Ever since I first looked underwater more than 40 years ago, I have been fascinated by the diversity and number of fish on our reefs. Reef fish add color and movement to a reef and fish watching is a fascinating and rewarding activity for snorkelers and divers. Knowing the names of fish adds to one’s enjoyment, especially in later discussions of what was observed underwater or to identify a fish from an underwater photograph. Identifying fish is equally important for a student or a naturalist who wants to record the diversity of reef fish at a location. Reef fish identification guides were not readily available in Sri Lanka forty years ago, and I often used the names commonly used by local fishermen. Even today, there is a dearth of readily available, well-illustrated field guides for the informed layperson to identify accurately the reef fish found in Sri Lanka.
This field guide has been developed to fulfill this gap and assist both serious fish observers and informed layperson to identify reef fish found on our reefs. This book contains 169 illustrations of 158 reef fish species that can be seen both on coastal and offshore reefs. It provides basic information on each species based on published information and from my own experience of observing most of them underwater.
Today, reefs are under threat from several human activities — including destructive fishing, pollution and uncontrolled resource exploitation. Therefore, it is hoped that this field guide will spark an interest among the readers to play an active role in the conservation of these beautiful but vulnerable fishes.
There is no official count of the number of reef fish species that are found in Sri Lanka. A comprehensive survey of reef fish inhabiting coastal and offshore reefs is lacking. Lieske and Myers (1994) estimate that more than 900 species of reef fish may be found in Sri Lanka and the Maldives. Reef fish surveys conducted at several locations indicate that a single location may support between 300 to 500 species.
This field guide contains descriptions of 158 species of reef fish divided among 37 families. It has 169 illustrations to assist non-specialist observers to identify reef fish, while snorkeling or scuba diving. Information provided for each species is based on published literature and knowledge of the author since early 1970’s.
Habitats of reef fishes in Sri Lanka
The continental shelf of Sri Lanka supports many reef habitats. Reef habitats are patches of hard ground separated by areas of sand or mud, and are located at various distances from the shore. Reefs that are close to shore are called fringing reefs. They occur as a narrow belt around the coast. They may or may not contain a reef lagoon, which is a narrow body of water between the fringing reef and the shore. Examples of fringing reefs can be seen at Hikkaduwa, Unawatuna and Weligama in the South, and along the coast of the Jaffna Peninsula in the North.
Reefs that are located beyond the immediate vicinity of the coastline are called offshore reefs. In this document, the term ‘offshore’ is used to describe reefs that are located approximately two kilometers beyond the shoreline and up to the edge of the continental shelf.
Introduction Fringing and offshore reefs have been divided into three habitat types; coral, sandstone and rock reefs, based on the type of substrate visible to an observer.
Coral reef habitats are typically made up of living hard corals. Examples of coral habitats can be seen at Hikkaduwa and at Pigeon Island (Figure 1). Extensive coral reefs are located offshore in the Gulf of Mannar, at Vankalai, Silavaturai, Arrippu and Bar Reef. Other major coral reef areas are from Akurala to Tangalle in the South, Kutchchaveli to Kalmunai in the East and around the Jaffna Peninsula.
Sandstone reefs are widespread and are found nearshore, as well as offshore, up to the edge of the continental shelf. They support small patches of hard and soft corals. The majority are located along bathymetric gradients on the continental shelf, and are, therefore, approximately parallel to the coast (Figure 2).
Rock reef habitats are of hard rock, which is granite or a similar hard substrate and are part of the bedrock. Examples of rock reefs can be found along the coast in the south and in Trincomalee (Figure 3). Some can be seen nearshore, as well as offshore, when sections are above the water. Sometimes they form islands such as Pigeon Island in the East. Rock reef structures occur as patches or ridges on the continental shelf and beyond.
The depths of reef habitats vary from a about a metres in the intertidal zone to more than 100 metres near the edge of the continental shelf. The continental shelf is widest in the Gulf of Mannar and in the northeast, where reef habitats at a depth of about 50 metres can be found at a distance of about 35 kilometres offshore. The continental shelf is narrower in the South, therefore reef habitats at a depth of 50 metres are only about 10 kilometres offshore.
Reef habitats are often linked to seagrass meadows, mangroves and estuaries through transfer of nutrients and the migration of species. Some groups of reef fish — such as rabbit fish (Siganidae) — live among seagrass meadows and in mangrove areas during their juvenile stage and migrate to reef habitats as they mature.
Sourced from published literature