It is assumed that younger fish are sexually immature while older fishes are sexually mature. Can this knowledge be applied in any way to the estimation of fish age?
I wasn't necessarily referring to gonad weight, it may be physical description of the gonads or something with a bit of reliability. It may not be applicable to a wide range of species, but i need to know whether there is a smallest possibility of estimating the fish age from gonadal information.
Maybe possible for fish with life expectancy less than or equal to one year (if any). But to me it is not possible for other fish species.
To my my I think it would be remotely possible with a very high degree of knowledge of the species reproductive development and the environmental parameters of its area of collection. Would most likely be possible for specimens from a controlled environment (tank or pond).
Perhaps if species are short lived as mentioned by Rahman, and semelparous. For many species, gonad development (in particular, gonad mass) is proportional to the size of the fish. Age and size of the fish are (to some extent) correlated, and gonadal mass is thus a product of fish size. Perhaps gamete quality could be a reliable representative of fish age in some species...?
Several species attain maturity at a younger age under certain conditions (stunting). It would be unwise to rely on gonad maturity or GSI to estimate age.
Dear Juan, your point is not clear,do u mean some species attain maturity at smaller sizes or younger ages? because stunting means suppressed increase length which may be linked to a number of factors including temperature.
Pls also remember my emphasis is not on the accuracy of the method but the slightest possibility of successful aging of fish using gonads particularly for fish in the wild.
You are correct, dear Azubuike; stunting directly affects size, but it can also affect age. Besides temperature, it can be induced by population density. But, returning to your emphasis: perhaps yes, one could at least crudely infer that a mature gonad means a fish above a certain age, the age-at-first-maturity (although this age is expected to be very variable between populations).
Hi Azubuike
It is difficult to determine exactly the age of a fish from the level of its gonadal maturity as:
1. Under some environmental conditions (ambient water temperature, toxicants) gonads may get matured even in fishes at a tender age.
2. Under another set of environmental conditions (availability and type of feed, pollutants, diseases etc.) gonads may not mature even in a fully grown-up fish.
3. Some fishes undergo sex reversal as well.
However, age could be determined from the level of the gonadal maturity in fishes that are well studied for their biology or might have grown in controlled environmental conditions.
These articles may be of some help to you:
1. http://icesjms.oxfordjournals.org/content/67/9/2033.full
2. http://docs.lib.noaa.gov/noaa_documents/NOS/OMA/TM_NOS_OMA/nos_oma_29.pdf
Best
Dola
Tanx Dola, the articles were quite informative and already raising more questions in my mind. Tanx again.
Nobody do it.Each species has it's physiology.But you may estimate age of your fish by conventional methods: by scale or otholithes.
I am perfectly agree with you Rita!
Otoliths is a conventrional methods. Sometimes, the development of yolk sac could be a good criteria for larvae age.
Added to all points above,
as the maturity stages are going regurarly, it seems quite impossible to determine the age based on gonadal improvements, specially when it comes to long-live species. However, it might be fair for short-lived species, although it there would be a lot of fatcors (environmetally and species specific) that need to be considered fully, which need in itself an epertise knowledge. From where I am standing, however, there might be some relationship between the fish age and the quality og maturity stages, atresia for instance.
Wish you well in your project,
Mehdi
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