' 'I \ \\{ 32 Technical Report Series 32 I Number 73-7 A MANUAL OF FLATFISH REARING J by David B. White and Robert R. Stickney 31 31 Georgia Marine Science Center University System of Georgia Skidaway Island, Georgia 81 A MANUAL OF FLATFISH REARING by David B. White and Robert R. Stickney Skidaway Institute of Oceanography P. 0. Box 13687 Savannah, Georgia 31406 September 1973 The Technical Feport Serits of the Georgia Mari.ne Scie nce Center is issued by the Georgia Sea Grant Program and the Marine Extension Service of the University of Georgia on Skidaway Island (P. 0. Box 13687, Savannah, Georgia 31406). It was established to provide dissemination of technical infor­ mation and progress reports resulting from marine studies and investigations mainly by staff and faculty of the University System of Georgia. In addition, it is intended for the presentation of techniques and methods, reduced data and general information of interest to industry, local, regional, and state govern­ ments and the public. Information contained in these reports is in the public domain. If this prepublication copy is cited, it should be cited as an unpublished manuscript. Table of Contents I. Table of Contents . 11 II. List of Tables . 111 II I. List of Figures . • . • • • 1v IV. Introduction . ............................ 1 V. Culture Facilities at Skidawav Institute of Oceanography . • . • . • 2 VI. Basic Culture Techniques . 4 Supplies of Eggs for Culture. • • • • • . • . • . • • . • • • • • • 5 Larval Food and Disease Control 8 Collection and Care of Postlarvae and Juveniles 12 Nutrition of Postlarvae and Juveniles . 13 Environmental Conditions for Paralichthys Culture • . • . • • • 18 VI I. Conclusions and Recommendations 19 Choosing the Site for Culture . • . • . • . 19 Building the Physical Plant . • . • • . • • . • • • 21 VI II. Bibliography . • . 25 IX. Tables . ... • . 28 X. Figures . .. 31 ii List of Tables Table 1 Selected Environmental Parameters of some Laboratory Reared Flatfish . 0 • • • • • • • • • • • • • • • • • • • • • • • • • • 28 Table 2 Essential Amino Acid Requirements of Plaice and Sole ..••.•.. 29 Table 3 Composition of Artificial Pelleted Diets of Cowey et al (1970) and Stickney and White. • • . • • . • • . • . • • • . 30 iii List of Figures Figure 1. Flatfish under culture at the Skidaway Institute of Oceanography: Paralichthys dentatus (bottom) and Ancylopsetta quadrocellata • . 31 Figure 2. Fiberglass swimming pool filters used for secondary filtration . .. 32 Figure 3. View of water table with aquarium sized fiberglass tanks in which postlarval fish are maintained. • . • . • . • 33 Figure 4. Schematic of 1 meter diameter fiberglass tanks for rearing of juvenile flormder . 34 Figure 5. The lower side of a Paralichthys dentatus demonstrating both ambicoloration and extensive papillomas associated with an outbreak of the virus Lymphocystis. • . • • . • • • • • 35 Figure 6. Growth of Paralichthys dentatus during 1972 and 1973 demonstrating increased growth caused by physical plant improvements between those years. 36 lv INTRODUCTION Severe worldwide protein deficiencies that are evident today and promise to increase with the Earth's population have made man aware of one of his last apparent exploitable sources of food -- the sea. However, with our current knowledge of the world ocean as an ecosystem it has become increasingly clear that man is presently exploiting this system at close to its maximum sustainable yield (Ryther, 1969). This fact, coupled with the enormous expense and legal problems that arise when a country maintains a national fishing fleet which fishes the coastal waters of other nations has caused many countries to look into the potential for management of sections of the oceans in an attempt to increase the yield per unit area and thus to minimize the cost of harvesting food from the sea. Culturing of aquatic animals~ se dates back at least two thousand years; however, most of the knowledge gained by early culturists was not recorded and hence is lost to present generations. The late nineteenth century saw an awakening of interest in the rearing of aquatic organisms in North America. At that time effort was mainly directa:i toward the augmentation of commercial fisheries by the release of large numbers of hatchery reared larval and postlarval forms into the oceans. Tremendous amounts of capital and energy were thrown into work in this area and consequently a considerable amount of knowledge was collected on spawning and rearing techniques, although attempts at supplementation of nat­ ural populations were eventually abandoned when they proved ineffective. The flatfish (Pleur onectiformes) as a group were well represented in this early research 1 and information on this group began to appear in