Study on sperm cryopreservation for paternal germplasm repository of selected indigenous fishes in Taiwan

Abstract

This study aimed to investigate the biological characteristics and to establish the related cryopreservation protocol of sperm of selected indigenous freshwater fishes - Onychostoma barbatulus, Candidia barbata, Distoechodon tumirostris and Acrossocheilus paradoxus in Taiwan. The enhanced cryoprotectants were progressively studied using basic dimethyl sulfoxide (DMSO) with optional addition of 0.03, 0.06, 0.09 or 0.12 M sucrose or trehalose, and further addition of CAPS (3-Cyclohexylamino-1- propanesulfonic acid), TAPS (tris-hydroxymethyl methylamino-propane sulfonic acid) or milk. Milt mixture with various cryoprotectant combinations were frozen using freezing laboratory-designed protocols FW1, FW2, or FW3. Results indicated that 10 to 15% DMSO were favorable for four experimental fishes and trehalose was better than sucrose with overall optimal concentration of 0.06 M. Addition of TAPS was found favorable for milt of S. barbatulus and C. barbata while CAPS was suitable for D. tumirostris and A. paradoxus. There was obvious species-specific preference of enhanced cryoprotectant and freezing protocol in each species. The optimal combination of enhanced cryoprotectant and freezing protocol for respective species were further studied. Using the optimal enhanced cyoprotectant combinations and freezing protocol, 0.5-m1 straws containing cryopreserved sperm of these fishes have been stored in liquid nitrogen at -196°C as an example of paternal germplasm repository and related databank. Abstract: Taiwan is surrounded by an ocean and a strait and located in the subtropical and tropical climate zones. Optimal climate, suitable water and soil quality, and diligent aquafarmers provided Taiwanese aquacul-turists with a wealth of valuable experiences gained from aquaculture practices for over 300 years. From 1960 to 1980, aquaculture production started to rise during its prosperous phase. It was followed by a transitional phase, where several major problems occurred, including overexploitation of aquafarms, saltwater intrusion in nearby agricultural lands, land subsidence, damage of the coastal landscape, and outbreaks of fish diseases. In addition, the government put inappropriate or incorrect policies into place that slowed down the progress of aquaculture development. In contrast, world aquaculture has increasingly developed in most aquaculture-producing countries. Its tremendous importance has become even more evident during recent decades. These developments are in response to (a) decreasing fisheries resources due to overfishing, (b) growing problems of pollution in marine and freshwater environments, (c) increasing human population and thus an increasing demand for protein from aquaculture for food, and (d) exploring the potential of aquatic organisms as indicators of healthy food and for biomedical purposes. In this paper, technical and nontechnical strategies for the future development of Taiwanese aquaculture are discussed, with the goal of bringing about another transitional and outreach phase. The prospects and visions for sustainability of the industry are summarized. The past and current status of Taiwanese aquaculture may thereby serve as a lesson for other countries in which the aquaculture industry is still developing or at its peak.