Comments on "Analysis of permanent magnets as elasmobranch bycatch reduction devices in hook-and-line and longline trials"

TL;DR

The paper critiques a 2011 study on using magnets to reduce elasmobranch bycatch, highlighting data inconsistencies and inadequate experimental design, and emphasizes the need for more rigorous testing with larger samples.

Contribution

It provides a critical review of previous research, pointing out methodological flaws and the necessity for improved experimental approaches in studying magnetic hooks.

Findings

Inconsistencies in data supporting the first hypothesis.

Insufficient data and poor design for testing the second hypothesis.

Grouping all teleosts in analysis is scientifically unjustified.

Abstract

A recent study (Fish. Bull. 109:394-401 (2011)) purportedly tests two hypotheses: 1. that the capture of elasmobranchs would be reduced with hooks containing magnets in comparison with control hooks in hook-and-line and longline studies. 2. that the presence of permanent magnets on hooks would not alter teleost capture because teleosts lack the ampullary organ. Review of this paper shows some inconsistencies in the data supporting the first hypothesis and insufficient data and poor experimental design to adequately test the second hypothesis. Further, since several orders of teleosts are known to possess ampullary organs and demonstrate electroreception, grouping all teleosts in a study design or data analysis of magnetic hook catch rates is not warranted. Adequate tests of the hypothesis that permanent magnets or magnetized hooks do not alter teleost capture requires a more careful study design and much larger sample sizes than O'Connell et al. (Fish. Bull. 109:394-401 (2011)).