CEPHALOPOD FISHERY FORECASTING METHOD IN NORTHWEST AFRICAN WATERS BASED ON ENVIRONMENTAL FACTORS

Abstract

A cephalopod fishery forecasting method in northwest African waters based on environmental factors, including the following steps: step 1: acquiring catch production statistical data from cephalopod fisheries in northwest African waters of many years; step 2: acquiring marine environmental data corresponding to the catch production statistical data, the marine environmental data including sea surface temperature (SST) and sea surface height anomaly (SSHA); step 3: studying the relationship between the operating haul, the operating output ratio and the average output per haul in each interval as indexes of a central fishery and the marine environmental data of step 2; and step 4: establishing suitability indexes (SI) of different environmental factors, and calculating habitat suitability indexes (HSI) under different weight cases by using an expert assignment method, thus obtaining distribution waters of the central fishery of cephalopod fisheries in northwest African waters for forecasting the central fishery.

Claims

1. A cephalopod fishery forecasting method in northwest African waters based on environmental factors, comprising the following steps: step 1: acquiring catch production statistical data from cephalopod fisheries in northwest African waters of a plurality of years, the catch production statistical data including an operating time, an operating sea depth, an operating haul and a total catch output; step 2: acquiring marine environmental data corresponding to the catch production statistical data, the marine environmental data including a sea surface temperature (SST) and a sea surface height anomaly (SSHA), based on a monthly time resolution and a 0.50.5 spatial resolution; step 3: studying a relationship between the operating haul, the operating output ratio and an average output per haul in each interval as indexes of a central fishery and the marine environmental data of the step 2; and step 4: establishing a suitability indexes (SI) of different environmental factors, calculating habitat suitability indexes (HSI) under different weight cases by using an expert assignment method, and obtaining distribution waters of the central fishery of cephalopod fisheries in northwest African waters, and obtaining an optimal weight case in the distribution waters for forecasting the central fishery.

2. The cephalopod fishery forecasting method in northwest African waters based on environmental factors according to claim 1, wherein the catch production statistical data from the cephalopod fisheries in northwest African waters is data of 4-6 years.

3. The cephalopod fishery forecasting method in northwest African waters based on environmental factors according to claim 1, wherein for Moroccan fisheries in the northwest Africa, marine environmental data corresponding to the catch production statistical data is acquired, the marine environmental data includes the sea surface temperature (SST), the sea surface height anomaly (SSHA) and a chlorophyll concentration Chl-a; the operating haul, the operating output ratio and the average output per haul in each interval are calculated using 1 C. as an interval of the SST, and then an optimal SST range of the central fishery is obtained; the operating haul, the operating output ratio and the average output per haul in each interval are calculated using 10 cm as an interval of the SSHA, and then an optimal SSHA range of the central fishery is obtained; the operating haul, the operating output ratio and the average output per haul in each interval are calculated using 0.01-1.0, 1.0-2.0, 2.0-5.0, 5.0-20.0 or 20.0-50.0 mg/m.sup.3 as an interval of Chl-a content, and then an optimal Chl-a range of the central fishery is obtained; and the operating haul, the operating output ratio and the average output per haul in each interval are calculated using 10 m as an interval of sea depth, and then an optimal sea depth range of the central fishery is obtained.

4. The cephalopod fishery forecasting method in northwest African waters based on environmental factors according to claim 3, wherein the suitability indexes (SI) of different environmental factors are established for the marine environmental data including the sea surface temperature (SST), the sea surface height anomaly (SSHA) and the chlorophyll concentration Chl-a, and the habitat suitability indexes HSI under different weight cases are calculated using the following formula:
HSI=X.sub.SST*I.sub.SI_SST+X.sub.SSHA*I.sub.SI_SSHA+X.sub.CHL-a*I.sub.SI-CHL-a+X.sub.DEPTH*I.sub.SI_DEPTH; wherein, I.sub.SI_SST indicates a suitability index based on the sea surface temperature; I.sub.SI_SSHA indicates a suitability index based on the sea surface height anomaly; I.sub.SI-CHL-a indicates a suitability index based on the chlorophyll concentration; I.sub.SI_DEPTH indicates a suitability index based on the sea depth; and X.sub.SST, X.sub.SSHA, X.sub.CHL-a and X.sub.DEPTH indicate weight values of the sea surface temperature, the sea surface height anomaly, the chlorophyll concentration and the sea depth respectively.

5. The cephalopod fishery forecasting method in northwest African waters based on environmental factors according to claim 4, wherein waters with a highest operating haul are set as waters with a highest distribution probability of the central fishery, and the suitability index SI is assigned with 1; when there is no operating haul, the suitability index SI is assigned with 0; when the operating haul is higher than the average, the suitability index SI is assigned with 0.5; and when the operating haul is lower than the average, the suitability index SI is assigned with 0.1.

