Translocation of Evechinus chloroticus in the SUR 5 Fishery and the reproductive potential of large urchins

Gonad Index;Translocation

Thomas, Samuel Frederick ; Barker, Mike

University of Otago

关键词: Gonad Index;    Translocation;   

Others  :  https://ourarchive.otago.ac.nz/bitstream/10523/1830/1/ThomasSamuel2011MSc.pdf

美国|英语

来源: Otago University Research Archive

【 摘 要 】

Evechinus chloroticus (commonly known as Kina) is a commercially important species found in coastal New Zealand waters. Their gonad quality is, however, poor in many regions and thus the areas with high quality gonads tend to be overfished. Feeding E. chloroticus on enhanced food diets is a common method to improve the roe quality but limited success has been achieved in improving the gonad quality to acceptable market standards. Translocation of E. chloroticus in the wild as a method for commercial gonad enhancement is examined in this thesis within the South Coast urchin fishing area (SUR5) to assess if gonad quality could be improved. Approximately 1000kgs of urchins were translocated from an area with poor quality gonad and high urchin population densities (Passage Island) to an area of high gonad quality and low urchin population densities (Sealers Bay) in Chalky Inlet a commercially fished area. The urchins were left for five months and sampled three times within this period. Changes in gonad index (GI) were measured to assess whether translocating E. chloroticus can be effective. Significant differences occurred after the translocations with increased gonad growth in both the translocated samples compared to the Passage Island samples which had lower gonad indices. There were also differences in gonad index over the five month study length as a result of spawning before the last sample was taken, which resulted in significant changes in gonad index. Aristotle’s lantern index increased in two translocated samples over the five month period. Evechinus chloroticus fished from the Southern Coast SUR5 fishing area are of a large test diameter (TD) >120mm. Questions have been raised about the reproductive potential of these large urchins, thus the opportunity was taken to test whether these large urchins were reproductively senile in the SUR5 fishery and if they do produce viable gametes would their larvae develop normally. Six large urchins >150mm TD were spawned and the fertilization rates were measured, with the embryos then cultured through to an 8 arm larval stage. Postoral arm length was measured over the larvae development to assess whether normal development occurred. Fertilization success in the large urchins was high (99-100%) in all replicate samples. Larvae development was normal with increasing postoral arm length (µm) over the culture period, and no abnormal larvae were observed. Translocation of E. chloroticus would provide an effective method of gonad enhancement over a short time frame (five months) that could be more cost effective than intensive enhanced feeding methods in improving gonad for commercial sale. Large E. chloroticus >150mm TD, produce viable gametes and larvae that contribute to the larval pool and therefore could be a residual breeding stock in overfished areas around the coast.