Otoliths, Finrays, scales, and opercula

Otoliths, finrays, scales, and opercula are tissue in fish that grow over the lifespan of the fish and can therefore, represent changes occurring in the life of that fish. For example, these tissues can monitor 1) occurrence and timing of migration in anadromous fish species; 2) how the introduction of mine effluent has influenced metal concentrations in local fish populations; 3) the effectiveness of water treatment on aquatic ecosystems by comparing pre-treatment with post-treatment portions of the growth structure; and, 4) in old fish (>10 years), the state of water quality in an aquatic system from many years previous.

Click here to learn about how barium and strontium in an otolith can help determine if and when a fish migrated to the ocean from freshwater.