![]() For example, this might suggest that creating more foraging habitat would enhance the fishery, or may suggest that removing some fish would actually help fishery performance. This can be an early warning sign that a closer look or management measures are needed. If the population is slow growing or stunted it can suggest there isn’t enough food available, or something else is acting as a pressure on the fishery.Īgeing fish of different types and sizes can tell us a lot about the health of a fishery If fish are eating well, in healthy environments, they can grow well too – we have developed growth rate baselines that we use to compare the growth rate of fish populations across the country. Essentially, the growth rates we’re looking at can tell us how much food is available to fish. Competition and fishery performanceįish ageing across populations can reveal competition between species and provide an indicator of how well a fishery is performing. We have worked on a number of projects to confirm the success of stocking and even aged record-nudging fish that have been both farmed and spawned naturally. It also removes the need for more costly or invasive tracking options like dyes and tags. We have aged 3lb perch at just 3 years old, and chub of 6lbs to both 11 years and 17 years.īy spotting these false checks and changes in growth it is possible to track stocked fish, tell how well they are doing in their natural environment and whether stocking has been successful. Interestingly, fish size is not always a reliable indicator of age. ![]() However, most scales remain in place and if we look at a scale that has been present on the fish its whole life we can assess how old it is.Īs the years rack up it can become harder to accurately age a fish, but that’s where the skill and experience of the scientist comes in. Fish of all agesįish naturally lose scales during their life and with them goes the ability to read its life history. Through further analysis of the circuli, we can also evaluate the growth of the fish throughout its life and pinpoint landmark events such as when it was stocked, spawning events, and in some cases, even where it has been to feed. By counting the winter bands of reduced growth, we can age the fish. These dark bands are termed ‘circuli’ and it is the spacing between these circuli that we use to determine the age of a fish.ĭuring winter the spacing between the circuli is less due to slower growth of the fish, whereas in summer, the circuli are spaced further apart as the fish feeds and grows more quickly. If you removed a scale sample from a fish and observed it under a microscope you would see numerous dark and light bands radiating out from the centre, or focus, of the scale. Taking scales from fish is harmless and lost scales will regrow allowing fish ageing to be applied to fisheries of all types and sizes, and to the great majority of species from salmon to carp and tench to tarpon. At the NFL, experts in fish ageing can read these marks opening up a whole new world about each and every fish within the population. ![]() A scale sample can tell us not only how old a fish is, but much about its lifestyle and environment! The scale tells the storyĪs fish grow, their scales grow with them, laying down marks a bit like rings on a tree.
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