6. The cephalopod fishery forecasting method in northwest African waters based on environmental factors according to claim 4, wherein the following five weight cases are used for the weight values of the sea surface temperature, the sea surface height anomaly, the chlorophyll concentration and the sea depth: Case 1: X.sub.SST is 0.25, X.sub.SSHA is 0.25, X.sub.CHL-a is 0.25, and X.sub.DEPTH is 0.25; Case 2: X.sub.SST is 0, X.sub.SSHA is 0.9, X.sub.CHL-a is 0, and X.sub.DEPTH is 0.1; Case 3: X.sub.SST is 0.1, X.sub.SSHA is 0.1, X.sub.CHL-a is 0, and X.sub.DEPTH is 0.8; Case 4: X.sub.SST is 0.9, X.sub.SSHA is 0.1, X.sub.CHL-a is 0, and X.sub.DEPTH is 0; Case 5: X.sub.SST is 0.4, X.sub.SSHA is 0.4, X.sub.CHL-a is 0.1, and X.sub.DEPTH is 0.1; an optimal weight case for forecasting the central fishery of the Moroccan cephalopod fisheries is obtained by comparing the HSI values in the five different weight cases with a set threshold respectively.

7. The cephalopod fishery forecasting method in northwest African waters based on environmental factors according to claim 1, wherein statistics on monthly total catch haul, total output and days are collected for Mauritania fisheries in the northwest Africa based on SST minimum 15 C., SSHA minimum 45 cm, sea depth minimum 15 m and corresponding intervals 1 C., 10 cm and 10 m, then a catch haul ratio, an output ratio and an average output per haul at intervals of SST 1 C., SSHA 10 cm and sea depth 10 m are solved, and an optimal sea surface temperature interval, an optimal sea surface height anomaly interval and an optimal sea depth interval of the central fishery in each month are thus obtained.

8. The cephalopod fishery forecasting method in northwest African waters based on environmental factors according to claim 7, wherein the habitat suitability indexes (HSI) under different weight cases are calculated for the corresponding marine environmental data by adopting the following formula:
HSI=X.sub.SST*I.sub.SI_SST+X.sub.SSHA*I.sub.SI_SSHA+X.sub.DEPTH*I.sub.SI_DEPTH; wherein, I.sub.SI_SST indicates a suitability index based on the sea surface temperature; I.sub.SI_SSHA indicates a suitability index based on the sea surface height anomaly; I.sub.SI_DEPTH indicates a suitability index based on the sea depth; X.sub.SST, X.sub.SSHA and X.sub.DEPTH indicate weight values of the sea surface temperature, the sea surface height anomaly and the sea depth respectively.

9. The cephalopod fishery forecasting method in northwest African waters based on environmental factors according to claim 8, wherein based on a frequency distribution map of the operating haul, the suitability indexes SI of different environmental factors are established, the values of the suitability indexes SI are assigned using an expert assignment method, the maximum operating haul NETmax is set in waters with a highest catch distribution probability, and the suitability index SI is assigned with 1; when there is no operating haul, the suitability index SI is assigned with 0; when the operating haul is higher than the average, the suitability index SI is assigned with 0.5; and when the operating haul is lower than the average, the suitability index SI is assigned with 0.1.

10. The cephalopod fishery forecasting method in northwest African waters based on environmental factors according to claim 8, wherein the following five weight cases are used for the weight values of the sea surface temperature, the sea surface height anomaly and the sea depth: Case 1: X.sub.SST is 0.6, X.sub.SSHA is 0.3, and X.sub.DEPTH is 0.1; Case 2: X.sub.SST is 0.5, X.sub.SSHA is 0.2, and X.sub.DEPTH is 0.3; Case 3: X.sub.SST is 0.4, X.sub.SSHA is 0.2, and X.sub.DEPTH is 0.4; Case 4: X.sub.SST is 0.3, X.sub.SSHA is 0.4, and X.sub.DEPTH is 0.3; Case 5: X.sub.SST is , X.sub.SSHA is , and X.sub.DEPTH is ; an optimal weight case for forecasting the central fishery is obtained by comparing the HSI values in the five different weight cases with a set threshold respectively.

11. The cephalopod fishery forecasting method in northwest African waters based on environmental factors according to claim 3, wherein the catch production statistical data from the cephalopod fisheries in northwest African waters is data of 4-6 years.

12. The cephalopod fishery forecasting method in northwest African waters based on environmental factors according to claim 7, wherein the catch production statistical data from the cephalopod fisheries in northwest African waters is data of 4-6 years.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG. 1 is a flow diagram of a fishery forecasting method according to the present invention.

[0019] FIG. 2 is a flow diagram of a Moroccan waters cephalopod fishery forecasting method according to Embodiment 1 of the present invention.

[0020] FIG. 3 is a flow diagram of a Mauritanian waters cephalopod fishery forecasting method according to Embodiment 2 of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] The present invention is further illustrated below in combination with specific embodiments and drawings.

[0022] Cephalopods are annual species, and the fishery situation and the resource abundance thereof are closely related to the marine environment, so climate changes and different marine environments directly affect the habitat and resource abundance of the cephalopods, and then affect the fishery production and scientific management. Therefore, it is extremely important to study the main environmental factors affecting the distribution of cephalopod habitats. The use of environmental factors to establish a fishery prediction model can scientifically guide the production of cephalopods in northwest African waters, and also guides the efficient catch production of related enterprises in the waters.

