn at a wide range of photo-thermal conditions, although spawn quality is highly variable.