| Constructing artificial reef is an important measure to restore Marine habitat and conserve fishery resources.The construction of artificial reef is a systematic project.As the foundation of Marine pasture,the production of reef is an important content.The optimization design of reef can not only improve the trapping effect of reef on fish,but also effectively reduce the production cost.As one of the main breeding and releasing species in Marine pasture area,black sea bream is the main releasing object in coastal provinces and cities of South China Sea.In the early stage after release,released fish fry are weak in foraging and avoiding enemy pests,while artificial reef can provide shelter for these released fish and form a buffer area,which improves the survival rate of released fish fry to a certain extent.In this study,black sea bream was taken as the experimental object to explore the attracting effect of typical artificial reef structures on black sea bream.In the experiment of attracting effect of reef vertical plate with different hole aperture and hole shape on young black snapper,the results showed that the input reef vertical plate all had certain attracting effect on young black snapper.In the experiment of setting different hole sizes,the vertical version B1 with square hole size of 8cm has the best fish collecting effect(average occurrence rate is 9.89%).It is followed by reef riser B3 with an opening hole of 24 cm,reef riser B2 with an opening hole of 16 cm,reef riser B5 with an opening hole of 40 cm,reef riser B4 with an opening hole of 32 cm,The aperture of vertical reef B1,B2,B3,B4 and B5 correspond to 2,4,6,8 and 10 times of the body height(stretching fins)of juvenile black snapper,respectively.The results showed that the young black sea bream tended to prefer the reef riser which had little difference between the diameter side length and the body height of the young black sea bream.Five different opening shapes(square,triangle,circle,vertical rectangle and horizontal rectangle)were designed to attract juvenile black snapper.The results showed that under small aperture(8-24cm),different opening shapes of reef vertical plate had no significant difference in attracting effect on juvenile black snapper(P>0.05).When the reef riser aperture was 32 cm,there was a significant difference in frequency between the reef riser with square holes and the reef riser with horizontal rectangular holes(P<0.05).The reef riser with square holes showed the lowest frequency of occurrence,but when the reef riser aperture was 40 cm,the reef riser with different shapes showed the lowest frequency of occurrence.There was no significant difference in the average occurrence rate of young black snapper.This may be due to the fact that,under the condition of large aperture,vertical plate has the smallest surface area and the shortest distance from aperture edge to reef edge,which has less blocking sight for young black snapper and the least shadow area formed under natural light.In tests with different spacing and shading of reef bulkheads,spacing of bulkheads with different gradients was designed: H1 group of 8cm,H2 group of 16 cm,H3 group of 24 cm,H4 group of 32 cm and H group of 40 cm,and hollow partitions of different shadow ratio group G1,G2,G3,G4 and G5.The shadow ratios(the ratio of the area occupied by the solid part of the front reef bulkhead to the whole reef area)were33.55%,37.92%,42.20%,46.55% and 50.86%,respectively,and their trapping effects on young black snapper were observed.The results showed that when the solid separator was set at 8 cm(H1)height,the trapping effect of juvenile black sea bream was the best,which was 16.83 %,which was twice the height of juvenile black sea bream.In the reef shadow effect test,the shadow group represented by group G1(the reef partition plate was two hollow strips)had the highest trapping effect on juvenile black bream(12.08 %),while the group G2 – G5 showed an increasing trend,and the occurrence rate of test fish in group G5 was 10.91 %. |
