An assessment of observer deployment on industrial trawlers in Ghana

Abstract

The most reliable way of monitoring fisheries performance is by a standardized reporting of relevant data by well-trained observers. The Fisheries Enforcement Unit (FEU) of Ghana has trained about 200 observers for deployment on Ghanaian flagged trawlers to curb illegalities committed during fishing expeditions and also to collect data that cannot be taken when using the Vessel Monitoring System (VMS). These observers were deployed on 831 trips of industrial trawl vessels for fishing expeditions from July 2015 to March 2019. Total (100%) on-board observer coverage, however, started from March 2018 since January and February were declared as closed season. Using the catch data from March to December 2018, a sub-sample of 162 observer trips out of the 543 observer trips in 2018 was compared to catch data declared and landed by the trawler operators. Observers declared a total of 19,771.08 tonnes of fish against total tonnage of 16,468.21 declared by trawler operators indicating a difference of 3,302.87 tonnes between them. This difference in tonnage is significant and it represents 20% increment in the data presented by the observers. There is also 75.6% correlation between the two data sources and this shows a strong linear relationship. Forty-six (46%) of the total catch recorded was by-catch and this figure is quite alarming. The trawler operators obeyed the minimum fishing gear mesh size regulation of 60 mm and fishing depth beyond 30 meters. The total observer coverage has helped to overcome observer effect and also reduced bias in data collection. Data submitted by these observers provide useful complimentary information on the state of a fish stock.