Embodiment 1

[0023] For the Moroccan waters in the Atlantic Ocean, the main environmental factors affecting the distribution of cephalopod habitats are obtained by research through the following steps.

[0024] Step 101: Acquire catch production statistical data from Moroccan fisheries in 2012-2015, the catch production statistical data including operating time, longitude, latitude, sea depth, operating haul and output.

[0025] The catch production statistical data from Moroccan fisheries is from Shanghai Deep-Ocean Fishery Company.

[0026] Step 102: Acquire marine environmental data corresponding to the catch production statistical data, the marine environmental data including sea surface temperature (SST), sea surface height anomaly (SSHA) and chlorophyll concentration Chl-a, based on a monthly time resolution and a 0.50.5 spatial resolution, from January to May and from November to December in 2012-2015.

[0027] Step 103: Study the relationship between the operating haul, the operating output ratio and the average output per haul in each interval as indexes of a central fishery and the SST, SSHA, Chl-a and sea depth.

1) Calculate the operating haul, the operating output ratio and the average output per haul in each interval of 1 C. of SST to obtain an optimal SST range of the central fishery;
2) Calculate the operating haul, the operating output ratio and the average output per haul in each interval of 10 cm of SSHA to obtain an optimal SSHA range of the central fishery;
3) Calculate the operating haul, the operating output ratio and the average output per haul in each interval of 0.01-1.0, 1.0-2.0, 2.0-5.0, 5.0-20.0 or 20.0-50.0 mg/m.sup.3 of Chl-a content to obtain an optimal Chl-a range of the central fishery;
4) Calculate the operating haul, the operating output ratio and the average output per haul in each interval of 10 cm of sea depth to obtain an optimal sea depth range of the central fishery.

[0028] Step 104: Establish suitability indexes SI of different environmental factors, assign values to the suitability indexes SI by using an expert assignment method, and set waters having the highest distribution probability of the central fishery as waters with the maximum operating haul, the suitability index SI of which is assigned with 1; when there is no operating haul, assign the suitability index SI with 0; when the operating haul is higher than the average, assign the suitability index SI with 0.5; and when the operating haul is lower than the average, assign the suitability index SI with 0.1.

[0029] The fishing vessel generally determines a fishery based on the experience of a captain and the images of a fish finder. Therefore, the operating haul can be regarded as an indicator of discovering fish, and is used to indicate the suitability index of a habitat.

TABLE-US-00001 TABLE 1 Determination criteria for habitat suitability index Number Suitability index value Description of habitat use 1 1.0 Waters having the highest 2 0.5 operating haul 3 0.1 Waters having the operating haul 4 0.0 above the average Waters having the operating haul below the average Waters having 0 operating haul

[0030] Step 105: Calculate habitat suitability indexes HSI under five different weight cases by using the following formula:

HSI=X.sub.SST*I.sub.SI_SST+X.sub.SSHA*I.sub.SI_SSHA+X.sub.CHL-a*I.sub.SI-CHL-a+X.sub.DEPTH*I.sub.SI_DEPTH

[0031] Calculate the changes of habitat suitability indexes (HSI) from 0 to 1 under different weights of relevant marine environmental factors. The area where the HSI is more than 0.6 is generally regarded as the waters where the central fishery is distributed.

[0032] In the formula: I.sub.SI_SST, I.sub.SI_SSHA, I.sub.SI-CHL-a and I.sub.SI_DEPTH are respectively suitability indexes based on sea surface temperature, sea surface height anomaly, chlorophyll concentration and sea depth. X.sub.SST, X.sub.SSHA, X.sub.CHL-a and X.sub.DEPTH are weight values of sea surface temperature, sea surface height anomaly, chlorophyll concentration and sea depth. Totally five different cases of different weights are provided, as shown in Table 2 below.

TABLE-US-00002 TABLE 2 Weight values based on different environmental factors related to the central fishery Case SST SSHA CHL-a DEPTH 1 0.25 0.25 0.25 0.25 2 0 0.9 0 0.1 3 0.1 0.1 0 0.8 4 0.9 0.1 0 0 5 0.4 0.4 0.1 0.1

[0033] The HSI values in the five different weight cases are compared with a set threshold respectively to obtain an optimal weight case for forecasting the central fishery of Moroccan cephalopod fisheries. Different weight cases are compared using the statistical data from January to March and from November to December in 2012-2015, the HSI values being 0-0.2, 0.2-0.4, 0.4-0.6, 0.6-0.8, and 0.8-1.0. On this basis, statistical analysis is performed on the HSI value >0.6 and the HSI value <0.4 in the five different weight cases to obtain an optimal weight case for forecasting the central fishery.

