João Paulo Krajewski

Nuclear-follower foraging associations of reef fishes and other animals at an oceanic archipelago

SynopsisFish species in many families and different trophic levels forage by following fishes and other animals. This interspecific foraging association was examined at an oceanic archipelago in the tropical West Atlantic. We recorded 27 reef fish species, two invertebrate species, and one turtle species playing the nuclear role, and 26 reef fish species acting as followers. The puddingwife wrasse following the spotted goatfish was the commonest foraging association recorded. The spotted goatfish was the nuclear fish that attracted the largest number of follower species (68% of the total number of follower species). The coney and the Noronha wrasse were the follower species that associated with the largest number of nuclear species (63 and 55% of the total number). About 20% of the reef fish species recorded in the archipelago engages in interspecific foraging associations. Substratum disturbance is a strong predictor for a fish displaying the nuclear role in the association, whereas the follower role may be predicted by carnivory. Nuclear species are diverse both in morphology and behaviour, and the nuclear role may be played either by fishes or other marine animals from invertebrates to turtles. Followers, on the other hand, comprise fishes only, which tend to display a more uniform feeding behaviour.

Meals for two: foraging activity of the butterflyfish Chaetodon Striatus (perciformes) in southeast Brazil

The banded butterflyfish (Chaetodon striatus) from the tropical and subtropical western Atlantic is a territorial, diurnal forager on benthic invertebrates. It is usually seen moving singly or in pairs, a few meters above the sea floor. We studied the foraging activity of C. striatus on rocky reefs in southeastern Brazil. This fish spent about 11 h and 30 min per day on feeding activities, and preferred colonies of non-scleratinian anthozoans over sandy and rocky substrata while foraging. The lowest feeding rates were recorded in the early morning and late afternoon, but we found no further differences between feeding rates throughout the day. We also found no differences between the feeding rates of paired and single individuals.

Does the association of young fishes with jellyfishes protect from predation?A report on a failure case due to damage to the jellyfish

The fish-jellyfish association is regarded as a temporary symbiosis believed to protect the fishes from predators. Here we report on juvenile scads (Trachurus lathami) associated with the jellyfish Chrysaora lactea, opportunistically preyed on by the grouper Mycteroperca acutirostris while the medusa was being damaged. The predation instances occurred when a couple of the filefish Stephanolepis hispidus approached the jellyfish to nibble on its umbrella. The feeding of the filefish caused a momentary disturbance of the defensive association, perceived and capitalised on by the watchful grouper, an opportunistic and versatile hunter. Before and after the disturbance, the protection offered to the young fish by the jellyfish showed to be effective, which strengthens the hypothesis of defensive function of this association.

Foraging activity and behaviour of two goatfish species (Perciformes: Mullidae) at Fernando de Noronha Archipelago, tropical West Atlantic

The goatfishes (Mullidae) include about 50 bottom-foraging fish species. The foraging activity of the yellow goatfish, Mulloidichthys martinicus, and the spotted goatfish, Pseudupeneus maculatus, was studied comparatively at Fernando de Noronha Archipelago, off coast of Northeast Brazil tropical West Atlantic. Pseudupeneus maculatus fed over a larger variety of substrate types, had lower feeding rate, roamed more per given time, spent less time in a feeding event, and displayed a more diverse repertoire of feeding modes than M. martinicus. The differences in the foraging activity and behaviour between the two species possibly minimize a potential resource overlap, as already recorded for other sympatric mullids. Pseudupeneus maculatus had lower feeding rate most likely because it feeds on larger items, and roamed over greater distance per time. Possibly this is because it foraged over a greater variety of substrate distributed over a larger area than that used by M. martinicus. Notwithstanding the overall morphological and behavioural similarity of goatfishes in general, they do differ in their substrate preferences and foraging activity, which indicates that these fishes should not be simply considered generalized bottom foragers.

Patterns of variation in behaviour within and among reef fish species on an isolated tropical island: influence of exposure and substratum

Here we studied the activity budgets of nine common reef fish in the oceanic archipelago of Fernando de Noronha, off north-east Brazil. Species were variable in their behaviour between different sites and similarities in their activity budgets were not necessarily associated with their trophic group. For four species we investigated the relationship of their activity budgets to wave exposure and substratum composition. Staying close to the substratum was positively correlated to wave exposure for most species and foraging was negatively correlated to exposure for two species. By behaving this way, these fish may save energy by avoiding swimming in higher water flux. In contrast to relationships with wave exposure, the responses to substratum composition were species specific. Our results highlight that the activity budgets of fish living in oceanic rocky reefs can be variable and influenced by the local and temporal variation in environmental variables.

