Efficiency of Industrially Processed Longline Baits - An Ethological Approach

Abstract

Industrially processed bait for longline fishing is currently being developed as an alternative to the less sustainable natural bait sources, such as squid and herring. The net catch efficiency of processed baits will depend on the behavior of target fish in phases of interaction, guided by sensory evaluation. In the following, I will evaluate the effectiveness of an ethological approach in determining the relative importance of each of these different behavioral phases for bait efficiency. Herein, direct, and continuous video observations of fish behavior towards baited hooks in the natural environment will be employed. Industrially processed baits (Ecobait variants) will be employed as a model, to be compared to commonly used natural baits. Fish behavior towards these bait categories was categorized and compared, and analyzed to determine to what extent this method can guide further development and improvement of more efficient processed baits. As an additional subgoal, I include metadata on environmental factors (tide, time of day, lunar phase, habitat type, species) for each test occasion, to determine whether there is resolution to also investigate the effect of such factors on behavior towards natural vs processed baits. Natural baits were found to induce a significantly higher frequency of interactions than industrially processed baits, at phases of the interaction cycle corresponding to the fish deeming the bait appetizing and attacking it. Also, regarding behavior towards baited hooks, the degree of contrast between natural and processed baits were found to be affected by both environmental factors and species. For example, fish appeared to be both more active and selective during high and rising tide than during ebb periods. No significant differences were found in the frequency of interactions for early stage, exploratory behaviors. In conclusion, the method utilized in this experiment to gather data was found to yield measurable differences in interaction rates on different bait types allowing for more precise and less resource intensive testing than traditional test fishing.

Industrially processed bait for longline fishing is currently being developed as an alternative to the less sustainable natural bait sources, such as squid and herring. The net catch efficiency of processed baits will depend on the behavior of target fish in phases of interaction, guided by sensory evaluation. In the following, I will evaluate the effectiveness of an ethological approach in determining the relative importance of each of these different behavioral phases for bait efficiency. Herein, direct, and continuous video observations of fish behavior towards baited hooks in the natural environment will be employed. Industrially processed baits (Ecobait variants) will be employed as a model, to be compared to commonly used natural baits. Fish behavior towards these bait categories was categorized and compared, and analyzed to determine to what extent this method can guide further development and improvement of more efficient processed baits. As an additional subgoal, I include metadata on environmental factors (tide, time of day, lunar phase, habitat type, species) for each test occasion, to determine whether there is resolution to also investigate the effect of such factors on behavior towards natural vs processed baits. Natural baits were found to induce a significantly higher frequency of interactions than industrially processed baits, at phases of the interaction cycle corresponding to the fish deeming the bait appetizing and attacking it. Also, regarding behavior towards baited hooks, the degree of contrast between natural and processed baits were found to be affected by both environmental factors and species. For example, fish appeared to be both more active and selective during high and rising tide than during ebb periods. No significant differences were found in the frequency of interactions for early stage, exploratory behaviors. In conclusion, the method utilized in this experiment to gather data was found to yield measurable differences in interaction rates on different bait types allowing for more precise and less resource intensive testing than traditional test fishing.