[0034] According to the above method, the following analysis is based on specific statistical data:

1. Analysis of Production Status

1) Relationship Between Fishery Distribution and Sea Surface Temperature (SST)

[0035] The analysis results show that the distribution of cephalopod fisheries is closely related to the sea surface temperature, and different months have different suitable SST ranges. In January, the operation is mainly in the waters having the SST range of 1619 C., the suitable SST range for high average output per haul is 16-17 C. and 18-19 C., and the average output is 130-153 kg. In February, the operation is mainly in the waters having the SST range of 1519 C., the suitable SST range for high average output per haul is 1617 C. and 1819 C., and the average output is 122147 kg. In March, the operation is mainly in the waters having the SST range of 1517 C., the suitable SST range for high average output per haul is 1516 C., and the average output is 89.16 kg. In November, the operation is mainly in the waters having the SST range of 1823 C., the suitable SST range for high average output per haul is 1923 C., and the average output is 162185 kg. In December, the operation is mainly in the waters having the SST range of 1621 C., the suitable SST range for high average output per haul is 2021 C., and the average output is 457 kg.

2) Relationship Between Fishery Distribution and SSHA

[0036] The analysis results show that the distribution of cephalopod fisheries is closely related to the sea surface height anomaly, and different months have different suitable SSHA ranges. In January, the operation is mainly in the waters having the SSHA range of 6020 cm, the suitable SSHA range for high average output per haul is 6030 cm, and the average output is 124185 kg. In February, the operation is mainly in the waters having the SSHA range of 6030 cm, the suitable SSHA range for high average output per haul is 6040 cm, and the average output is 123137 kg. In March, the operation is mainly in the waters having the SSHA range of 6030 cm, the suitable SSHA range for high average output per haul is 6040 cm, and the average output is 96101 kg. In November, the operation is mainly in the waters having the SSHA range of 5010 cm, the suitable SSHA range for high average output per haul is 4030 and 100 cm, and the average output is 189209 kg. In December, the operation is mainly in the waters having the SSHA range of 5010 cm, the suitable SSHA range for high average output per haul is 5040 cm, and the average output is 558.69 kg.

3) Relationship Between Fishery Distribution and Chlorophyll Concentration

[0037] The analysis results show that the distribution of cephalopod fisheries is closely related to the chlorophyll concentration, and different months have different suitable chlorophyll concentration ranges. In January, the operation is mainly in the waters having the Chl-a range of 0.0150 mg/m.sup.3, the suitable Chl-a range for high average output per haul is 1.05.0 mg/m.sup.3, and the average output is 96127 kg. In February, the operation is mainly in the waters having the Chl-a range of 0.0120 mg/m.sup.3, the suitable Chl-a range for high average output per haul is 1.020.0 mg/m.sup.3, and the average output is 119128 kg. In March, the operation is mainly in the waters having the Chl-a range of 0.0150 mg/m.sup.3, the suitable Chl-a range for high average output per haul is 1.02.0 and 5.050 mg/m.sup.3, and the average output is 99110 kg. In November, the operation is mainly in the waters having the Chl-a range of 0.0120 mg/m.sup.3, the suitable Chl-a range for high average output per haul is 0.015.0 mg/m.sup.3, and the average output is 169176 kg. In December, the operation is mainly in the waters having the Chl-a range of 0.0150 mg/m.sup.3, the suitable Chl-a range for high average output per haul is 2.05.0 mg/m.sup.3, and the average output is 256.24 kg.

4) Relationship Between Fishery Distribution and Sea Depth

[0038] The analysis results show that the distribution of cephalopod fisheries is closely related to the sea depth, and different months have different suitable sea depth ranges. In January, the operation is mainly in the waters having the sea depth range of 2090 m, the suitable sea depth range for high average output per haul is 2040 m, and the average output is 131140 kg. In February, the operation is mainly in the waters having the sea depth range of 20100 m, the suitable sea depth range for high average output per haul is 2050 m and 6070 m, and the average output is 117141 kg. In March, the operation is mainly in the waters having the sea depth range of 2080 m, the suitable sea depth range for high average output per haul is 7080 m, and the average output is 169 kg. In November, the operation is mainly in the waters having the sea depth range of 3080 m, the suitable sea depth range for high average output per haul is 3040 m, and the average output is 246.49 kg. In December, the operation is mainly in the waters having the sea depth range of 2080 m, the suitable sea depth range for high average output per haul is 2050 m, and the average output is 217283 kg.

2. Suitability Index (SI) Establishment

[0039] Suitability indexes (Table 3) based on SST, SSHA, Chl-a and seabed sea depth in each month are respectively established according to Table 1. According to Table 3, the SST, SSHA, Chl-a and sea depth for highest SI in January are respectively 1718 C., 5040 cm, 2.05.0 mg/m.sup.3 and 3040 m; the SST, SSHA, Chl-a and sea depth for highest SI in February are respectively 1617 C., 5040 cm, 2.035.0 mg/m.sup.3 and 3040 m; the SST, SSHA, Chl-a and sea depth for highest SI in March are respectively 1617 C., 5040 cm, 2.05.0 mg/m.sup.3 and 2030 m; the SST, SSHA, Chl-a and sea depth for highest SI in November are respectively 1920 C., 010 cm, 0.011.0 mg/m.sup.3 and 6070 m; and the SST, SSHA, Chl-a and sea depth for highest SI in December are respectively 1819 C., 4030 cm, 2.05.0 mg/m.sup.3 and 6070 m. The optimal SST, SSHA, Chl-a and sea depth vary from month to month.

