Some marine animals die or may be severely injured by some fishing gear. This accidental capture is often due to the fact that some species are attracted to the food offered and are caught at the time of attempting to access it; is the case of longline fishing, but also some nets or traps. In other cases, the capture can occur when the animal accidentally approaches the art, as is often the case with some nets.

This accidental capture in fishing gear is a great threat to many of the great marine animals (megafauna marina), along with ocean pollution, overfishing, loss of coastal habitat for urban development and the introduction of predators in the areas of reproduction of some species.

In addition, for many fishermen, the frequency of these episodes is also a hindrance, as they cause discomfort, slow down work, damage art and lose fishing opportunities.

Due to the extent of the geographical area, the difficulty and cost of obtaining data in a medium such as the sea, and the heterogeneity and irregularity of accidental capture events, both in space and time, we do not currently have enough quality data to assess some of the factors that may be affecting these accidental catches or the effects thereof on the populations of the affected species.

Project Bycatch

The Bycatch project aims, on the one hand, to improve communication and collaboration between scientists and fishermen, and on the other hand, to increase our knowledge and quantification of the effects of accidental catches on the marine megafauna, that is, on cetaceans, seabirds, marine turtles and sharks and rays.

Through this project we intend to involve the fishing sector, both professional and recreational fishermen, to improve our knowledge of the problem and look for solutions for a reduction in accidental catches. The information that this sector can provide is very valuable, both to help the protection of the marine megafauna to reduce the inconvenience and costs of the fishermen involved in these events.

What are data collected for?

Many of these species captured into fishing gear are threatened and we must know their main threats to reduce or mitigate the effects and improve the viability of their populations.

The short and long-term monitoring of many of these species provides us with some information to disentangle, through mathematical models, some of the main factors that regulate the populations in these species and consequently advise on the best measures to take to ensure their conservation.

We know that some of these species suffer from accidental catches in fishing gear because we have records and the same fishermen communicate these events. But in order to develop demographic models and quantify the effects of these catches on different species, we need more data about these events and the animals that are captured.

Especially valuable to carry out some of our models, are the observations at sea of previously marked animals.

Ringing of Audouin’s chicks on the Punta de la Banya in the Ebro Delta. Photo Meritxell Genovart.

Ringed Audouin’s gull fishing. Photo Pep Arcos.

Ringing of chicks and adults of Scopoli’s shearwaters in Mallorca. Photos M. Fowler and J.M. Igual.

Capture and ringing of an European or common shag in the Costa Brava, Catalonia. Photo Júlia Ferrer.

Capturing, marking and breeding monitoring of a Leatherback turttle in Costa Rica by “The Lethearback Trust”. Photo: Bibi Santidrian.

Aduouin’s gull with fishing hooks inside. Photo Torreferrussa.

Shearwaters accidentally caught in fishing gear on the Catalan coast. Photo Pep Arcos.

The development of an application for mobile devices, easy to use and that guarantees the anonymity of fishermen, should allow us to collect many more quality data and open a secured communication channel between fishermen, both professionals and recreational, and the scientific community involved.

Thanks to the information provided by fishermen, scientists will rigorously estimate the annual mortality rate of certain marine species of conservation interest such as seabirds, cetaceans, sea turtles or sharks and rays at different types of fishing (longline and fishing nets), and assess the impact of these mortalities at the population level. The involvement of fishermen will also help to determine the best measures to reduce these catches, taking into account all the sectors involved.