The Determination of Mass Marking Methods with High Marks Retention Rate for Hatchery-reared Fry

Abstract

In recent years, because of the coastal fishery resource decline, the hatchery-reared fry of both black porgy (Acanthopagrus schlegeli) and giant sea perch (Lates japonicus) were commonly mass released to the surrounding waters in Taiwan. Even though the releasing programs were in process for many years in Taiwan, the releasing effects were not often assessed. Therefore, it is necessary to examine several suitable mass marking methods with a high marks retention rate, an operations time saving, an avoidance of stress due to handling, an inexpensive and labor saving process, for the fry in order to assess the effects of releasing programs. In order to study the mark retention rates and survival rates of three marking treatments, i.e., immersing fish bodily into a water solution containing comestible pigment with a dye for the body surface (MD), immersing the fish into a water solution containing tetracycline to mark calcified hard tissue (MI), spraying harmless pigment with fluorescent material to mark the skin (MS) and the control, two species of black porgy and giant sea perch were examined respectively, from June to October, 2004. In addition, a double marking method, i.e., spraying harmless pigment with fluorescence to mark skin (MS) after feeding fish mash containing tetracycline to mark calcified hard tissue (MF) for two weeks, was examined if it could increase marks retention rate for giant sea perch in November, 2004. Based on the comparisons of mark retention rates and survival rates, MI is, MS may be, and MD is not a suitable method for black porgy. Both MI and MS are suitable methods while MD is not a suitable method for giant sea perch. The double marking method of combining MS and MF is good and suitable for giant sea perch. Both MS and MF also have lower costs and more individuals can be marked.