The Market Transfer Effect in the Hawaiian Longline Fishery: Why Correlation Does Not Imply Causation

Jason D Scorse,Philip King,Shaun Richards

doi:10.15351/2373-8456.1060

Abstract

A lot of discussion and controversy has surrounded whether the “market transfer” effect in the Hawaii longline swordfish fishery occurred during the swordfish closure of 2001-2004, because of its potential impacts on sea turtle mortality. The primary academic work in support of the market transfer effect during the closure is a paper by Rausser et al. (2009): “Unintended Consequences: The Spillover Effects of Common Property Regulations.” In this paper, the authors claim to find evidence in support of the market transfer hypothesis.To our knowledge, no analysis has yet been undertaken to assess whether this analysis is sound, and yet it remains the principle academic work in support of the market transfer effect. It is cited frequently in hearings and briefings in which the case is made to reduce fishing restrictions on US fleets. Our analysis shows that Rausser et al. is flawed; the authors erroneously linked the increased catch by foreign fleets in the EPO to the Hawaii closure, when in fact there is no evidence of a causal relationship.

Highlights

A significant amount of discussion has surrounded the question as to whether the market transfer effect in the Hawaii longline swordfish fishery occurred during the US swordfish closure of 2001-2004, primarily due to the potential impact on sea turtle mortality
Our analysis indicates that Rausser et al.’s and Chan and Pan’s conclusions about increased global turtle mortality are not robust, because while they provide evidence that demonstrates a correlation between the US closure and a market transfer effect, this correlation can be explained by other factors
For the market transfer hypothesis to be robust, one must demonstrate that foreign fleets in the EPO increased their catch in response to the closure

Summary

INTRODUCTION

A significant amount of discussion has surrounded the question as to whether the market transfer effect in the Hawaii longline swordfish fishery occurred during the US swordfish closure of 2001-2004, primarily due to the potential impact on sea turtle mortality. Other studies have examined the market transfer effect in the Hawaii swordfish fishery (see Sarmiento, 2006, Bartram et al, 2010, Mukherjee, 2015, Squires et al, 2016), but all of them essentially accept the results from Rausser et al and Chan and Pan. Our analysis indicates that Rausser et al.’s and Chan and Pan’s conclusions about increased global turtle mortality are not robust, because while they provide evidence that demonstrates a correlation between the US closure and a market transfer effect, this correlation can be explained by other factors. The Philippines only fish for swordfish using municipal vessels and primarily use single hook hand lines, which would not overlap with the part of the WCPO used by the Hawaii longline fishery nor very likely result in a large increase in turtle mortality Based on these findings, we conclude that there is insufficient evidence to suggest that the market transfer effect occurred in the Hawaii swordfish fishery during the closure of 2001-2004, and insufficient evidence to suggest more turtles were killed. There are many factors that influence catch which need to be examined, which is especially true for swordfish

WHY THE SPANISH CATCH DRAMATICALLY INCREASED POST-2001

EPO CATCH BY COUNTRY FROM 2000-2013

ADDITIONAL EVIDENCE

THE CHAN AND PAN STUDY

Findings

SUMMARY AND CONCLUSION