Research and analysis

Evidence requirement R129: Validating the method of capture of fish

Updated 13 July 2020

1. Requirement overview

1.1 Requirement detail

As part of the MMO’s ongoing work looking at enhancing provenance and traceability in seafood we are keen to investigate new methods of confirming by which method fish sold ashore were originally caught to support and verify other systems for managing compliance and enforcement.

1.2 MMO use

Compliance and Control: An increased level of traceability of catch would increase the range of tools available to the MMO for the management of fish stocks including evaluating current compliance strategies.

1.3 External interest

Inshore fisheries Conservation Authorities

2. Aims and objectives

A pilot project MMO1164 was carried out in 2019, this looked at comparing the metabolomics of mackerel caught with hook and line versus hanging net. The results demonstrated that the biochemical profile of mackerel can distinguish between hanging net and line caught. This differentiation was established using statistical approaches and is hypothesised to result from the different stress levels experienced by fish dependant on capture method.

We are looking to pursue this technology whilst maintaining an interest in any other potential tools to establish the method of capture of sea food.

The following recommendations were made in the pilot project which serves as a guide for how we will further develop the metabolomics technology:

1. Identify the tentatively identified markers in the report, where analytical standards can be purchased, to undertake confirmation analysis of the potential biomarkers of capture stress.

2. A follow-on study to validate this technique in multiple species, including where possible trawl net as well as hanging net and line caught fish, using samples from the same capture method from different locations.

3. A follow-on study with greater sample numbers to validate the approach before it can be used for complementary intelligence/enforcement purposes. To obtain a high statistical power (> 0.8) than the pilot study it is suggested that ≥ 1000 sample replicates per capture type should be analysed and that these samples should be sourced from a range of geographical locations over a time course study.

3. Existing evidence

3.1 Academic

The main approach we are aware of to establish how a fish was caught is metabolomics.

There have been few studies looking comparatively at damage across different gear types such as Veldhuizen et al 2018 which is a synthesis of 85 articles looking at injuries and mortality mostly for trawls and hooks from a welfare perspective.

Weissman et al 2018 showed plasma cortisol values for monkfish with injuries were tenfold higher than plasma cortisol values in minimally stressed reference fish. Plasma cortisol concentrations were significantly higher when air exposure exceeded 20 minutes and tow duration exceeded 70 minutes, suggesting that monkfish may have a maximum threshold at which they can endure capture and handling stresses before they become physiologically compromised.

The MMO1164 pilot study looked for differences in the stress reaction of the fish from the different fishing gears. This was based on the work of Black et al 2017 which demonstrated that it is possible to detect the catch method of fish products using Rapid Evaporative Ionization Mass Spectrometry (REIMS) Metabolic markers of stress for fish have been reported in the literature for both cold stress in Symphysodon aequifasciatus (discus fish) (Wen et al. 2018) and geographical / diet stress in Octopus vulgaris (octopus) (Garrido et al. 2016)

Cook et al. (2018) identify trawl or hanging net capture methods illicit high stress responses as they are the most harmful gear for fish capture.

4. Associated evidence requirements

R131: Validating the origin of capture

5. Further details

For more information or to add further research to the existing evidence list please email evidence@marinemanagement.org.uk

First Created 6 June 2018