分类:捕鱼策略

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Conover, D. O. (2002). Sustaining Fisheries Yields Over Evolutionary Time Scales. Science, 297(5578), 94-96. https://doi.org/10.1126/science.1074085

Abstract

Fishery management plans ignore the potential for evolutionary change in harvestable biomass. We subjected populations of an exploited fish (Menidia menidia) to large, small, or random size-selective harvest of adults over four generations. Harvested biomass evolved rapidly in directions counter to the size-dependent force of fishing mortality. Large-harvested populations initially produced the highest catch but quickly evolved a lower yield than controls. Small-harvested populations did the reverse. These shifts were caused by selection of genotypes with slower or faster rates of growth. Management tools that preserve natural genetic variation are necessary for long-term sustainable yield.

总结和评论

这篇文章[1]的作者养了好几年的鱼,每过一段时间就去捕捉这些鱼,让剩下的鱼继续长大,然后继续捕捉。通过这个实验,作者想回答“到底捉大放小,捉小放大,还是随机捕捉”会使得最后的长期鱼获更好的问题。作者的研究发现,对于一开始没有区别的鱼龄一致的鱼群,捉大放小会使得长期鱼获个体变小,捉小放大反而更好。这样作者就提出了对现在的通常的捕鱼策略的挑战,更进一步注意到了鱼的性状(以及背后的基因,在这里主要是成长速度和背后的基因)和捕鱼策略之间的关系,提出来了一个什么是更好的捕鱼策略的问题。

当然,整个研究是单一鱼群的,对于实际的渔业作业,忽略种群相互作用是一个非常大的近似。同时,由于其实验中捕获力度非常大(90%都要捕杀掉)留下来的基本上都是同一代的鱼,代际动力学,也就是捉大放小的背后的考虑(让那些还没有成年的鱼得到长大并且繁衍下一代的机会),就基本不起作用了。因此,如果要得到真的能够指导捕鱼的策略,则还需要进一步研究。当然,这个工作已经有大量的后续研究[2][3][4][5][6][7][8][9][10][11],甚至有人讨论了只捕捉某个区间大小的鱼的策略,以及包含种间动力学的策略。

下一步工作

考虑具有两种不同成长速度的鱼,在不同的捕鱼策略下的进化。由于只要捕得太狠则所有的策略下都会出现鱼获整体变小变少,因此要考虑捕鱼周期和生长周期的匹配问题。例如,两种捕鱼方式都能够保证鱼群长期繁衍的基础上来讨论不同策略的结果。

同时,要有让鱼龄出现不一致的条件。如果鱼龄基本一致,则捕鱼确实就是“人工(反向)选择”的作用:都给了每一个与充分成长的机会了,这时候,留下来的小鱼肯定就是生长速度(由相应的基因决定)本来就是慢的鱼。这样长期下去,肯定是把生长的快的淘汰了,而留下来了生长的慢的基因。那么,如何让鱼龄不一致呢?捕的比例可能得小一点,而且是每条鱼按照一定的比例(大小的函数)来捕杀,而不是之前的大于多少的都确定捕杀。同时,得养很多很多代,这样就能够拉开同时期的鱼的代际差别。

更复杂的每一代的鱼的生长速度和繁殖能力的区别是否要包含在这个模型里面,也需要考虑。

多种鱼之间的相互作用的影响,也是一个需要将来讨论的问题。

写下来包含以上因素的微分方程,看一看多代演化的结果。

参考文献

  1. Conover, D. O. (2002). Sustaining Fisheries Yields Over Evolutionary Time Scales. Science, 297(5578), 94–96. https://doi.org/10.1126/science.1074085
  2. Aramayo, V. (2015). Lower selectivity can help heavily exploited fish populations. Fisheries Research, 172, 261–264. https://doi.org/10.1016/j.fishres.2015.07.028
  3. Breen, M., Graham, N., Pol, M., He, P., Reid, D., & Suuronen, P. (2016). Selective fishing and balanced harvesting. Fisheries Research, 184, 2-8. https://doi.org/10.1016/j.fishres.2016.03.014
  4. Bunwong, K., & Sae-jie, W. (2017). Evolutionary consequences of age-specific harvesting: age at first reproduction. Advances in Difference Equations, 2017(1), 157. https://doi.org/10.1186/s13662-017-1214-2
  5. Froese, R., Walters, C., Pauly, D., Winker, H., Weyl, O. L. F., Demirel, N., … Holt, S. J. (2016). A critique of the balanced harvesting approach to fishing. ICES Journal of Marine Science: Journal Du Conseil, 73(6), 1640–1650. https://doi.org/10.1093/icesjms/fsv122
  6. Gwinn, D. C., Allen, M. S., Johnston, F. D., Brown, P., Todd, C. R., & Arlinghaus, R. (2015). Rethinking length-based fisheries regulations: the value of protecting old and large fish with harvest slots. Fish and Fisheries, 16(2), 259–281. https://doi.org/10.1111/faf.12053
  7. Jana, D., Agrawal, R., Upadhyay, R. K., & Samanta, G. P. (2016). Ecological dynamics of age selective harvesting of fish population: Maximum sustainable yield and its control strategy. Chaos, Solitons & Fractals, 93, 111–122. https://doi.org/10.1016/j.chaos.2016.09.021
  8. Kolding, J., Law, R., Plank, M., & van Zwieten, P. A. M. (2015). The optimal fishing pattern. 收入 J. F. Craig (编), Freshwater Fisheries Ecology (页 524–540). https://doi.org/10.1002/9781118394380.ch41
  9. Law, R., & Plank, M. J. (2018). Balanced harvesting could reduce fisheries-induced evolution. Fish and Fisheries, 19(6), 1078–1091. https://doi.org/10.1111/faf.12313
  10. Morbey, Y. E., & Mema, M. (2018). Size-selective fishing and the potential for fisheries-induced evolution in lake whitefish. Evolutionary Applications, 11(8), 1412–1424. https://doi.org/10.1111/eva.12635
  11. Uusi-Heikkilä, S., Whiteley, A. R., Kuparinen, A., Matsumura, S., Venturelli, P. A., Wolter, C., … Arlinghaus, R. (2015). The evolutionary legacy of size-selective harvesting extends from genes to populations. Evolutionary Applications, 8(6), 597-620. https://doi.org/10.1111/eva.12268

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