TABLE-US-00003 TABLE 3 Suitability indexes based on SST, SSHA, Chl-a and seabed sea depth in each month Chl- Month SI SST/ C. SSHA/cm a/(mg/m.sup.3) Sea depth/m January 1.0 17~18 50~40 2.0~5.0 30~40 0.5 16~17 30~20 1.0~2.0 60~70 0.1 18~19 60~50, 0.01~1.0, 20~30, 80~90 0.0 <16, 40~30 5.0~50 <20, >19 <60, <0.01, 40~60, >20 >50 70~80, >90 February 1.0 16~17 50~40 2.0~5.0 30~40 0.5 15~16 40~30 1.0~2.0 60~70 0.1 18~19 60~50 0.01~1.0, 20~30, 40~60, 0.0 <15, <60, 5.0~20 70~100 17~18, >30 <0.01, <20, >19 >20 >100 March 1.0 16.20~16.39 50~40 2.0~5.0 20~30 0.5 16.00~16.19 60~50 0.01~1.0 30~40 0.1 15.00~15.39 40~30 1.0~2.0, 40~80 0.0 <15, <60, 5.0~50 <20, 15.40~15.99, >30 <0.01, >80 >16.40 >50 November 1.0 19~20 0~10 0.01~1.0 60~70 0.5 20~22 40~30 1.0~2.0 30~40 0.1 18~19, 50~40, 2.0~20 40~60, 22~23 30~20, 70~80 0.0 <18, 10~0 <0.01, <30, >23 <50, >20 >80 20~10, >10 December 1.0 18~19 40~30 2.0~5.0 60~70 0.5 19~20 30~20, 1.0~2.0 20~40 0~10 0.1 16~18, 50~40, 0.01~1.0, 40~60, 20~21 10~0 70~80 0.0 <16, <50, 5.0~50 <20, >21 20~10, <0.01, >80 >10 >50

3. Comparison of Weight Cases Based on Correlation Factors of Habitat Suitability Indexes (HSI)

[0040] Through the habitat suitability indexes of the weight values set based on different environmental factors related to the central fishery (Table 3), the haul ratio, output ratio and average output per haul from January to March and from November to December in 2012-2015 are summarized according to different HSIs to obtain averages of the five cases (Table 4).

[0041] It can be seen from Table 4 that among the five cases, the haul ratio and the output ratio of Case 3 are smallest, respectively 42.97% and 38.53%, and the average output per haul is only 130.17 kg compared with other cases. Therefore, the weight setting of Case 3 is worst. The values obtained in Case 2 and Case 4 are similar and lower than Case 1 and Case 5 (Table 4), so Case 2 and Case 4 are also inferior. In Case 1 and Case 5, the haul ratio and the output ratio in which the HSI is more than 0.6 are relatively close, respectively 59.69% and 60.2% in Case 1, and 58.38% and 60.96% in Case 5. However, it can be discovered by comparison in Table 5 that Case 5 has better average output per haul and haul and output ratios in which the HSI is more than 0.8 than Case 1, so the weight setting in Case 5 is optimal.

TABLE-US-00004 TABLE 4 Average of monthly haul ratio, output ratio and average output per haul in five cases Case 1 Case 2 Average Average Case 3 Haul Output output per Haul Output output per Haul Output HSI ratio/% ratio/% haul/kg ratio/% ratio/% haul/kg ratio/% ratio/% 0.8~ 14.9 13.5 131. 49.8 52.1 151. 35.9 30.3 1.0 4 6 79 5 0 76 2 6 0.6~ 44.7 46.6 151. 0 0 0 7.05 8.17 0.8 5 4 32 25.9 23.8 133. 22.2 28.3 0.4~ 22.2 22.1 144. 0 3 57 9 2 0.6 9 3 14 0 0 0 16.8 15.7 0.2~ 2.31 2.65 166. 13.5 13.5 145. 9 3 0.4 0.47 0.67 13 2 7 77 7.11 6.92 0.0~ 205. 0.2 38 Case 3 Case 4 Case 5 Average Average Average output per Haul Output output per Haul Output output per HSI haul/kg ratio/% ratio/% haul/kg ratio/% ratio/% haul/kg 0.8~ 122. 51.5 45.7 128. 29.9 27.7 134. 1.0 70 1 2 87 3 7 71 0.6~ 168. 0 0 0 28.4 33.1 169. 0.8 20 29.0 36.1 180. 5 9 36 0.4~ 184. 5 7 82 20.8 17.4 121. 0.6 47 0 0 0 7 2 25 0.2~ 135. 8.83 7.69 126. 4.92 5.84 172. 0.4 23 43 0.59 1.42 33 0.0~ 141. 347. 0.2 32 60

[0042] Moroccan cephalopod habitat models under different weights were studied according to the production statistical data of a deep-ocean fishing company in Shanghai from 2012 to 2015 in combination with sea surface temperature (SST), sea surface height anomaly (SSHA), chlorophyll mass concentration (CHL-a) and sea depth data.

