World Aquaculture Magazine - September 2021

34 SEP TEMBER 2021 • WORLD AQUACULTURE • WWW.WA S .ORG facing health issues did not feed well, or at all, further worsening their condition. Fish were fed an alternating diet of squid, clams and shrimp four times daily (Fig. 6). The only harem that produced repeated, successful volitional spawns was the tank that contained one large assumed male and five smaller fish ranging from 10 to 15 inches. Following one initial month of daily continuous volitional spawning, the assumed male jumped out of the tank, leading to its mortality, and volitional spawning of fertile eggs ceased. A new male was added to the tank the next day and was found dead two weeks later, again by jumping from the tank. We observed behavior of the fish in the tank during this two-week period and determined a resident fish must have been attempting to assert dominance as the primary male over the newly added fish. One fish began displaying some dominant behavior, consisting of dorsal fin dancing, and the darkening of the snout and tail. Although this fish displayed characteristic reproductive male behavior, only infertile eggs were spawned for the next two months as photothermal manipulation continued. Fertile spawns resumed on 14 April 2020 and were produced intermittently until 8May 2020, when fertile spawns began to occur almost daily for the rest of the year. Nearly 6 million fertilized and 4 million unfertilized eggs were produced by this single harem over one year (Fig. 7). Mating/Sparring Sparring between males and assumed males was observed only once as jaw-locking. Further aggressive behavior led one of the males to jump from the tank and die. After months of conditioning, harem groups have had single individuals that display male coloration (light pink to white body, deep maroon mask and caudal pattern) in daily intervals during the mid to later afternoon before returning to standard coloration. The male that displays these mating colorations also displays a behavior that consists of a rapidly shaking wave of its dorsal spines while chasing assumed females in the tank. When mating occurs, the male will follow a female, press alongside her, and then both will rise to the surface and part in opposite directions after expelling gametes. Photothermal Manipulation All three broodstock tanks had chillers installed six months after broodfish arrived at the facility. Prior to chiller installation and upon introduction to the facility, the light- dark schedule for the entire building where broodfish tanks are housed was 12 h or light alternating with 12 h of darkness. One month prior to chiller installation, overhead lights were installed directly above all adult hogfish tanks. These lights were set for a period of 8 h of light and 16 h of darkness. Temperatures were not regulated prior to chiller installation and ranged from 26-29 C. Upon chiller installation, tanks were immediately dropped 3 C to attain a temperature of 23 C. Harems then underwent further 2 C and 30-min daylight changes independent of one another based on spawning performance. Groups experienced as much as an 8 C and 2-h photoperiod change to induce spawning. General Observations Fish were reclusive upon introduction to brood tanks and should be provided multiple shaded areas to hide including shade covers, overhangs, opaque tunnels and PVC pipes (Fig. 6). Once established and feeding, fish exhibit exploratory and grazing behavior. Fish have been observed to jump when startled when the tank wall was struck, sudden light changes and quick movements. It is recommended to securely cover tanks with nets, especially harems with males. Egg Collection and Larval Culture The day after the initial temperature drop, eggs were observed in the egg collector of a broodstock tank at 0800 h. Eggs were collected every morning at 0800 h and subsamples were quantified with a microscope to estimate the number of eggs spawned and fertilization percentage (Fig. 8). Eggs were stocked into 110-L tanks in the larval rearing room of the UF-IRREC-AL facility to research and define most effective larval culture protocols. The larval rearing room consisted of twelve 110-L tanks in a recirculating system. FIGURE 7. Volitional spawning of a brood hogfish harem and fertile and total egg production during eleven months of the study after undergoing photothermal manipulation. Spawned 303 To ta l Numbe r o f Mean Numbe r o f % o f To ta l o f 336 Day s Egg s Spawned Egg s Pe r Spawn Numbe r o f Egg s Fertilized 5,865,152 19,357 61.7 Unfertilized 3,634,313 11,994 38.3 The common name, which incorporates the term “snapper,” along with the high value of hogfish, has led to intentional mislabeling of lower-value seafood products as hogfish in foreign fish markets. Such a high-priced fish has the potential for large profits if economical aquaculture technologies can be demonstrated, which could also lead to a safer, properly labeled seafood product.