New Study Discovers Blennies and Gobies Are The Main Fish Consumed on Reefs

A fire goby (Nemateleotris magnifica), Bali, Indonesia

By Max James

Scientists think they have discovered how coral reefs flourish with such abundance in the relatively empty and low-productive environment of the open ocean, and it's all down to blennies, gobies, dottybacks and the host of other fish that form what is known as the cryptobenthics.

The ocean's smallest vertebrates are the fast food larder of the reef. A study published in Science this month estimates that cryptobenthics account for about 60 per cent of the biomass consumed on the reef and they generate two-thirds of reef-fish larvae in the pelagic zone surrounding reefs.

Splendid dottyback, Raja Ampat, Indonesia

Bryozoan goby, Ambon, Indonesia

The study said: ' While cryptobenthics are commonly overlooked, their unique demographic dynamics may make them a cornerstone of ecosystem functioning on modern coral reefs.'

It is the cryptobenthics - literally hidden bottom dwellers - ability to grow, reproduce and die at such a phenomenal rate which provides the fuel to keep reefs so healthy.

Simon Brandal, lead author of the report, from Simon Fraser University, Canada, said that by analysing field data and using population modelling, his research indicates that a full 70 per cent of cryptobenthics are devoured every week. They reproduce, hatch and grow at such a phenomenal rate that new individuals are constantly replacing those eaten.

Yellow pygmy gobies in a bottle on a reef

These tiny fish - mostly smaller than 5cm - come from 17 different families including gobies, blennies, dottybacks, clingfishes, dragonets and seahorses. And there is a vast profusion of different species in each family. It is thought that there are more species of goby than any other type of fish - more than 2,200 identified so far.

It is even more surprising, considering how important they are in the food chain, that their small size limits the number of eggs individuals can produce. This probably accounts for the common habit of being extremely dutiful in incubating their eggs - many are mouth brooders, seahorse males carrying their eggs in breeding pouches and sandgazers carry a ball eggs under their pectoral fins (known as armpit breeding).

Yellow-headed jawfish with eggs in mouth, Little Cayman

Another remarkable feature of cryptobenthics is that they tend to have extremely short life spans. They pygmy goby, for example, has the shortest life span of any vertebrate - two months in total, most of which is spent at the larval stage.

All these factors are the reason why the crucial role of these fish has not been previously understood. The standard way of measuring the biomass of fish on the reef by a survey would not indicate their importance - at any given time their biomass it is relatively small, it is just that they are eaten and being replaced with such stunning regularity.

Pygmy goby on a sea fan - the vertebrate with the shortest lifespan