基于理想自由分布理论对CPUE与渔业资源关系的探讨——以我国近海鲐灯光围网渔业为例

为提高水下集鱼灯光场分布计算精度，本实验采用集鱼灯光谱数据、光度分布数据和海水固有光学参数，基于蒙特卡罗模拟方法构建了新的光场传输数值模拟方法，将光束能量离散成大量光子，通过追踪光子路径计算水下集鱼灯形成的光场强度，并开展水槽实验对计算方法进行了验证。同时，提出了新的集鱼灯光场分布评价指标${I_{{rm{ds}}}}$和${A_{{rm{ds}}}}$。利用模型分析了海水的叶绿素a质量浓度、散射作用类型和散射相位函数HG (Henyey Greenstein)中非对称参量$g$的取值对水下光场分布的影响。结果显示，①叶绿素a质量浓度从1 mg/m³增加到5 mg/m³，LED集鱼灯${A_{5{rm{m}}}}$ 减少了72.73%，MH集鱼灯${A_{5{rm{m}}}}$减少了72.17%；LED集鱼灯${I_{5{rm{m}}}}$减少了66.69%，MH集鱼灯${I_{5{rm{m}}}}$减少了53.29%。②当海水介质引起的散射类型分别为米氏散射和瑞利散射时，MH集鱼灯${I_{5{rm{m}}}}$分别为1058.48和1020.5 lx， LED集鱼灯${I_{5{rm{m}}}}$分别为1057.96和992.42 lx。③非对称参量$g$从0.80增加到0.99，MH集鱼灯的${A_{5{rm{m}}}}$增加了22.05%；LED集鱼灯的${A_{5{rm{m}}}}$增加了23.10%；MH集鱼灯形成的${I_{5{rm{m}}}}$增加了16.61%；LED集鱼灯形成的${I_{5{rm{m}}}}$增加了14.52%。研究表明，近海水体中叶绿素a质量浓度、HG散射函数中非对称参量对集鱼灯光场分布有显著影响，散射类型对集鱼灯光场分布无显著影响。本研究提出的数值模拟方法可准确计算近海水体中集鱼灯光场分布，为渔业监管和集鱼灯合理应用提供科学依据。

The relationship between CPUE and fish abundance based on ideal free distribution theory: take the large light purse seine fishery of mackerel in Yellow Sea and East China Sea as an example

The illumination distribution in water is an important subject for efficient application research of fishing lamp. The traditional numerical calculation method could not accurately calculate the illumination distribution of the underwater fish gathering lamp in the offshore water. A new computing model of underwater illumination of fishing lamp was developed based on Monte Carlo method by using spectrum and luminous intensity of lamps and the inherent optical properties of seawater. Firstly, the vertical marine section was set as the target surface and divided it to some grids; secondly, photons with specific wavelength and direction were generated by random number method, and then the attenuation coefficient of each photon was calculated by using chlorophyll concentration data, optical characteristics of pure seawater and its relationship with absorption and scattering coefficients; finally, all photons were emitted, and their transmission paths were tracked. The photons were recorded only if they fell into the target surface and the illuminance value of each grid was calculated according to the recorded position of photons. The calculation method was verified with flume test through collecting water samples. The ${A_{{rm{ds}}}}$—area of closed region which enclosed by 0.1 lx contour line in marine section which $ds$ m away from underwater fishing lamp and the ${I_{{rm{ds}}}}$—maximum illuminance value in marine section were used to characterize the spatial distribution of light field in water. In this paper, the effect of chlorophyll concentrations, scattering type in the marine water and the scattering asymmetry parameters on the illumination distribution of LED fishing lamp and MH fishing lamp were analyzed through numerical simulation. The results showed: (1) with the chlorophyll concentration increases from 1 mg/m³ to 5 mg/m³, the ${A_{5{rm{m}}}}$ of LED lamp decreased from 1073.90 m² to 292.87 m², which means ${A_{5{rm{m}}}}$ has reduced by 72.73%; the ${A_{5{rm{m}}}}$ of MH lamp decreased from 1094.51 m² to 304.57 m², which means ${A_{5{rm{m}}}}$ has reduced by 72.17%; the ${I_{5{rm{m}}}}$ of MH decreased from 972.76 lx to 454.42 lx, which means the ${I_{5{rm{m}}}}$ has reduced by 53.29%; the ${I_{5{rm{m}}}}$ of LED decreased from 956.48 lx to 318.60 lx, which means the ${I_{5{rm{m}}}}$has reduced by 66.69%.(2) when scattering type of the ocean water is Mie scattering and Rayleigh scattering, the ${I_{5{rm{m}}}}$of MH is 956.48 lx and 318.60 lx, respectively; the ${I_{5{rm{m}}}}$of LED is 1057.96 lx and 992.42 lx, respectively.(3) with the scattering asymmetry parameters increases from 0.80 to 0.99, the ${A_{5{rm{m}}}}$ of MH lamp decreased from 1094.89 m² to 1336.40 m², ${A_{5{rm{m}}}}$ increased 22.05%; the ${A_{5{rm{m}}}}$ of LED lamp decreased from 1076.52 m² to 1325.21 m², ${A_{5{rm{m}}}}$ increased 23.10%; the ${I_{5{rm{m}}}}$ of MH increased from 962.52 lx to 1122.48 lx, ${I_{5{rm{m}}}}$increased 16.62%; the ${I_{5{rm{m}}}}$ of LED increased from 980.74 lx to 1123.22 lx, ${I_{5{rm{m}}}}$increased 14.53%. It was found chlorophyll concentrations had a significant effect on illumination distribution of fishing lamp, while the scattering type and the scattering asymmetry parameters on the illumination distribution had no significant effects. The numerical simulation method proposed in this paper can accurately calculate the illumination distribution of fishing lamps in offshore waters, which would provide scientific basis for fishery supervision and reasonable application of fishing lamps.