| Bottom trawl fisheries in West Africa is an important part of Shanghai oversea fisheries,which is the main perpetrators of Shanghai’s agriculture "going out" strategy. At present, shanghai’s bottom trawl fisheries in west Africa has had 40 trawlers vessels,which the annual output is about 7,000 tons, the distribution of fishing ground in Mauritania and Morocco, and its targeting fish is cuttlefish and octopus which have the high economic value. As the West African coastal countries manage the fishing vessels increasingly stringent and fuel costs increase, during the effective operating time how to improve the efficiency of fishing and fishing production is the main problem currently faced by bottom trawl fisheries in West Africa. In this study, based on the fishing statistical data of bottom trawlers from Shanghai distant-water fishery company during 2010 to 2015 in Mauritania, and the fishing statistical data of bottom trawlers during 2012 to 2015 in Morocco, combined with the satellite remote sensing data such as sea surface temperature(SST) and sea surface height anomaly(SSHA), the method of habitat suitability index, method of frequency analysis and fisheries center of gravity were used to investigate the fishing ground of Mauritania and Morocco bottom trawl fishery. The results from this study are as follows:(1)In this study, based on production statistics fished by bottom trawlers from Shanghai fisheries company in Mauritania sea during 2010 to 2015, the spatial-temporal distribution of fishing ground for bottom trawling fishery is studied by the method of frequency analysis and fisheries center of gravity. The studies suggest that the distribution of bottom trawling fishery is located in the waters of 16.90 °-17.70 ° W and 19.70 ° N- 20.80 ° N in Mauritania, mainly concentrated in the 17.40 °-17.60 ° W and 20.20 °-20.70 ° N. The monthly catch ranged from 27 to 77 kg per fishing net, the average catch attained 43.98 kg per fishing net. The studies suggest that the fishing center of gravity presents the regularity of distribution, basically distributed within a latitude and longitude. The fishing center of gravity are mainly distributed in the waters of 17.38 °-17.59 ° W and 20.49 °-20.49 ° N during January and April, in the waters of 17.21 °-17.33 ° W and 20.26 °-20.26 ° N during July and August, in the waters of 17.43 °-17.54 ° W and 20.40 °-20.64°N during September and November, and in the waters near 17.08 ° W and 20.00 ° N t in December, respectively.(2)In combination with satellite remote sensing data including sea surface temperature(SST) and sea surface height anomaly(SSHA), the fishing ground distribution of bottom trawl fishery and its relationship with marine environmental factors were studied. The results suggest that the fishing ground distribution is closely related to marine environment factors such as SST, SSHA and water depth, the suitable range of marine environment factors are variable among different months. The fishing grounds is distributed in waters of SST ranging from 15 to 28 ° C, the optimum range of SST is 16-22 ° C. The fishing ground is located in the waters of SSHA with the value of- 50-10 cm, and the optimal scope of SSHA is- 20-40 cm and- 10-10 cm. The fishing ground is distributed in the waters of the depth of 10-90 m, the optimal depth for fishing ground is 50-70 m.(3)Based on the fishing data of bottom trawlers from Shanghai distant-water fishery company during 2010 to 2015, combined with the satellite remote sensing data such as sea surface temperature(SST) and sea surface height anomaly(SSHA), the method of habitat suitability index including the geometric model and arithmetic average model was used to investigate the fishing ground of Mauritania bottom trawl fishery. The results suggest that the fishing seasons are from January to April and from July to December in Mauritania bottom trawling. The monthly suitability index was established based on the relationship between fishing nets and SST, SSHA and sea depth, and there are differences among different month for appropriate scope of marine environment. For AMM model, in the fishing areas in which HSI is greater than 0.6,the percentage of fishing nets and catch attained 76.10% and 78.66% of the total, the average catch of fishing net gradually increased with the increase of HSI, from 29.37 kg/fishing net with the HIS value of 0-0.2 to 47.20 kg/fishing net with the HSI value of 0.8-1.0. For GMM model, in the fishing areas in which HSI is greater than 0.6,the percentage of fishing nets and catch attained 66.71% and 71.18% of the total, the monthly average catch of fishing net time don’t show a reasonable rule. The results indicated that AMM model is more suitable for forecasting fishing ground in Mauritania bottom trawl fishery.(4)In this study, based on production statistics fished by bottom trawlers from Shanghai fisheries company in Moroccan sea during 2012 to 2015, the spatial-temporal distribution of fishing ground for bottom trawling fishery in winter fishing season is studied by the method of frequency analysis and fisheries center of gravity. The studies suggest that the distribution of bottom trawling fishery in winter fishing season is located in the waters of 15.0°-18.0°W and 20.0°N-26.0°N in Morocco, mainly concentrated in the 15.5°-16.5°W, 17.0°-17.5°W, 17.40°-17.60°W and 21°-22°N, 23°-25°N, in which the catch occupied above 85% of the total catch. The studies suggest that the fishing center of gravity presents the regularity of distribution, basically distributed within a latitude and longitude. The fishing center of gravity are mainly distributed in the waters near 16.63°W and 23.20°N during January, in the waters near 16.53°W and 23.03°-23.09°N during December and January, in the waters near 23.21°N and 16.48°W during February, and in the waters near 23.56°N and 16.33°W in March, respcetively.(5)Based on the fishing statistical data of bottom trawlers from Shanghai distant-water fishery company during 2012 to 2015, the month is from January to March and from November to December,combined with the satellite remote sensing data such as sea surface temperature(SST), Chlorophyll-a(Chl-a) and sea surface height anomaly(SSHA), the method of habitat suitability index including the geometric model and arithmetic average model is used to study the fishing ground of Morocco bottom trawl fishery. The monthly suitability index is established based on the relationship between fishing nets and SST, SSHA, Chl-a and sea depth, and there are differences among different month for appropriate scope of marine environment. For AMM model, in the fishing areas in which HSI is greater than 0.6, the percentage of fishing nets and catch attained 65.92% and 67.57% of the total. For GMM model, in the fishing areas in which HSI is greater than 0.6, the percentage of fishing nets and catch only attained 44.78% and 49.60% of the total. The results indicated that AMM model is more suitable for forecasting fishing ground in Moroccan bottom trawl fishery. |
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