臺灣博碩士論文加值系統

橈足類生物為海洋浮游動物組成中的主要生物，在遠洋生態系裡扮演食物鏈底層與高層之間能量傳遞的要角。於自然環境中，肉食性魚類的魚苗偏好以活體餌料為食，而橈足類為最常見的餌料生物之一。從養殖的眾多橈足類品種中提供優良之活體餌料生物給魚苗，主要的目的在於提昇魚苗的存活率以及品質。現實生活中，由於橈足類的適當體型以及高營養價值，使牠取代輪蟲與豐年蝦成為重要活體餌料的候選生物。在水產養殖業應用上，飼養當地原生橈足類為最佳首選，因為當地物種取得容易，也已適應當地環境及氣候條件，但就穩定供應的技術條件上，仍有待克服。為了建立必要的基礎知識，本研究試圖以丹麥及台灣兩地的半集約式橈足類養殖方式，來描述遠洋生態系食物網動態。在丹麥，橈足類被飼養來作為鰈魚魚苗的活餌，在台灣則用以餵養石斑魚苗。過去三年，這些地區主要養殖的橈足類之生態學、生物學、生理學及養殖技術已有了初步研究。
在丹麥，橈足類的豐度成為鰈魚魚苗維持高存活率的限制條件。通過對營養素的控制研究，實現了提高浮游植物生物量，從而促進了橈足類的健康，提昇了養殖密度，這將可大量供給於魚苗之養殖。雖然研究成功提高了橈足類的養殖密度，但是高營養鹽的添加使得浮游植物的優勢族群從矽藻轉變成渦鞭藻。營養素的添加導致 pH升高與渦鞭藻出現，降低魚苗存活率，也讓橈足類的優勢種類由 Acartia spp. 變 Centropages hamatus。除此之外，在養殖末期移除海水後發現大量 Acartia spp. 的休眠卵出現於繁殖槽之沉積物中。這些卵可以被收集、儲存並且在鰈魚魚苗開始攝食時孵化加以利用。當鰈魚魚苗開始攝食時，營養豐富的橈足類配合休眠卵的收集便能提供充足的活餌。此外，橈足類繁殖槽與魚類養殖槽隔離，可以避免魚苗因水質問題產生不必要的死亡。
在台灣，橈足類的養殖與牠們的生產力紀錄首次被描述。橈足類種群具有物種多樣性低以及種類組成單一（最主要的種類為Pseudodiaptomus annandalei）的特點。初步的研究中發現P. annandalei 為最佳的活餌候選品種，因為牠對於不同的養殖條件具有很強的適應力、成長快速並且富含脂肪酸。為期一年的研究表明，即便環境條件明顯改變的狀況下，橈足類的生產力與豐度仍能保持穩定。然而，相較於初步研究，有些橈足類其成長速率低、脂肪酸的組成成分不同，顯示出橈足類成長取決於水體中所存在之食物，例如浮游植物與作為肥料的魚肉。由於漁民收集橈足類成體與亞成體來當石斑魚苗的活餌，橈足類的無節幼生卻完全不被考慮拿來利用，因此養殖池中具有相當高的豐度。為了增加漁民的收入，亦考慮到漁民不能中斷捕撈的壓力，我們推估現有橈足類成體與亞成體的收成量可以翻倍；而且，橈足類的無節幼生也能收集加以販售，用來作為石斑之外魚苗的初期餵食活餌。
綜合兩地的比較研究，得以更深入了解餌料用橈足類的特性，並針對如何提升橈足類的飼育技術，為台灣與丹麥兩地的養殖業者提供有效建議。

Copepods, as the main component of the meso-zooplankton, play an important role in pelagic systems in linking the lower trophic levels to the highest ones. In natural environments, carnivorous fish larvae prefer to capture and consume live feed, and copepods represent one of their most common food items. To provide a superior live feed for fish larvae in aquaculture, species of copepods are used aiming to increase the survival and the quality of the fish. In fact, copepods are interesting candidates to replace rotifers and Artemia due to their adequate size and higher nutrient content. In the aquaculture industry, native copepod species are preferred due to their adaptation to the local climate and environmental conditions, but their availability in terms of biomass is still an issue to solve. To establish necessary fundamental knowledge, the intent of the study was to describe the pelagic food web dynamics in two semi-intensive copepod farms. In Denmark live copepods are cultivated to feed turbot larvae, while in Taiwan they are cultured for grouper larvae feeding. The ecology, biology, and physiology of the major copepods species as well as farming techniques were studied over the course of 3 years.
In Denmark copepod abundances in production tanks were defined to be insufficient to sustain high survival rates of turbot larvae. A manipulation study with the addition of nutrients was accomplished to boost phytoplankton biomass and cascade into better fitness of copepods which, increasing in density, will fulfill the needs of the fish larvae. The study was successful, and higher density of copepods was reached, however the high level of nutrients governed the phytoplankton community that changed from diatom dominated to dinoflagellates. High pH and the presence of nuisance dinoflagellates reduced the survival of fish larvae in nutrient amended treatment and caused a shift in copepod species, with Acartia spp. taking over Centropages hamatus. Furthermore, resting copepod eggs of mainly Acartia spp. were found in great amount in the sediment of the tanks after the removal of seawater at the end of the production cycle. Those eggs could be collected, stored and hatched at the exact time when the turbot larvae start feeding. The use of nutrient-enriched copepods and the collection of resting eggs would potentially solve the need of adequate prey field when turbot start first feeding. Moreover, copepod production tanks would be separated from fish tanks to avoid water quality issues causing unwanted mortality.
With regard to Taiwan, this study presents the first description and recording of copepod cultures and their productivity. The copepod community in Taiwan was characterized by low species diversity and revealed no differences in species composition, with Pseudodiaptomus annandalei as the main species. The first campaign revealed that P. annandalei is an optimal candidate for live feed considering its strong resistance to different culturing conditions, fast growth and high FA content. During a yearlong study, the productivity of copepods and abundances remained quite stable, even though environmental changes were observed. However, copepod growth was lower compared to the first campaign and differed in FA composition, indicating that growth was dependent on the food available in the water column, considering both the type of phytoplankton and fish meal used as fertilizers. It was perceived that farmers exclusively collected adult copepods and copepodites as live feed for grouper, whereas nauplii, found in great measure, were not considered. To increase the income of the farmers, taking into consideration the sustainable actual harvest pressure, we estimated that the copepods and copepodites harvest could be doubled; moreover, nauplii could also be collected and be sold to feed fish larvae other than grouper at first feed.

This comparative study leads to a better understanding of copepod farming for use as feed for fish larvae as well as it helps to draw recommendations on how to improve the copepod aquaculture industry in both Denmark and Taiwan.

Table of contents:

Acknowledgements
Abstracts
1. Introduction to aquaculture
2. Live feed in aquaculture
3. Copepods as live feed
4. History of research in “copepods and aquaculture”
5. Copepod cultures
5.1 Copepod culture systems
6. The Ph.D. project: assessment of two semi-intensive copepod systems
6.1. The Danish system
6.2. The Taiwanese system
6.3. Relevant copepod species
7. Aim of the study
8. Main findings
8.1 Comparison between the two semi-intensive copepod systems
9. Conclusions and future recommendations
10. References
10.1 References for chapter 4
11. Manuscripts

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