[0043] The studies show that the distribution of Moroccan cephalopod habitats is closely related to the environmental factors such as sea surface temperature, sea surface height anomaly and sea depth, and the monthly suitable environmental factors are different; the SST range in the fishery distribution area is 1523 C., the SSHA range is 6010 cm, the chlorophyll concentration is 050 mg/m.sup.3, and the sea depth range is 20100 m, wherein the most suitable SST is 1618 and 1920 C., the most suitable SSHA is 5030 cm, the most suitable chlorophyll content is 1.05.0 mg/m.sup.3, and the most suitable sea depth is 3040 and 6070 m. According to the model analysis, the weights of Case 5 are optimal, and the weight factors of SST, SSHA, CHL-a and sea depth are respectively 0.4, 0.4, 0.1 and 0.1, indicating that SST and SSHA have the greatest influence in the habitat index model, followed by sea depth, then chlorophyll.

Embodiment 2

[0044] As shown in FIG. 3, the present embodiment provides a Mauritanian cephalopod fishery forecasting method based on habitat indexes, including the following steps:

[0045] Step 101: acquire catch production statistical data from Mauritanian fisheries in 2010-2015, the catch production statistical data including operating time, operating sea depth, haul and total catch output.

[0046] The catch production statistical data is from a deep-ocean fishery company having more than 10 trawlers in 2010-2015. Since May and June are often fishing off seasons, the production statistics are from January to April and July to December every year.

[0047] Step 2: acquire marine environmental data corresponding to the catch production statistical data, the marine environmental data including sea surface temperature (SST) and sea surface height anomaly (SSHA), based on a monthly time resolution and a 0.50.5 spatial resolution, from January to April and from July to December of 2010-2015.

[0048] Step 103: collect statistics on the operating haul, the sea depth and the total catch output of different time periods in each month of 2010-2015, screen, sort and summarize the statistical data, establish a suitability index using the average output per haul as a central fishery index and using an expert assignment method, and then design different weight cases for chart calculation and comparison to obtain a spatial distribution of Mauritanian cephalopod fisheries, a relationship between the spatial distribution and the marine environment, and an optimal weight case in the corresponding waters of the Mauritanian cephalopod fisheries, wherein the relationship is the optimal SST, SSHA and sea depth range for a central fishery.

[0049] Specifically, the method includes the following steps:

1. Analysis on a Relationship Between Fishery Distribution and Environmental Factors

[0050] A frequency distribution map is drawn to understand and grasp the relationship between the production value, operating haul, average output per haul and various environmental factors, and obtain the overall environmental factors of fishery distribution in the fishing season and the optimal intervals, the maximum and minimum values of the environmental factors (sea surface temperature, sea surface height and sea depth) are found, and the fisheries are divide into intervals.

average output per haul=total output/operating haul (kg)Formula:

[0051] The relationship between the total catch haul, total catch output, average output per haul and the sea surface temperature (SST), sea surface height anomaly (SSHA), and sea depth:

[0052] Statistics on monthly total catch haul, total output and days are collected based on SST minimum 15 C., SSHA minimum 45 cm, sea depth minimum 15 m and corresponding intervals 1 C., 10 cm and 10 m, a catch haul ratio, an output ratio and an average output per haul at intervals of SST 1 C., SSHA 10 cm and sea depth 10 m are solved, and therefore an optimal sea surface temperature interval, an optimal sea surface height anomaly interval and an optimal sea depth interval of the central fishery in each month are obtained.

2. Establishment of Suitability Indexes

[0053] Based on a frequency distribution map of the operating haul, suitability indexes SI of different environmental factors are established, values of the suitability indexes SI are assigned using an expert assignment method, waters with the maximum operating haul NETmax are set as waters with the highest catch distribution probability, and the suitability index SI is assigned with 1; when there is no operating haul, the suitability index SI is assigned with 0; when the operating haul is higher than the average the suitability index SI is assigned with 0.5; and when the operating haul is lower than the average, the suitability index SI is assigned with 0.1. See Table 5:

TABLE-US-00005 TABLE 5 Determination criteria for suitability indexes Number Suitability index value Description of habitat use 1 1 Waters having the highest operating 2 0.5 haul 3 0.1 Waters having the operating haul 4 0 higher than the average Waters having the operating haul lower than the average Waters having 0 operating haul

3. Establishment of Habitat Suitability Index

[0054] HSI (Habitat suitability index) ranges from 0 to 1, based on the suitability index of each environmental factor.

TABLE-US-00006 TABLE 6 Five different weight cases Case X.sub.SST X.sub.SSHA X.sub.DEPTH 1 0.6 0.3 0.1 2 0.5 0.2 0.3 3 0.4 0.2 0.4 4 0.3 0.4 0.3 5 1/3 1/3 1/3

[0055] X.sub.sst indicates the weight of the sea surface temperature, X.sub.SSHA indicates the weight of the sea surface height anomaly; X.sub.DEPTH indicates the weight of the sea depth.

