Fish Aggregations

By June 30, 2020 No Comments

Fish aggregations are basically a large temporary gathering of fish, either single species or multiple species, repeatedly occurring at the same place and time. Reef Magic Cruises have a fish aggregation site close to the Marine World platform that occurs on the ocean side of a Reef Pass.

Reef passes are narrow channels that dissect a coral reef and allow for the inflow and outflow of water from the protected coral reef lagoon to the open ocean. Reef passes are well known fish aggregation sites on Indo-Pacific coral reefs. Fish may aggregate to perform a variety of vital task such as feeding, spawning, cleaning and social interaction (See fish aggregation videos).

Our research has monitored and studied a fish aggregation site for 15 years and has provided information on the biological and physical reasons why coral reef fish aggregate. (Insert or link Research video). Some of this information has also been published in the peer review journal PLoS One (open source).

Fisher EE, Choat JH, McCormick MI, Cappo M (2018) Relative influence of environmental factors on the timing and occurrence of multi-species coral reef fish aggregations. PLoS One 13:e0209234

Moore Reef Pass


Fish aggregations may play an important role in the resilience or function of coral reef systems. They provide energy sources to coral reefs and also replenishing fish populations.

Fish aggregation sites usually occur in outer reef environments where the coral reef meets the open water. Fish that aggregate to feed on oceanic plankton and the predators that aggregate to feed on these planktivores are introducing oceanic nutrients or an additional energy source into a coral reef system.

Coincidentally fish aggregating to spawn are subject to larger reef fish preying on their eggs, but also large pelagic predators preying on spawning adults (see Mac attack video). Definitely hard day at office for spawning fish, but this trade-off between predation and reproductive success assist in nutrient recycling, another important energy budget for coral reefs. Another important recycling component, although a bit gross, is fish that aggregate to feed on the poo of other fish (see poo feeding video).

Large coral reef fish of commercial importance that form large aggregations, are susceptible to overfishing. There are numerous cases from around the world, where fish stocks have been reduced drastically that aggregations do no longer form. If you overfish fish aggregating to spawn, not only are one generation removed but also future generations as well.

The functional role of fish aggregations need to be measured and included in the design of marine parks.