Synthesis science to the rescue!
How can findings from two robust studies conflict? How do I know if conservation advice to save marine turtles is harming sharks?
By Eric Gilman, Safina Center Scientist in Residence
The news recently reported the tragic death of someone who drank fish tank cleaner in response to US President Trump’s statement that chloroquine cures coronavirus. There are unfortunately numerous examples across disciplines where decisions are based on the latest or most publicized results from a single study, or in this case, on non-expert opinion, in some cases with dire consequences.
Instead, we should rely on evidence from syntheses of accumulated research. This, however, requires that researchers have compiled and synthesized the research that’s already been done. Unfortunately, in my field of fisheries science this is often neglected.
Different research approaches produce findings with different degrees of certainty. At the low end, we have opinions from a single person and qualitative stakeholder surveys, which have a relatively high risk of being biased and wrong. In the middle, findings from single studies provide higher certainty evidence, and for various reasons, such as whether the study was randomized and controlled, individual studies have different degrees of certainty. But there is a risk that the results from that single study is context-specific.
Results may be affected by the specific conditions, such as the study area, study period, species involved and environmental conditions that prevent the results from that single study from being applicable under different conditions. This is why it is common to have conflicting findings from different individual studies.
This is why the validity of a hypothesis cannot be determined from a single study. This brings us to the gold standard of meta-syntheses, such as meta-analyses, which analyze pooled estimates from multiple studies addressing the same question. Due to larger sample sizes plus the number of independent studies, correctly designed meta-analyses can provide estimates with increased precision and accuracy over single studies, with increased statistical power to detect real effects. By synthesizing estimates from a mixture of independent, small and context-specific studies, pooled estimates from meta-analyses are generalizable and hence relevant over diverse settings.
With generous support from The Safina Center Fellowship Program, the Pew Fellows Program in Marine Conservation at The Pew Charitable Trusts and Vulcan Inc., I’m leading three projects that will use the best evidence and account for multi-species conflicts to manage the bycatch (unintended catch) of species of conservation concern in pelagic or blue-water fisheries.
Gilman, conducting a dockside inventory of a longline vessel’s gear, as part of an ecological risk assessment. Photo: Eric Gilman
Longline Bait Meta-Analysis
Our team of 9 researchers from 6 countries is conducting a meta-analysis to assess the effect of different bait types used in open ocean longline fisheries on catch rates of different species. Fisheries that target relatively productive species such as tunas can have large impacts on incidentally caught bycatch species with lower reproduction rates and other ‘slow’ life history traits. As a result, these higher risk species, including seabirds, marine turtles, marine mammals, sharks, rays and some ray-finned fishes, are vulnerable to increased mortality. Different species and sizes of marine predators have different prey, and hence bait, preferences.
This preference is a function of a bait’s chemical, visual, acoustic and textural characteristics and size. Managing bait type offers one tool to reduce the risk of catching at-risk species while maintaining viable catch of target species. Findings from this study will enable fisheries managers to determine how to manage longline bait type to reduce pressure on at-risk bycatch species with acceptable tradeoffs when multi-species conflicts are unavoidable.
Fisheries Ecological Risk Assessment and Bycatch Mitigation Decision Tool
Piecemeal assessment and management of fisheries bycatch is another prevalent problem that our research aims to rectify. Some methods used to mitigate the unwanted catch of species of conservation concern result in multi-species conflicts. For example, a growing number of fisheries management authorities require the use of circle-shaped hooks by drifting longline fisheries to mitigate marine turtle bycatch. While circle hooks reduce leatherback sea turtle catch rates relative to J-shaped hooks of a similar size, they increase the catch of some pelagic sharks (see my recent research on this topic to learn more).
Our research team is conducting ecological risk assessments of tuna fisheries. Determining which populations are of highest ecological risk provides critically important information to guide natural resources management, including when tradeoffs are unavoidable. We’re also developing a decision tree and applying this tool to these tuna fisheries to identify opportunities to increase fishing selectivity to mitigate the bycatch of the most vulnerable populations while accounting for multi-species conflicts.
Metadata Catalogue for Fisheries Synthesis Science
We recently convened, by video conference, the 2020 annual meeting of the Pelagics Topic Group of the ICES-FAO Working Group on Fishing Technology and Fish Behavior. In addition to discussing the longline bait meta-analysis, which was adopted as a research priority by the topic group last year, participants continued to plan for the establishment of a metadata catalogue to support fisheries synthesis science. It’s challenging to explain the benefits of meta-synthesis science. Making the case for metadata catalogues is even more difficult.
Metadata is a set of information describing a dataset of primary research-grade records. A catalogue of metadata is a tool that stores and enables access to this descriptive information on the datasets. Cataloging rich metadata of fisheries-dependent datasets enables: (i) discovery of datasets that are relevant to a specific research question; (ii) determining whether pooling individual datasets is feasible; and (iii) determining how individual datasets can best be integrated.
Over the next year the group will pursue developing and conducting initial testing of the functionalities of a beta version of a metadata catalogue of records for databases assembled for synthesis research, including meta-analyses, and records of other datasets that support priority fisheries synthesis research.
While hopefully very few people are likely to follow baseless and dangerous advice from President Trump, it’s a large challenge to have fisheries management authorities transition from relying on findings from single studies to evidence from more robust meta-syntheses, and to account for multi-species conflicts in their decision-making processes. I’m cautiously optimistic that these three projects will contribute to catalyzing this overdue transition.
And I’m extremely grateful for the enlightened leaders at The Safina Center, The Pew Charitable Trusts and Vulcan Inc. who recognize the value of meta-synthesis science!