Since it was first published in 1998 (Pauly et al., 1998), the ‘fishing down’ concept has been accepted and adopted by a broad community of marine and freshwater scientists. However, there have also been objections, notably by staff of the Food and Agriculture Organization of the United Nations (FAO) and fisheries scientists at the University of Washington, Seattle.
These objections are based mainly on imputations and misunderstandings, and this section of the ‘fishing down’ web site is dedicated to pointing out, and thus overcoming the misunderstandings behind much of the controversy. An example of this, which we think contributes to clearing up these issues is that by D. Pauly in Science Chronicles, reproduced below. See also Stergiou and Tsikliras (2011) below for an illuminating discussion. To access the large number of regional, national and sub-national studies illustrating the occurrence of ‘fishing down’, see Case Studies.
Focusing One’s Microscope
By Daniel Pauly
“Scientific discoveries are often a matter of focusing one’s microscope - actual or virtual - and so rules have emerged on how to focus…………
“In 1998, my co-authors and I first described the phenomenon now known as ”fishing down marine food webs” mainly because we were lucky both with the data available at the time and with the setting of our conceptual “microscopes.” ……….
“Subsequent research by myself and my associates and by a number of independent authors throughout the world has helped to address the arguments of early critics of the fishing-down concept and to establish its general occurrence […] and intensity (about 0.05 - 0.10 TL per decade). Also, we were able to identify many of the factors that can cause the effect to be masked, thus knocking our microscope out of focus……..
“In late 2011, Nature published a paper on trends in fisheries that also had its microscope out of focus, and which consequently presented a confused picture, with fishing down sometimes visible, sometimes not..........
Fishing down, fishing through and fishing up: fundamental process versus technical details
By Konstantinos Stergiou and Athanassios Tsikliras
“Fishing through, fishing up […] and the question of agreement between MTL from catches and surveys have been used to question fishing down the marine food web as well as the use of the marine trophic index as an effective ecosystem indicator…………
”We believe that fishing down, fishing through and fishing up the food web are not incompatible but only appear so because of confusion. Fishing down is an ecological process, which can be expected to either occur or not, i.e. it is a hypothesis which can be falsified and replaced by an alternative hypothesis that must also rely on ecological principles (rather than technicalities). In contrast, fishing through and fishing up reflect technical issues related to biases in the available data and/or to fishing behaviour and thus do not falsify fishing down………..
“Thus, MTL remains one of the most operational indices available for testing fishing down. It is without doubt that, in various cases, MTL will not be effective because of various technical confounding factors, which can be clarified by local experts. Undoubtedly, MTL can be misused, usually when confounding effects cannot be properly disentangled, and thus it must be used and interpreted with caution.”