Report

Tracking the global footprint of fisheries

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Science  23 Feb 2018:
Vol. 359, Issue 6378, pp. 904-908
DOI: 10.1126/science.aao5646

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  • RE: Let the prohibited fishing zone be worthy of its name
    • Cheng Chen, Research Associate, East China Sea Fisheries Research Institute, Chinese Academy of Fishery Science, Shanghai, 200090, P. R. China
    • Other Contributors:
      • Zunlei Liu, Research Associate, East China Sea Fisheries Research Institute, Chinese Academy of Fishery Science, Shanghai, 200090, P. R. China
      • Jianzhong Ling, Senior Research Fellow, East China Sea Fisheries Research Institute, Chinese Academy of Fishery Science, Shanghai, 200090, P. R. China
      • Yong Liu, Senior Research Fellow, East China Sea Fisheries Research Institute, Chinese Academy of Fishery Science, Shanghai, 200090, P. R. China
      • Liping Yan, Senior Research Fellow, East China Sea Fisheries Research Institute, Chinese Academy of Fishery Science, Shanghai, 200090, P. R. China

    In their report (23 Feb 2018, p.904), Kroodsma et al. identify vessel characteristics and analyse signal positions, training samples, build model, then indicate annual intensity of fishing effort (Hours of fishing km-2 yr-1) based on vessel movement patterns(2012-2016)as determined with the Automatic Identification System (1-2). We argue that the statistical capture productions (in weight) on both sides of the prohibited fishing line in China’s coastal waters seem not to match with this fishing effort (Fig.1). Because all commercial trawler fishings are forbidden in the west of the line (i.e. " the prohibited fishing zone", Fig.1) by the Fisheries Law of China (3). As we calculate a ratio of the production by trawler fishing to the total domestic marine catches of China from 2012 to 2016 is 47.71%, 47.96%, 47.77%, 47.22% and 46.88%, respectively, according to the China Fisheries Yearbook (4). We know that not all other type of fishing (except trawler fishing) make production only within the zone and there is also a small production by trawl inside the zone illegally. Actual yields on both sides are very difficult to count due to disaggregated catch data (1). Thus, we consider that capture yields on both sides are nearly equate. However, Kroodsma's map suggest entirely different fishing effort on both sides (Fig.1).

    Why does the apparently much higher fishing effort inside the zone produce nearly same yield compared with that of the outside? One possi...

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    Competing Interests: None declared.
  • False Equivalence in Footprints
    • Elizabeth Havice, Associate Professor, Department of Geography, University of North Carolina-Chapel Hill
    • Other Contributors:
      • Martin D. Smith, George W. Woodwell Distinguished Professor of Environmental Economics, Nicholas School of the Environment and Department of Economics, Duke University

    Kroodsma et al. develop and analyze novel data on global fishing effort with implications for ocean governance and food systems (1). However, their false equivalence between terrestrial and marine footprints diverts attention from the paper’s significant findings. They write that fishing “has a spatial extent more than four times that of agriculture” and “provide[s] only 1.2% of global caloric production for human consumption,…” (1).

    The environmental impacts of terrestrial and marine food production are different (2). The authors count space toward footprint if fishing took place within a grid cell of 0.5⁰. Converting a 0.5⁰ square of tropical rainforest to soybean monoculture is not comparable to a time series of fishing sets in that same amount of area in the ocean. How many sets must be recorded in a cell, and over what time frame, for equivalence with even the average intensity of terrestrial agriculture?

    In the environmental sciences, “footprint” is a metaphor for impact, not simply a measure of spatial extent (3). Comparative dietary studies find that restricting animal protein to seafood reduces environmental impacts compared to diets that include ruminants (2, 4). Suggesting a false equivalence could encourage environmentally minded consumers to reject marine animal protein for less sustainable terrestrial animal protein.

    Differing spatial structures also undermine a comparison of marine and terrestrial food production footprints. Fishing tak...

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    Competing Interests: None declared.
  • RE: The wonderful work needs to be further verified
    • Cheng Chen, Research Associate, East China Sea Fisheries Research Institute, Chinese Academy of Fishery Science, Shanghai, 200090, P. R. China
    • Other Contributors:
      • Zunlei Liu, Research Associate, East China Sea Fisheries Research Institute, Chinese Academy of Fishery Science, Shanghai, 200090, P. R. China
      • Jiahua Cheng, Senior Research Fellow, East China Sea Fisheries Research Institute, Chinese Academy of Fishery Science, Shanghai, 200090, P. R. China

    In the report Kroodsma et al. identify vessel characteristics and analyse signal positions, training samples, build model, then indicate intensity of fishing effort based on vessel movement patterns as determined with the Automatic Identification System (AIS). Therefor they improve the accuracy of map of the global footprint of fisheries (1-2). They pay more focus on China and conclude that modern fishing is likely shaped by policy. Just for this reason, yet they ignore the fact evidently that all commercial motorized trawler fishings are forbidden strictly in the west of the prohibited fishing line along China’s coast, which is nearly along 40 m isobath, by the Fisheries Law of China (3).

    For example, from 2014 to 2016 the total capture landing in the Zhoushan fishing ground, as the largest fishing ground in China, are 3.24, 3.37 and 3.47 million tons, respectively. Among them the production by trawler fishing in the east of the line are 1.93 (59.6%), 2.04 (60.5%), and 2.10 (60.5%) million tons, respectively (4). Previous study also suggests that the trawler fishery (in the east of the line) accounts for 52.2% of the total domestic marine capture landing of China in 2013 (5). Thus the actual fishing efforts on both sides of the prohibited fishing line in China’s coastal ocean are not consistent with the indicating by the map of footprint of fisheries.

    We argue that such map could mislead reader and overstate the actualy fishing activity, especially within...

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    Competing Interests: None declared.
  • RE: A FEW REMARKS

    When you compare fishery with agriculture you are pairing a hunting with a croping. That's not, in my opinion, an accurate way to analize. On the other hand, modern agriculture is not that static. I mean, nowadays many agricultural entrepeneurs move around the world looking for conditions to their crops.

    Competing Interests: None declared.