Why is ageing fish important?
Ageing fishes is a vital part of fish stock management. Ageing is also important for the monitoring of fish populations and their reaction to environmental impacts such as fishing, natural mortality, and predation. This management will help aid in more long term monitoring and management of fish stocks to create sustainable fish stocks.
Our sample area focuses on two survey areas of the Chesapeake Bay and the Northwest Atlantic Ocean from Cape Hatteras, North Carolina to Martha’s Vineyard, Massachusetts. The Chesapeake Bay is the east coast’s largest estuary which makes it an essential body of water to monitor. This coupled with the near shore survey in the Atlantic provides sample coverage for many commercially valued species which should all be carefully monitored.
A variety of methods are used to age fish. Scales, vertebrae, spines and otoliths are a few of the hard calcified structures that are commonly used to age fish. Scales and otoliths, the fish’s ear bones, are the two most common that our group samples. Within choosing a calcified structure to read there are a variety of methods to read a process those samples. Scales can be pressed into an acetate medium where annual marks can more easily be read. These annual marks are also visible on whole otoliths and can also be further examined by sectioning the otolith. Our group has been recently working on a comparison study between scales, whole otoliths and sectioned otoliths to find which part provides a clearer more accurate read.
To further elaborate, annual marks or annuli are formed by environmental factors like water temperature is association with the change in seasons. Water chemistry, salinity and population density can also be factored into the formation of annuli. Spawning often coincides with annuli formation. Many of the fishes we sample form annuli during their spawning season.