when we practice about fish breeding, we learn how to identifying and selecting of fish gonad maturity. the best technique for this kind based on nucleus migration. egg should be taken using intra ovarian biopsy by canulator or flexible tube. after immersed in serra/clearing solution for 3-5 minutes, nucleus migration could be observed under microscope. usually, nucleus position uniformity of 80% used as reference for gonad maturity judgment.
other way, we might measure eggs diameter under microscope completed with micrometer. compared to eggs diameter standard (different in each species), we could to determine of gonad maturity.
in the field practice, serra solution and microscope often un-available. So, we couldn’t use both nucleus migration and measured eggs diameter. in the point of view aquaculture dissemination to small scale fisherfolk, it’s important to introduce of practical method to judgment of gonad maturity which representative for fish breeding.
using flexible tube (feeding tube that available for human), eggs might be taken by intra ovarian biopsy. it’s easy but should be carefull. instead observed under microscope, eggs spread on hand and estimate of eggs diameter uniformity, direct visually (fortunately, most of tropical people have dark color in hand, so easier to observe eggs).
if most eggs (about 80%) seen uniform (independent from how width eggs diameter), gonad has be mature and ready to breed. if there are transparant eggs (estimate up to 20%), gonad has be over-ripe. and if there are too many small eggs (estimate up to 20%), gonad has been growing. brooder with over-ripe or growing eggs should not be used for breeding. in the case of over-ripe, usually easy to strip for eggs release but low in fertilization/hatching rate. and growing eggs, usually failure in eggs discharge or, if released, low in fertilization hatching rate.
note: thanks to aquaculture officer in Fish Seed Center of Gorontalo Province that warmly collaborate to practice of siamese catfish breeding. good luck to you!