MenuMain navigation

Glossary

Some of the terms used in this atlas may be unfamiliar to amateur biologists, and so I provide this glossary. The definitions provided here relate only to the way the terms are applied to fish.

Adipose eyelid – thick, fleshy tissue that surrounds and partly covers the eye

Adipose fin – a small fleshy lobe on the back between the dorsal fin and caudal fin

Aestivate – to be inactive during warm or hot, dry periods

Anadromous – refers to fish that mature in the sea but migrate to fresh water to breed

Anal fin – the unpaired fin on the ventral or underside of the fish just behind the vent. The base of the anal fin is where it joins the body. To determine if the anal fin is short or long based, press the fin up flat against the body. If the base of the anal fin is shorter than the longest ray in the anal fin then the anal fin is short-based. If the base is longer than the longest ray, then the anal fin is long-based.

Barbel – whisker or finger-like appendages around the mouth

Benthic – living on the bottom

Caudal fin – tail fin

Caudal peduncle – the slender part of the body from the base of the anal fin to the start of the caudal fin

Chevron – V-shaped

Detritus – material from decomposing plants and animals

Diadromous – refers to fish that make migrations between the sea and fresh water, may be in either direction and not necessarily related to spawning

Dorsal fin – an unpaired fin on the back; there may be up to 3 dorsal fins

Endemic – native and restricted to a particular geographic area

Ephemeral – water bodies that are not permanent

Estuary – the area at the mouth of a river that is affected by the ebb and flow of tides

Family – a taxonomic category containing a single or many genera

Fecund – fertile; producing large numbers of eggs

Fin ray – a bony rod supporting a fin. Rays are usually branched into two halves (side by side), are often segmented, and usually flexible

Fin spine – a bony rod supporting a fin that is not divided unto two halves. Often spines are stiff and sharp

Forked – refers to the posterior margin of the caudal fin – deeply indented

Fragmented – broken up

Genus – a taxonomic category containing a single or many species

Gill opening – the exterior opening of the gills – located just behind the head. Gill openings may be covered by a bony plate (the operculum) or soft flaps of skin

Gill membrane – a fleshy flap on the back of the operculum used to allow the gill opening to be closed

Gonopodium – a specialized part of the anal fin in male Poecilidae that is used to transfer sperm to female fish

Indigenous – native but not restricted to a particular geographic area

Kype – an upward turning hook that develops on the lower jaw of some male Salmonidae during spawning

Larvae – newly hatched young

Lateral line – a series of pores in the skin along the side of the fish, usually about halfway down the side

Nocturnal – active at night

Non-diadromous – fish that do not make migrations between the sea and fresh water

Pectoral fins – paired fins (one on either side of the body) located just behind or below the gill openings

Pelagic – living in open waters near the surface

Pelvic fins – paired fins (one on either side of the body) located on the ventral side of the fish between the head and the vent. Pelvic fins are not always present, e.g. mudfish

Phytoplankton – tiny floating aquatic plants (algae)

Posterior – the rear or tail end

Redd – a nest excavated on the substrate by female Salmonidae

Rounded – refers to the posterior edge of the caudal fin – a convex curve

Scales – thin, overlapping plates of a hard substance that protect the skin of fish. The easiest way to tell if a fish has scales is to run your finger along the side of the fish from back to front. If the fish feels smooth and slippery, it has no scales or the scales are embedded within the skin; if it feels rough and your finger catches, then it has external scales.

Scientific name – the taxonomic name for a species, consisting of two words, the genus and species

Serrated – notched like a saw blade

Species – a taxonomic category of individuals or populations capable of breeding among themselves, but not usually with other individual or populations

Substrate – the bottom or material making up the bottom of a river or lake bed

Taxonomy – the study of the classification of living organisms, including rules and systems of naming organisms

Vent – the posterior, external opening of the gut; the anus

Ventral – the lower surface of the body

Vertebrae – the individual bones or segments that form the backbone. Vertebral count refers to the number of bones found in the backbone

Whitebait – juvenile fish of the Galaxiidae family; generally used in reference to the diadromous species only