[0056] Habitat suitability indexes (HSI) are calculated under five different weight cases by using the formula HSI=X.sub.SST*I.sub.SI_SST+X.sub.SSHA*I.sub.SI_SSHA+X.sub.DEPTH*I.sub.SI_DEPTH, in which: I.sub.SST indicates a suitability index based on sea surface temperature; I.sub.SSHA indicates a suitability index based on sea surface height anomaly; I.sub.SI_DEPTH indicates a suitability index based on sea depth.

4. Comparison of Five Different Weight Cases

[0057] Different weight cases are compared using the statistical data from 2010 to January to March, July and September in 2015, the HSI values being 00.2, 0.20.4, 0.40.6, 0.60.8, and 0.81.0. On this basis, statistical analysis is performed on the HSI value >0.6 and the HSI value <0.4 in the five different weight cases to obtain an optimal weight case for forecasting the central fishery.

[0058] According to the above method, the following analysis is based on specific statistical data:

1. Analysis of Production Status

1) Relationship Between Fishery Distribution and Sea Surface Temperature

[0059] The analysis results show that the distribution of northwestern African waters cephalopod fisheries is closely related to the sea surface temperature, and different months have different suitable SST ranges. From January to April, the main SSTs of fishing grounds are respectively 1620 C., 1619 C., 1619 C., 1718 C.; the suitable SSTs for high average outputs per haul are respectively 1521 C., 1519 C. and 2021 C., 1520 C., 1720 C., and the corresponding high average outputs per haul are respectively 3451 kg, 3043 kg, 2637 kg, 2630 kg. From July to December, the main SSTs of fishing grounds are respectively 2021 C., 2122 C. and 2326 C., 2527 C., 2122 C., 1921 C., 2021 C. and 2324 C.; the suitable SSTs for high average outputs per haul are respectively 2022 C., 2124 C., 2427 C., 2022 C., 1821 C., 2022 C. and 2324 C., and the high average outputs per haul are respectively 7792 kg, 5463 kg, 2934 kg, 99103 kg, 3652 kg, 3147 kg.

2) Relationship Between Fishery Distribution and Sea Surface Height Anomaly

[0060] The analysis results show that the distribution of cephalopod fisheries is closely related to the sea surface height anomaly, and different months have different suitable SSHA ranges. From January to April, the main SSHAs of fishing grounds are respectively 3525 cm and 55 cm, 4535 cm and 55 cm, 55 cm, 55 cm; the suitable SSHAs for high average outputs per haul are respectively 4020 cm, 5030 cm, 4535 cm, 515 cm, and the corresponding high average outputs per haul are respectively 3747 kg, 4748 kg, 59.22 kg, 2835 kg. From July to December, the main SSHAs of fishing grounds are respectively 3525 cm and 2515 cm, 3525 cm and 55 cm, 3525 cm, 2515 cm, 55 cm; the suitable SSHAs for high average outputs per haul are respectively 4515 cm, 4515 cm, 3515 cm and 55 cm, 3515 cm, 3515 cm and 55 cm, 55 cm, and the corresponding high average outputs per haul are respectively 6780 kg, 4856 kg, 2740 kg, 81104 kg, 4250 kg, 36.96 kg.

3) Relationship Between Fishery Distribution and Sea Depth

[0061] The analysis results show that the distribution of cephalopod fisheries is closely related to the sea depth, and different months have different suitable sea depth ranges. From January to April, the main sea depths of fishing grounds are respectively 4565 m, 5575 m, 5585 m, 6575 m and 8595 m; the suitable sea depths for high average outputs per haul are respectively 5565 m, 4575 m, 5585 m, 8595 m, and the corresponding high average outputs per haul are respectively 44.32 kg, 3043 kg, 2838 kg, 31.96 kg. From July to December, the main sea depths of fishing grounds are respectively 1525 m, 1525 m and 4555 m, 5575 m, 5565 m, 5565 m, 2535 m and 4555 m; the suitable sea depths for high average outputs per haul are respectively 1525 m and 5575 m, 1525 m, 4575 m, 5565 m, 5565 m, 2535 m and 4555 m, and the corresponding high average outputs per haul are respectively 5877 kg, 57.43 kg, 2739 kg, 99.62 kg, 45.12 kg, 3638 kg.

2. Suitability Index (SI)

[0062] According to Table 7, the SST, SSHA and sea depth for maximum SI in January are respectively 1617 C., 55 cm and 5565 m; the SST, SSHA and sea depth for maximum SI in February are respectively 1617 C., 55 cm and 6575 m; the SST, SSHA and sea depth for maximum SI in March are respectively 1819 C., 50 cm and 7585 m; the SST, SSHA and sea depth for maximum SI in July are respectively 2021 C., 3025 cm and 2025 m; and the SST, SSHA and sea depth for maximum SI in September are respectively 2627 C., 55 cm and 5565 m.