The glassy sweepers' way: seeking a versatile wrasse to be cleaned

Peixes recifais diurnos compoem a maioria dos clientes nas estacoes de peixes limpadores. Entretanto, algumas especies com habitos noturnos tambem procuram os peixes limpadores, ficando expostas a potenciais predadores diurnos quando precisam deixar seus abrigos. Registramos aqui as interacoes de limpeza entre um labrideo diurno (Thalassoma noronhanum) e um cliente com habitos noturnos (Pempheris schomburgki), que permanece abrigado durante o dia. Esta especie de cliente deixa seu abrigo durante o dia e nada em direcao a T. noronhanum quando este limpador desloca-se proximo aos esconderijos. Uma vez que T. noronhanum e capaz de manter estacoes de limpeza temporarias, proximas aos abrigos dos clientes, P. schomburgki diminui uma possivel exposicao aos predadores quando procura esta especie versatil de limpador.

The association of the goatfish mulloidichthys martinicus with the grunt haemulon chrysargyreum: an example of protective mimicry

Descrevemos aqui um possivel exemplo de mimetismo de protecao entre o saramunete Mulloidichthys martinicus (Mullidae) e a xira Haemulon chrysargyreum (Haemulidae), no Arquipelago de Fernando de Noronha, Nordeste do Brasil. O saramunete e a xira sao semelhantes entre si, no padrao de coloracao e no formato do corpo. Observamos que estas duas especies formam cardumes mistos regularmente, ao redor de recifes. Quando perseguidos, pequenos grupos isolados de saramunetes se associam aos cardumes de xira e se comportam de modo semelhante as xiras. As semelhancas de formato e coloracao entre as duas especies provavelmente facilitam a formacao de cardumes mistos e aumentam a protecao contra predadores visualmente orientados, para ambas as especies. Assim, acreditamos que a associacao protetora entre o saramunete e a xira pode ser considerada como um tipo de “mimetismo social”, uma vez que nenhuma destas especies e venenosa, peconhenta ou tem fortes estruturas mecânicas de defesa. Sugerimos, ainda, que exemplos adicionais de mimetismo social possam envolver o saramunete e outras especies listradas de Haemulon.

Wolf in a sheep's clothes: juvenile coney (Cephalopholis fulva) as an aggressive mimic of the brown chromis (Chromis multilineata)

We found yellowish juvenile coneys (Cephalopholis fulva) at Fernando de Noronha Archipelago, off Northeast Brazil, joining schools of similarly sized and coloured brown chromis (Chromis multilineata) when these latter closely approach the rocky reefs. Mingled within the mid-water hovering group of the plankton-feeding chromis, the piscivorous coney is able to approach unaware prey - an instance of aggressive mimicry. Three out of four coney individuals hunting under such disguise were successful in their attempts to prey on the otherwise wary rock-dwelling blenny (Malacoctenus species). This is the first instance of an epinepheline grouper mimicking a schooling and plankton-eating damselfish model in the West Atlantic.

Octopus mimicking its follower reef fish

We describe a possible example of social mimicry between Octopus insularis and the small grouper Cephalopholis fulva, which frequently associate during foraging at Fernando de Noronha Archipelago, Brazil. The octopus, when swimming backwards, jet‐propelled, becomes similar in colour and shape to accompanying C. fulva individuals and is therefore less conspicuous within the fish group. We regard this as an instance of social mimicry, a form of protection against visually‐oriented predators in which different species similar in shape and colour mingle for the advantage of grouping. Even when swimming backwards alone, O. insularis may become similar to foraging C. fulva individuals, another putatively protective behaviour. We suggest that the feeding association commonly found between O. insularis and C. fulva minimized the evolutionary costs for the origin of mimicking by the octopus. †Retired and associated as voluntary researcher.

Cleaning by the occasional cleaner Diplodus argenteus (Perciformes: Sparidae) in south Brazil: why so few client species?

Here I record the cleaning activity of the occasional cleaner Diplodus argenteus at rocky reefs off southern Brazil. Diplodus argenteus juveniles are referred to as occasional cleaners, but there is no further description of their cleaning activity in the literature. Only two fish species were here recorded as clients, which I hypothesize to be related to a lack of visual attractiveness of D. argenteus cleaning services.