Spawning of French grunts, Haemulon flavolineatum, in recirculating aquarium systems

Background Because the French grunt, Haemulon flavolineatum, is an ecologically important reef fish prized by both recreational anglers and public aquariums, the wild population requires limits on harvests. Yet, the environmental conditions conducive for French grunt spawning in aquarium settings is not well understood. Therefore, the goal of this study was to document the conditions leading to voluntary spawning and the number of eggs produced by French grunts without the use of hormones or artificial insemination. Methods We hypothesized and verified that it is possible for French grunts to spontaneously spawn in human care. Forty individuals were collected around the Florida Keys and haphazardly stocked in five recirculating seawater systems each containing two 250-L circular tanks. Over the course of 87 days, eggs were collected daily from each system and environmental parameters were monitored. Results Total daily number of eggs released ranged from 0 to 207,644 eggs. Of the observed environmental parameters, temperature and alkalinity had the greatest impact on number of eggs released. This study demonstrates that it is possible for French grunts to reproduce in captivity with little environmental manipulation, thus an ideal candidate to culture for the zoo/aquarium industry.

Variation in occurrence of the fish-parasitic cymothoid isopod, Anilocra haemuli, infecting French grunt (Haemulon flavolineatum) in the north-eastern Caribbean

Parasites constitute the majority of coral reef animal diversity and are believed to contribute significantly to host, community and trophic dynamics. Anilocra spp. are large conspicuous ectoparasitic isopods, making them ideal models for host–parasite studies. In the tropical western Atlantic and Caribbean, Anilocra haemuli infects the ecologically important French grunt (Haemulon flavolineatum). French grunt are trophic connectors between reef and seagrass environments, and how A. haemuli infection influences connectivity is unknown. As a first step in understanding the French grunt–A. haemuli association, we conducted reef surveys during three consecutive years to quantify the abundance and prevalence of infected fish on reef sites in the north-eastern Caribbean. We examined their correlations with fish population and aggregation size, and social affiliation. Annual infected fish abundance and prevalence per site ranged from 0–24 fish and 0–66%. Prevalence: (1) appeared autocorrelated within bays among years; (2) was inversely correlated with population and aggregation size, although the statistical significance varied; and (3) was greater for solitary than aggregating fish. Our study provides the most comprehensive dataset for prevalence of any Anilocra spp., and the necessary baseline data for future studies on Anilocra–host dynamics, and the effect of parasites on trophic and habitat connectivity.

Augmentation of French grunt diet description using combined visual and DNA-based analyses

Trophic linkages within a coral-reef ecosystem may be difficult to discern in fish species that reside on, but do not forage on, coral reefs. Furthermore, dietary analysis of fish can be difficult in situations where prey is thoroughly macerated, resulting in many visually unrecognisable food items. The present study examined whether the inclusion of a DNA-based method could improve the identification of prey consumed by French grunt, Haemulon flavolineatum, a reef fish that possesses pharyngeal teeth and forages on soft-bodied prey items. Visual analysis indicated that crustaceans were most abundant numerically (38.9%), followed by sipunculans (31.0%) and polychaete worms (5.2%), with a substantial number of unidentified prey (12.7%). For the subset of prey with both visual and molecular data, there was a marked reduction in the number of unidentified sipunculans (visual – 31.1%, combined – 4.4%), unidentified crustaceans (visual – 15.6%, combined – 6.7%), and unidentified taxa (visual – 11.1%, combined – 0.0%). Utilising results from both methodologies resulted in an increased number of prey placed at the family level (visual – 6, combined – 33) and species level (visual – 0, combined – 4). Although more costly than visual analysis alone, our study demonstrated the feasibility of DNA-based identification of visually unidentifiable prey in the stomach contents of fish.