scattered publications as early as the 1880's. In the 1920's financial hardships and unfavorable returns from their efforts caused the closing of many hatcheries. Within this period of time, however, flatfish became established as suitable animals for laboratory studies due to their ease of maintenance. For this r eason scattered information has been compiled until the present. The object of this report is to gather the pertinent flatfish literature, to condense the most relevant information and to present generalized procedures and recommendations for the production of marketable flatfish from eggs. The techniques presented in this paper were taken from the literature and from work conducted at the Skidaway Institute of Oceanography on three species of flatfish (Paralichthys dentatus, P. lethostigma and Ancylopsetta quadrocellata) (Figure 1). Cons ide ring that information on numerous species is presented in this paper, it is obvious that a detailed account cannot be given on each; however, further information is available in the bibliography. This paper is meant to be an introductory presentation to the layman who desires to work with one or more phases of the life cycle of the flatfish, and should serve as an introduction to the literature and culture techniques for interested scientists. An annotated bibliography bas been prepared by us to provide additional reference material (White and Stickney, 1973). CULTURE FACILITIES AT SKIDAWAY INSTITUTE OF OCEANOGRAPHY A flow through water system is utilized in our culture system. Water is taken from the Skidaway River, passed through a gravel filter, secondarily 2 filtered through sand swimming pool pressure filters (Figure 2), and UV steri­ lized water is then heated to desired temperature by a fuel oil heater equipped with a stainless steel heat exchanger. Prior to the 1973 experiments the secondary filter and UV systems had not been installed and bacterial disease problems wer e encountered. These problems have largely been avoided since the system was modified. A detailed description of the water system and culture building is presented in a technical report by White, ~ al. (1973). Postlarval flounder are reared after capture in 50 l fiberglass culture tanks which are placed in water tables for temperature control (Figure 3). The water is static within these tanks where the fish remain until they reach between 0. 1 to 1. 0 g. The water tables can be accurately maintained at a desired temperature by adjusting a series of valves which mix ambient and heated salt water and allow it to flow around the culture tanks. The large reservoir of heated water within the water tables also serves to reduce heat loss from the culture tanks during power failures or shutdowns of the water supply system for maintenance or repair. One meter diameter fiberglass tanks, each supplied with running water and equipped with a Venturi drain system are used for fish once they outgrow the aquarium sized tanks (Figure 4 ). During the design phase a recirculating system was considered as a possibility but abandoned in favor of the flow-through system presently in use. Several reasons were involved in that dec is ion. 1) A recirculating system requires a biological filter to remove waste products from the water, and while such filters have been designed and used in freshwater systems with varying degrees of sue cess, the technology of biological 3 filters in conjunction with marine systems is generally lacking. After some experience with biofilters we realized that inordinate amounts of time and effort could be spent in developing and maintaining these filters. 2) A biological filter was deemed impractical since running several experiments simultaneously would require an individual filter for each experiment and treat- ment. For systems where the mixing of effluents would not create problems a closed or semi-closed system might be more practical. 3) Experiments testing various environmental parameters such as salinity and temperature would be difficult in a closed system because of mixing of treatment waters in reservoirs and filters. In practice only one treatment could be run at a time. This is neither temporally or scientifically desirable. 4) Because of the clay turbidity, included organic matter and bacteria asso­ ciated with raw Skidaway River water ,an elaborate filter system would be required even in a closed system since makeup water must be available on demand. BASIC CULTURE TECHNIQUES The pleuronectiform fishes generally have small pelagic (floating) eggs which follow normal symmetrical tEieostdevelopment through the early larval stages (Norman, 1934). Pearcy (1962) discussed other flatfish with demersal (sinking) eggs. At a late stage of development, metamorphosis, the characteristic