Fish and fishes People often ask about how the terms 'fish' and
'fishes' should be used. In fact it is often said that there is
no such word as 'fishes'. This is not true. A group of fish of
the same species are called 'fish'. Two or more species of fish
are called 'fishes'. For example, a number of Eastern Australian
Salmon swimming together can be called a school of fish. But if
one Tarwhine starts swimming with the Eastern Australian Salmon
they are called fishes. Books such as the Sea Fishes of Southern
Australia and Coastal Fishes of South-Eastern Australia use the
term 'fishes', because more than one species of fish are
included in the book. For more information, view the Wikipedia
comment on Fish or Fishes? Mark McGrouther , Collection Manager,
Ichthyology