1. Why are age and growth of fishes important to estimate? 2. How are fishes age

Question

1. Why are age and growth of fishes important to estimate?

2. How are fishes aged? What’s the most common method and what fish parts are used? What are the advantages and disadvantages of the methods? How is the length frequency method used?

3. Why are scales for aging selected at different locations for different species? Why not take scales from the lateral line? How many scale should you take? What are 2 common types of scales found on fish (more primitive vs. more advanced fish) (didn’t get to this in 2015)?

4. What kinds of things can you do with age data on fish? How can you back calculate the length of a fish at a previous age? How do you estimate a fish’s growth rate? How do you cut out the otoliths of a fish?

5. Terms: growth rate, total length, fork length, standard length, length-frequency histogram, YOY, otolith,

6. What is Lee’s phenomenon? (not covered in 2015)

Explanation / Answer

1. Answer : Age is the important parameter in stock assessment and maintaining record and data of these fishes.

2.Answer: Age is determined by counting natural growth ring on the scale , otoliths ,fins and eye lenses . Advantages ; Age counting help in keeping record of different fishes.Length frequency method used for counting age of fishes it involve counting on hard part ( scale, vertebrae, fins ) The counting of growth increment on otoliths is employed

3.Depending on species scale samples are taken differently because in different species scales location differs for example introut circulinear centre of scale become compressed and difficult to read.lateral line are sense organ of fishes so scale are not taken from that part.

Placoid scale is found in cartilagenous fishes like shark while leptoid scale found in bony fishes

6.Common finding that in older fish population forms with more narrow annual scale ring or more narrow growth zones are more frequent than in younger populations is lee phenomenon.

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