TABLE-US-00007 TABLE 7 Suitability indexes based on sea surface temperature, sea surface height anomaly and sea depth in January to March, July and September Month SI value SST/ C. SSHA/cm Sea depth/m January 1.0 16~17 5~5 55~65 0.5 17~20 35~25 45~55 0.1 15~16, 25~5 35~45 20~22 0 <15, <35, <35, >22 >5 >65 February 1.0 16~17 5~5 65~75 0.5 17~19 45~35 55~65 0.1 15~16, 35~25, 45~55 19~21 5~15 0 <15, <45, <45, >21 25~5, >75 >15 March 1.0 18~19 5~0 75~85 0.5 17~18 0~5 55~65 0.1 15~17, 40~35 65~75, 19~20 85~95 0 <15, <40, <55, >20 35~5, >95 >5 July 1.0 20~21 30~25 20~25 0.5 21~22 40~30 15~20 0.1 19~20, 45~40, 60~75 22~24 25~20 0 <19, <45, <15, >24 >20 25~60, >75 September 1.0 26~27 5~5 55~65 0.5 25~26 35~25 65~75 0.1 24~25, 25~15, 45~55 27~28 5~15 0 <24, <35, <45, >28 15~5, >75 >15

3. Comparison of Weight Cases Based on Correlation Factors of Habitat Suitability Index (HSI)

[0063] When the HSI is more than 0.6, it is generally the central fishery. At this time, if the operating haul ratio and the output ratio are larger, the corresponding weight case model is better. It can be seen from Table 8 that Case 1 is optimal, in which the HSI value is more than 0.6, the operating haul ratio and the output ratio are respectively 64.2826 and 67.6196, and the average output per haul is 4451 kg; Case 5 is worst, in which the HSI value is more than 0.6, the operating haul ratio and the output ratio are respectively 57.8826 and 61.92%, and the average output per haul is 4548 kg. Table 8 analyzes the operating haul, the operating output ratio and the average output per haul in January to March, July and September of 2010-2015 based on habitat index models of five cases.

TABLE-US-00008 Case 1 Case 2 Average Average Case 3 Haul Output output per Haul Output output per Haul Output HSI ratio/% ratio/% haul/kg ratio/% ratio/% haul/kg ratio/% ratio/% .sup.0~0.2 4.80 4.90 44.41 2.49 2.87 50.05 2.49 2.87 0.2~0.4 12.54 10.82 37.51 9.44 8.08 37.20 8.75 7.73 0.4~0.6 18.39 16.67 39.41 27.91 24.28 37.81 27.97 23.08 0.6~0.8 32.67 31.20 41.52 34.59 35.16 44.19 26.33 27.72 0.8~1.sup. 31.61 36.41 50.06 25.58 29.61 50.33 34.47 38.59 Case 3 Case 4 Case 5 Average Average Average output per Haul Output output per Haul Output output per HSI haul/kg ratio/% ratio/% haul/kg ratio/% ratio/% haul/kg .sup.0~0.2 50.05 2.49 2.87 50.05 2.49 2.87 50.05 0.2~0.4 38.43 10.87 9.02 36.05 10.19 8.68 37.02 0.4~0.6 35.87 28.76 26.20 39.60 29.45 26.54 39.18 0.6~0.8 45.78 25.35 26.49 45.42 25.35 26.49 45.42 0.8~1.sup. 48.67 32.52 35.42 47.34 32.52 35.42 47.34

[0064] The distribution of Mauritanian cephalopod fisheries and habitat index models thereof under different environmental weights are analyzed according to the production statistical data collected from Mauritanian fisheries in 2010-2015, in combination with sea surface temperature (SST), sea surface height anomaly (SSHA) and sea depth data acquired by satellite remote sensing, thereby providing a basis for forecasting Mauritanian cephalopod fisheries.

[0065] The studies show that the distribution of Mauritanian cephalopod fisheries is closely related to the marine environment, and the suitable environmental ranges of fishing grounds in January to April and July to December are also different to some extent. For the fishing grounds distributed in the waters with SST of 1528 C., SSHA of 4515 cm and sea depth of 1585 m, the optimal SST, SSHA and sea depth are respectively 1622 C., 3525 cm and 55 cm, 1525 m and 4575 m. Among the five Mauritanian cephalopod habitat model cases based on different weights, Case 1 is optimal (weights of SST, SSHA, and sea depth are respectively 0.6, 0.3, and 0.1), and Case 5 is worst (weights of SST, SSHA, and sea depth are all ), that is, the models show that the impacts of different environmental factors on the formation of cephalopod fisheries are different, SST has the greatest impact, followed by SSHA, then the sea depth.

[0066] The impact of environmental factors of different weights on the northwest African waters cephalopod habitat model is discussed according to the production statistical data of a fishery company in combination with satellite remote sensing data, and main environmental factors affecting the distribution of cephalopod habitats and an optimal weight case are obtained to provide a basis for forecasting the central fishery of cephalopods in northwest African waters.

[0067] Although the specific embodiments of the present invention are described above, it should be understood by those skilled in the art that these embodiments are only exemplary, and the scope of the present invention is defined by the appended claims. Many changes or modifications may be made to these embodiments by those skilled in the art without departing from the spirit and scope of the present invention, and these changes and modifications fall within the scope of the present invention.