Bias in self‐reported parasite data from the salmon farming industry

Abstract

Many industries are required to monitor themselves in meeting regulatory policies intended to protect the environment. Self-reporting of environmental performance can place the cost of monitoring on companies rather than taxpayers, but there are obvious risks of bias, often addressed through external audits or inspections. Surprisingly, there have been relatively few empirical analyses of bias in industry self-reported data. Here, we test for bias in reporting of environmental compliance data using a unique data set from Canadian salmon farms, where companies monitor the number of parasitic sea lice on fish in open sea pens, in order to minimize impacts on wild fish in surrounding waters. We fit a hierarchical populationdynamics model to these sea-louse count data using a Bayesian approach. We found that the industry's monthly counts of two sea-louse species, Caligus clemensi and Lepeophtheirus salmonis, increased by a factor of 1.95 (95% credible interval: 1.57, 2.42) and 1.18 (1.06, 1.31), respectively, in months when counts were audited by the federal fisheries department. Consequently, industry sea-louse counts are less likely to trigger costly but mandated delousing treatments intended to avoid sea-louse epidemics in wild juvenile salmon. These results highlight the potential for combining external audits of industry self-reported data with analyses of their reporting to maintain compliance with regulations, achieve intended conservation goals, and build public confidence in the process.

Next-generation matrices for marine metapopulations: the case of sea lice on salmon farms*

“…However, there is abundant evidence that in the Broughton Archipelago sea lice populations on many salmon farms will grow exponentially in the absence of treatment by farm managers [64,65,66,52,67]. This discrepancy may be due to the fact that while the hydrodynamic and particle tracking models give good estimates of sea louse dispersal between farms [52], they likely underestimate the number of sea louse larvae that remain inside a salmon farm.…”

Salmon lice in the Pacific Ocean show evidence of evolved resistance to parasiticide treatment

“…Salmon-louse counts were performed by farm staff as described by Godwin et al 27 . In short, salmon-louse counts were usually performed at least one per month by capturing 20 stocked fish in each of three net pens using a box seine net, then placing the fish in an anesthetic bath of tricaine methanesulfonate (TMS, or MS-222) and assessing the fish for motile (i.e., pre-adult and adult) L. salmonis by eye.…”

Sea lice (Lepeophtherius salmonis) detection and quantification around aquaculture installations using environmental DNA

“…However, disease, welfare and environmental issues are major each pen, the numbers may not be representative for the total abundance level of L. salmonis in the surrounding environment. It has also recently been shown that Canadian salmon farming companies are regularly under-reporting the number of lice on their fish, most likely to avoid expensive delousing treatments [23]. Clearly, there is a need for a more cost-efficient, accurate, and less intrusive method for monitoring this species at any life stages to identify farm localities with high salmon lice density, and thereby high infestation pressure, at an early stage.…”