臺灣博碩士論文加值系統

一.黃錫鯛(silver sea bream, Sparus sarba)仔稚魚發育，就形態受化及生態特徵而言可分下列三個階段：(1)仔魚前期 (prelarvae)：遷長在3-4mm（孵化後5-6天），常溫下（20℃）約3天後開口而能攝食輪蟲，卵黃囊及油球於4-5天後消失。此階段游動時間較少，大部份時間浮於水表層，惟此時已有趨光性及趨流性。(2)仔魚後期(postlarvae)：從仔魚前期結束到變態期，體長約在4-11mm（約孵化後6-40天）。此階段後期能攝食豐年蝦，攝食前之魚體攻擊型態類似C-start型，即尾端彎屈使魚體成C形。水槽中觀察其棲息水層以中底層為主，並有避強光(2000-3000 lux)現象，餌料供應如不足，則會互相攻擊，攻擊部位以眼睛為主，腹部次之。(3)稚魚期(juvenile)從變態完成（約孵化後35-40天）到若魚期（約孵化後2個月，還長在25-30mm)之一段時期均屬之。
二.常溫下如不予餵食，仔魚於孵化後8天全部死亡，其PNR(point of no return)約在6-7天。其游動時間比較，孵化後4天餵食者即高於不餵食者，體長則於5天後餵食者大於不餵食者。孵化後的啟始投餌時間，以孵化後不同天數餵飼，求其經過10天之活存率，以3天時最高，依次為4，5，5天，顯示愈早投餌愈佳。
三.視網膜中視細抱之發育在變態期前柱細胞(rod)尚不易辨認，為"鈍錐細胞"(pure-cone)網膜。俟40天時在組織切片中已可清析分辨柱細胞，惟從變態前（約孵化後4週）發現有避光行為（為柱細胞發育之行為特徵），及現細胞核與錐細胞之比於35天時超過1，為柱細胞發育之輔證，其柱細胞發育應較組織切片所觀察之時間為早。亦即在變態前（28-35天)，網膜已具柱細胞。網膜中其餘各層細胞於孵化後即逐漸分化，到變態前即分化完成。惟剛孵化時仔魚並不具網膜色素，約3天後即可明題分辨網膜色素，並隨魚體成長而逐漸增加，其色素層之移動 (retinomotor response)，在體長為8mm（變態前）以後，較為明額。眼徑及水晶體之發育亦隨體長而增加，尤在變態期明顯增加，經依Tamara及Wisby(1963)之鑑別角公式Sinα=1/f[0.1(10+0.25)x2.0/n)求其視精度(acuity)，亦顯示於變態期顯著增強，而後漸趨穩定。
四.光照影響黃鍚鯛仔稚魚之攝餌可分：(1)從不同光強度下仔魚攝食輪蟲，稚魚攝食豐年蝦，在各種密度均呈現光強度高者有較大攝餌率。(2)以自然光照，24小時連續光照及日間暗適應，夜間光適應三組光照週期，以4小時為一時段，取不同成長階段之稚魚，分別以豐年蝦及蝦肉投餵，均發現攝餌週期與光照週期成正相關，即光照時段攝餌量較高，暗適應時段則較低，如改變光照週期，則其攝餌量亦隨之改變。而24小時光照，各時段攝餌量均無差異。此顯示黃錫鯛仔稚魚為日間光照的"視覺索餌者"(Visual feeder)。且其攝餌週期受外在不同光照而有所改變。(3)以長光週期(L/D=16/8)，短光週期(L/D=8/16)飼育對孵化仔魚成長之影響，發現長光週期有促進仔魚成長之作用，(4)在暗適應下，稚魚前期(TL=12~15mm)之攝食豐年蝦純賴逢機之被勸攝餌。而稚魚後期(TL=28~39mm)攝食則不純粹是被動之逢機攝餌、其剩餘豐年蝦數量遞減曲線，與被動逢機攝時之遞減曲線有顯著差異。

1.By the marphological and ecological characteristics, the development it larval Sparus sarba were divided into thrse stages: (1)Prelarvae stage(TL:3-4mm)(2)Postlarvae stage(TL:4-11mm) (3)Juvenils stage(TL:11-25mm)
2.The survival rate of the starved larvae was decreased with age after their mouths opened. All larvae died at the 9th day, and their PHK(point of no return) was between the 6th and the 7th day. Loconotion duration of the fed and unfed groups began to show the differences at the end of yolk-sac stage. Total lengths of these two groups showed significant differences after their oil gloubles were absorbed. Start feeding at the 3rd day had the highest survival rate.
3.Before the netanorphosis it was pure-cone retina. (Rods were not identified until the 40th day). The larvae showed negative phototactis at 28 days old. The density ratio of total photoreceptor nuclei to the cone numbers in the was greater than 1 at the age of 35 days old. It is likely that the rods appeared before metamorphosis. The newly hatched larvae have unpigmented and presumably functionlass retinae. On the 3rd day there was sparse pigment distributed. The retinomotor responses of the pigment aigration was synchronized with the period of their netanorphosis. The acuity of larvae depended on the focal length (which increases linearly with age) and on the density of cones. During the metamorphosis, the resolving angle decrease significantly. As the larvae grew, the acuity improved.
4.The effects of light intensity on feeding behavior as follows: (1)The higher of light intensity, the higher feeding rations in larvae and juveniles, (2)Under the natural photoperiod, continuous illumination and reverse photoperiod (illumination at night). The juveniles(TL:12-15 mm) fed artenias, the young (TL:30- 40mm) fed shriap meat. Both of their feeding amount were higher in light-period, and the feeding period was changed by light. It indicated that the larvae was "visual feeder", and the activity pattern was diurnal. (3)The growth rate reared in long photoperiods (L/D=16/8) was greater than those in the short photoperiods(L/D). (4)The juveniles(TL:12-15mm) under dark adaption, feeding artemias by chance and the young(TL:28-39mm) feeding without vision was not by chance alone.