research projects | biodiversity | meiobenthos | coral ecology | fish ecology | fossil reefs | behavior
     
 
 

Increase of individual Prey Capture Rate based on Cooperation between the Peppered Moray (Muraenidae) and the Lyretail Grouper (Serranidae) in the Gulf of Aqaba/Red Sea - Diplomarbeit - Victoria von Mach

Abstract

The study deals with cooperation between members of different species in order to increase their individual capture rate. In the last years cooperation on an interspecific level reached attention relating to overcome the problems of intraspecific coordinated hunting. The adoption of different roles during a joint hunt which facilitate a successful association is a lot easier for individuals of different species. The study examines the association of the peppered moray (Gymnothorax griseus) and the lyretail grouper (Variola louti) in the Gulf of Aqaba. It is a comparison to Bsharys et al. (2006) investigations of the giant moray (G. javanicus) and the coral grouper (Plectropomus pessuliferus). The survey reveals that the species act in the same highly coordinated manner including communication like giant moray and coral grouper. The species stayed three times longer in contact than expected and during these contacts four signals of the lyretail grouper with different meanings could be recorded. Furthermore, groupers have a higher capture rate in cooperation with a moray (4.08 h-1) compared to hunting solitary (1.78 h-1). There are also impressive indications that these nocturnal morays benefit in the same manner from these associations. The willingness for cooperation increases with both proceeding daytime and ascending hunger level. Since the prey of the two predators is too small to be divided, monopolization of the carcass and rivalry can´t emerges. In addition indication that cooperation depends on groupers size is given in this study and so it seems that these coordinated hunts are about a learned behavior. The study documents for the first time that V. louti communicates additionally with octopuses in the same way like with moray eels. Participating species associate the presence of the other with a higher capture rate and thus optimize their individual hunting strategies.

 

Variola louti

Gymnothorax griseus

G.griseus & E.fasciatus

 
 

Aggression behaviour of Amphiprion bicinctus (the Red Sea Anemone fish) against anemone predators and its reaction on enemy schemes

Miriam Reininger - Magistra der Naturwissenschaften - January 2006 - Leopold-Franzens-University Innsbruck

In 1868 the symbiotic relationship between anemones and anemone fish was described for the first time. Since then scientists investigated many different fields concerning the symbiosis, the social organization of anemone fish, sexual stunts and the immunity to the nematocysts of the host anemones. In the last more than 170 years of investigation, research has led to a lot of contradictory results. This thesis deals with the aggression behaviour of Amphiprion bicinctus (the Red Sea Anemone fish) against predators and its reaction on enemy schemes.
A. bicinctus belongs to the Pomacentridae (Reef Perch) and is endemic in the investigated area where it is at the same time the only species of anemone fish found. Their natural distribution range includes the Red Sea and the Gulf of Aden. Anemone fish are unique among Reef Perch because they live in lifelong partnerships. Their small territory is probably the reason for this faithfulness. The host anemone is in the centre of the territory in which the fish reproduce, hide and search for food. All the species of anemone fish are obligate symbiosis-partners of sea anemones. One benefit of the symbiosis to the fish is obvious: its major source of protection is its anemone, which forms the core of its territory. The symbiosis is commonly regarded as facultative for anemones. However, anemone fish also provide protection against predatory fish to their hosts.
Innumerable theories about how the anemone/fish-partnership works have been elaborated. Behaviour and biochemistry, probably both, play roles to varying degrees. In fish that live with many types of host behaviour is likely to be more important to adaptation, whereas for host-specific fish biochemistry is probably
the more significant factor. Facultatively symbiotic Pomacentridae of the genus Dascyllus may occupy hosts instead of or along with true anemone fish. In some host anemones shrimps and crabs live together with anemone fish. Juvenile Labridae (Wrasse), Bleniidae (Blenny), Anthiidae (Fairy basslet) and Apogonidae (Cardinal fish) sometimes seek refuge near the tentacles of the anemone. They are not considered as true anemone fish, because the symbiotic relation is facultatively.
A. bicinctus lives in relatively large social units, often consisting of an adult pair and a series of juvenile sub-adults. Size-related dominance hierarchy exists in anemone fish. The larger female controls the production of other females by aggressive dominance. Like in other species of marine fish with closed social systems a subdominant individual can be induced to change sex by removal of the dominant one. This phenomenon has been described as socially controlled sex reversal. Sex change is relatively commonplace among fish, a remarkable adaptation that helps prevent any lull in reproduction, but it typically involves a female-to-male switch. The unusual male-to-female reversal in anemone fish is known as protandrous hermaphroditism. My field studies took place from July to September 2005 at the Red Sea Environmental Centre in Dahab, in the Gulf of Aqaba. In total I did 80 dives with more than 83 hours of underwater-observations. In the first half of my stay I registered the exact sites of the anemone/fish-partnerships and the parameters of the surrounding area to (e. g. depth, fish and anemone size, number of anemone fish living in the anemones, etc.) to investigate their influence on the behaviour of A. bicinctus.
After drawing up a behavioural catalogue I started my observations in twenty minutes intervals at four different depths. In the second half of my studies I carried our fake-experiments on A. bicinctus to see which contours evoke more or less aggression to replenish my observation studies. I also prepared three white-coloured replicas to see how big the influence of the natural colours on the aggression behaviour is. It was obvious that the colour is an important trigger of aggression behaviour. In the beginning of my field research I checked the behavioural patterns of A. bicinctus and then I choose five particular behaviours: spreading the dorsal fin and pectoral fins, presenting the broadside, jerk swimming, whipping with the caudal fin and attack. I took notes how often each of these behaviour patterns were carried out during one twenty minutes interval and I also took notes against which other reef inhabitants the anemone fish were aggressive. In the all together 1600 minutes of my observations I attend 208 attacks of A. bicinctus against other reef inhabitants. There was an obvious trend of aggression behaviour against Pomacentridae (Reef Perch), Labridae (Wrasse) and Chaetodontidae (Butterfly fish). Those families are food and territory rivals, egg and anemone predators. Serranidae (Grouper), anemone fish predators, were in the fourth place.
A. bicinctus lives in association with five host anemones: E. quadricolor (Bulb Tentacle Sea Anemone), H. magnifica (Magnificent Sea Anemone), H. crispa (Leathery Sea Anemone), H. aurora (Beaded Sea Anemone) and S. gigantea (Gigantic Sea Anemone). The number of the anemones in the area has a big influence on the social organization of anemone fish. In the investigated area, the number of anemones was a restrictive factor for adult A. bicinctus.
The results showed, that the method of the observations also has an influence on the behaviour of A. bicinctus. The fish showed more aggression behaviour when I was snorkelling. They are probably less disturbed without the noise coming from the diving equipment. At different depths the composition of the species is varying. This means that at different depths different enemies occur. The results showed, that the attacked species vary, not the behaviour of A. bicinctus. The size of the anemone fish has a big influence on the aggression behaviour.
Not only the number of attacks increases with it, but also the distance at which enemies are attacked. No attacks from juvenile A. bicinctus were observed. The frequency rises with the anemone size, as well as the distance at which passing fish are attacked. A change of the frequency of attacks during the day could not be proved. A. bicinctus showed before midday the most activity.

 

 

 

Miriam Reininger

Amphiprion bicinctus

Amphiprion bicinctus

Amphiprion bicinctus

Amphiprion bicinctus

Amphiprion bicinctus

Amphiprion bicinctus

Amphiprion bicinctus

Amphiprion bicinctus