| The high sea of Southwest Atlantic Ocean fishing ground is abundant in fisheryresources, which attracts trawl and squid jigging vessels from many countries andregions. Chinese trawl vessels have acceded to fisheries in this area since2008. Atpresent, the research about trawling in this fishing ground was limited in China. Inthis paper, the trawling operating features were summarized based on historical dataand the investigation of fishery resources and environment in this fishing ground.Then, we analyzed the fishing ground environment, the changes of fishery resources,main catches, weights distribution and the biological characteristics of Argentineshortfin squid （Illex argentines）. We further assessed the economic benefit and risk oftrawling in this area. The main results were summarized as follows:Section A: general introduction of trawling characteristics and analyses of theoperating features in high seas of Southwest Atlantic fis hing groundBased on the logbook of voyage2008-2009and2010-2011and field investigationof voyage2010-2011, we presented the general situations of trawling characteristics,classified and summarized the trawling operating features, and contrasted it withsquid jigging fishing. The result showed that: in voyage2008-2009, the operating wasinsufficiency because of the inexperience fishing ground exploitation; whereas itmade quite prepared exploitations of fishing ground in voyage2010-2011. The fishingground has a wide variety of fishery resources. However, the catch composition andcatch yield were slight different in different months and fishing areas due to thecomplexity of fishing conditions. Trawl vessels and squid jigging vessels both fueledoil and transferred catch on the fishing ground to save time and improve workingefficiency. These two kinds of assignment ways had a large overlap in fishing ground,but they would maintain a safe distance in the actual operation. The flow velocity andflow direction in fishing ground were complicated, which led to a more seriouslynegative influence on the squid jigging than that on trawling. Compared with squidjigging, the trawling had a strong capability to resist the risk of substantial changeswith fishery resources. Whereas the trawling was lack of fishing gear selection, had ahigh energy comsumption and can make great damage to the fishery resources. Section B: survey of fishing ground environme nt and analyses on the maincatches by trawl in high seas of Southwest Atlantic Ocean during summer andautumn in2011Fishing grounds environment, fishery resources change, main catches, and weightdistributions were analyzed based on the data of the investigation in high sea ofSouthwest Atlantic Ocean during January-March in2011.The results showed that thebottom of the fishing ground was flat with range in depth from110m to180m, whichwas suitable for trawling. The thermocline and halocline were found in depth of20-80m. Trawl productions increased monthly.11kinds of eonomic species denomiented intrawl productions with accounting for92.26%in weight, including Argentine shortfinsquid （Illex argentinus）, rock cod （Patagonotothen ramsayi）, Argentine hake（Merluccius hubbsi） and Argentine anchovy （Engraulis anchoita）, shakes, etc. Theaverage CPUE was662.0kg/h in trawling survey. The CPUE from January to Marchwere462.8kg/h,713.8kg/h and778.1kg/h, respectively. A slight difference wasfound in the resource density distribution of every month. Catch species compositionand resource density were found significantly different in south and north part offishing ground as there were much more kinds of resources species in the north part offishing ground than that in the south part. The dominant mantle length of Argentineshortfin squid gradually increased from January to March, whereas the dominantmantle length of Argentine hake was shorter in January than that in February andMarch. The dominant mantle length of rock cod was only110-130mm, which wasshorter than their first sexual maturity length. The fishing gear and methods used inthis survey was harmful for the protection of the rock cod resources and should beimproved urgently.Section C: analysis on biological characteristics of Argentine shortfin squidIllex argentinusSpecimen collected from Chinese trawling vessels in the high sea of SouthwestAtlantic from January to April in2010and2011were used to study the biologicalcharacteristics of Argentine shortfin squid.159samples of Argentine shortfin squid was used to measure the morphologicalcharacteristics, gonadal development and weight-length relationship. The resultsindicated that the tentacular arm lengths of the samples are significantly different. Theproportion that the length of left tentacular arm was longer than that of right tenaculararm was equal to the proportion that the length of left tentacular arm was shorter than that of right tenacular. Absolute fecundity was among12-111thousand grains. Theregressions of absolute fecundity （F）, relative mantle length fecundity relative weightfecundity （FW） and mantle length （L）, weight （Wn）, and gonad weight （Wo） indicated:F and FLhad a sigmoid curved correlation with L and Wn; F had a power functioncorrelation with Wo, and the same to FL; FWis in cubic function correlation to L, butin quadratic function correlation to Wn and in sigmoid curve correlation to Wo.Amongthe six models fitting with mantle length, shell length, body weight and net weight,power function model was most suitable for fish weight-length relationship.The trawl samples （n=901） collected in the high sea of Southwest Atlantic Oceanwere studied for the structure of catches, weight-length relationship, stomach fullnessand gonadal development during January-April in2011. The results showed that themantle lengths of the samples tended to increase along with the sampling time. Basedon the data of the stomach fullness, the feeding ability of small mantle length groupswas weaker than that of big mantle length groups, which was also interrelated withfecundity peak period. The regression equations of body weight and mantle lengthwere BW=1.05×10-6ML3.5952for males and BW=4.86×10-6ML3.2810for females.The mantle lengths of first maturity for females and males were191.6mm and182.6mm, respectively. The mean mantle length of maturity stage Ⅴ was less than that ofstage Ⅲ and Ⅳ. The results suggested that the catch composed of South Patagoniapopulation （SPS） and Summer Spawning Stock（SSS） and large individuals from SSSrecruited the populations in finishing ground at the later stages of trawling.Section D: economic benefit and risk analysis of trawl fishe ry in high sea ofSouthwest Atlantic fishing groundMarine fisheries highly depend on environment and the status of fisheries resources.These factors would have an impact on the economic benefits and lead to the risk ofmarine fishing. Studying with the actual production and sales of “Lu Rong Yu6177,6178†pair trawl during2010-2011, we discussed the economic benefits and risks ofthe Southwest Atlantic trawling fisheries. The cost of production was6.53millionRMB per trawl vessel and the catch proceeds from the sales was8.625million RMB.Thus, the profit was2.095million RMB and the profit margin was32.01%.Analysis of its cost structure suggested that the domestic departure increased thecost of inputs, affecting the average operating efficiency of trawling vessels. Thus, theconstruction of fisheries base is imperative. As Argentine shortfin squid and skates had the highest economic values, it is significant to improve the production of thesetwo catches in order to improve production efficiency and increase profits. In thispaper, fisheries risk was analyzed with respect to China’s fisheries policy, fisheriesresources, fisheries environment, and safety management. Reasonable fisheries policycould effectively reduce the production costs and reduce the risk of offshore fishing infisheries industry. It has a great significance to actively develop new gears and lookfor suitable economic species for China’s market to withstand the risks of resourcechanges. Developing new anti-wave fishing vessels and importing advanced trawlersvessels could extend the production time of our fishing vessels in the area, and reduceproduction costs. |
