The effect of metabolic phenotype on sociability and social group size preference in a coral reef fish

Although individuals within social groups experience reduced predation risk and find food patches more consistently, there can be competition for food among groupmates. Individuals with a higher standard metabolic rate (SMR) may be less social, to prioritize food acquisition over defense, while a greater maximum metabolic rate (MMR) may modulate sociability through increased competitive ability. Therefore, in theory, individuals with a higher SMR may prefer smaller groups and those with greater MMR may prefer larger groups. We examined links among metabolic phenotype, sociability, and choice of group size in the redbelly yellowtail fusilier Caesio cuning. Individuals were exposed to three association tests: (a) a choice between two fish or zero fish; (b) a choice between five fish or zero fish; and (c) a choice between two fish and five fish. The first two tests quantified sociability while the third measured relative group size choice. Although there was no link between SMR and sociability, fish with a higher MMR were more social than those individuals with a lower MMR. While no correlation was found between MMR and group size choice, there was weak evidence that, if anything, individuals with a higher SMR preferred larger groups, contrary to our hypothesis. As C. cuning is an active fish that spends a large proportion of time operating above SMR, this result could suggest that the links between sociability and SMR may shift depending on a species’ routine behavior. Links between sociability and MMR may arise if competitive ability allows individuals to obtain resources within groups. Although metabolic traits had no significant influence on group size choice, variation in food availability or predation risk could alter the effects of metabolism on group size choice

Decadal trends of coral disease and benthic community structure in Dry Tortugas National Park

The coral reefs of the Florida Reef Tract have had the attention of scientists since the 19th century. In recent years, coral disease outbreaks have been more frequent, and subsequently these reefs have experienced phase shifts and large scale die-offs. Coral reef communities have been ranked as the number one vital sign by The South Florida and Caribbean Inventory and Monitoring Network of the National Park Service. Since 2008, the inventory and monitoring network has collected data annually recording the composition of coral reefs through standardized protocol. Throughout this time, benthic communities have faced many direct and indirect anthropogenic stressors including the increase in temperatures, nutrients, and overfishing. Recently, the Caribbean has emerged as a coral disease hotspot. Dry Tortugas National Park contains reefs with some of the highest coral cover in the Florida Reef Tract. These reefs have experienced an increased frequency in coral disease outbreaks. It is important to investigate how the biotic factors of these reefs have responded to disease, as well as recognize the trends of the abiotic factors of the reefs associate with outbreaks

The Effect Metabolic Rate on Choice of Group Size in a Gregarious Coral Reef Fish

Group living comes with a variety of tradeoffs associated with food acquisition and predator avoidance. Individuals in larger groups may experience less predation risk but greater intraspecific competition for food resources. In addition, individual animals within a species vary widely in metabolic requirements, such that some individuals must feed more than others. A possible outcome is that individuals with a higher metabolic rate might be less social, or prefer to associate with smaller groups of conspecifics as the costs of competition may outweigh the benefits of predator avoidance. We studied these issues in redbelly yellowtail fusilier, Caesio cuning, a gregarious coral reef fish. The metabolic rate of all individuals was estimated via intermittent flow respirometry. Fish were then tested for sociability in a rectangular arena, where they were given a choice between associating with groups of various sizes (2 fish versus 5 fish; 2 fish versus 0 fish; and 5 fish versus 0 fish). All fish were tested under all three experimental conditions. Trials were recorded and analysed using automated tracking software to determine the amount of time in proximity to each shoal size. Early analyses suggest that fish with a higher SMR prefer smaller groups, most likely due to a higher prioritisation of foraging and a reduction in competition. This effect may also interact within baseline sociability as opposed to preference for shoal of a particular size per se. These results provide insight into the costs and benefits of group behaviours and the mechanistic underpinnings of sociability and group formation