Various symbiotic relationships build and maintain coral reefs. Mutualistic relationships provide the organisms involved with an increased chance of survival and reproduction which prove important for the health and function of reef communities. The increasing presence of macroalgae is an indication of declining reef health. In order to maintain the growth of certain species of macroalgae, Threespot damselfish, Stegastes planifrons, cultivate and maintain algae gardens. If there is an abundance of algae in the gardens of S. planifrons, there is a limited opportunity for coral recruitment and growth; this makes them an important species in the ecosystem. Damselfish are very territorial and will defend their gardens by chasing and biting intruders. This study tested whether there is a particular sized territory surrounding the garden that correlates to the size of the garden itself. Attacks by S. planifrons in the gardens toward a laser pointer allowed the determination of garden and territory area. The area of the garden, the point where the attacks ended and the total surrounding territory of the damselfish were measured using a measuring tape. A positive trend between area of garden and area of territory was found indicating that both increased correspondingly. The algae gardens and territorial behavior of S. planifrons can be indicative of the current phase shift from a coral reef to a coral depauperate ecosystem. More algal cover is indicative of decreased coral cover and coral recruitment success. By understanding ecological dynamics, protection of coral reefs from a degrading phase shift can be implemented.
Bicolor damselfish, Stegastes partitus, are well known for their aggressive nature. They are known to attack almost any species threatening their food, territory or spawn, often regardless of the size of the intruder. Studies show that three spot damselfish are even able to identify certain species based on the threat they present by displaying different aggressive behaviors. However, little is known on how, and if, these aggressive displays are species dependent in bicolors. The purpose of this study was to test for species dependent aggression in bicolor damselfish during reproductive season to determine if this behavior relates to increased egg protection during reproductive season. Four damselfish individuals were analyzed over the course of five weeks during one reproductive and one non-reproductive cycle using underwater video camcorders. S. partitus was shown to increase frequency of aggression toward egg threatening intruders while guarding eggs. Conversely, they were shown to decrease in frequency of aggression towards intruders threatening their food resources. Lastly, the frequency of intrusion for eggeating intruders was not shown to significantly increase while bicolor damselfish eggs were present.
This student research was retrieved from Physis: Journal of Marine Science XV (Spring 2014)19: 9-14 from CIEE Bonaire.
Among fish that lay their eggs on the ground (demersal) and have external fertilization (oviparous), typical parental care includes building a nest, then cleaning and guarding it as an investment in the fitness and survival of their offspring. Male Caribbean sergeant major damselfish, Abudefduf saxatilis, take on a darker coloration when they prepare a nest and engage in mating rituals, then guard and aerate their nest. Aggression of the guarding A. saxatilis could be linked to a number of factors. Nest size, size of the guarding fish is, or age of the nest may all affect nest guarding territoriality. Based on observational data collected in Bonaire in the Dutch Caribbean, there was no association between aggression (attack rate or average response distance) the guarding fish size (fork length), nest area, number of eggs, or age of the nest. Aggression was found to correlate with time of day, which may have been due to higher abundance of egg predators later in the day. Nest guarding aggression and parental care are complex behaviors that are largely species and context specific, making it difficult to make true predictions about aggressive behavior.
This student research was retrieved from Physis: Journal of Marine Science XVII (Spring 2015)19: 58-68 from CIEE Bonaire.
Exclusive Economic Zone (EEZ) map of St. Eustatius and Saba (GIS). Includes contiguous zone and territorial sea. Based on the United Nations Convention of the Law of the Sea (UNCLOS, 1982) an Exclusive Economic Zone is a maritime zone over which a state has sovereign rights for the exploration and use of marine resources. See this report for more info.