Line of action:

Status:

Execution date:

General Objective:

To evaluate the possibility of reducing the discards landed by bottom trawling in the Gulf of Cadiz and in the Cantabrian-Northwest Fishing Ground.

Specific objectives:

1. To characterise the survival and/or mortality rates of the main commercialised species caught in the Gulf of Cadiz and the Cantabrian-Northwest fishing ground by bottom trawling.
2. Assess the resilience of species that survive trawling.
3. To publicize the results as a possible solution for the reduction of discards.

The SUREDEPAR project has made it possible to characterize the survival rates and resilience of demersal species that survive trawling. To this end, the ARSA 0318 and 1118 oceanographic campaigns have been carried out in the Gulf of Cadiz, carrying out three survival and recovery experiments for Norway lobsters, octopuses and catsharks.

Norway lobsters have presented significant differences in survival rates according to the season, being higher in spring compared to autumn (68.4 ± 7.1 % and 33.8 ± 7.8 %, respectively). These differences in survival rates may be due to the high temperatures recorded in the water during the autumn campaign. As for octopuses, no significant differences have been observed depending on the season, presenting a survival rate in spring of 76.0 ± 11.0 % compared to a percentage of 75.7 ± 4.3 % in autumn.

In the case of langoustines, the main biomarker of stress has been lactate (both in plasma and in muscle), as it is a by-product of glycolysis (glucose consumption) in anaerobic situations or high energy expenditure. The results have shown a complete physiological recovery six hours after the stress process. In the case of octopuses, glucose has turned out to be one of the most representative parameters. Carbohydrate consumption occurred during the first few hours after capture, regaining metabolic balance between six and twenty-four hours of recovery afterwards.

In the oceanographic campaign DESCARSEL 0918, the survival and recovery experiment of rays (Raja clavata) was carried out. Its survival was calculated after 24 hours of recovery from fishing and over 63 specimens caught in seven different sets. The mean survival rate obtained in the rays was 57.1 ± 8.3%. In the rays caught in the DESCARSEL campaign, the two parameters analyzed were lactate and glucose. In the case of lactate, the levels immediately after capture were significantly higher than those found after 24 hours of recovery (3.7 ± 0.08 mM, 2.6 ± 0.2 mM, respectively). However, glucose levels showed significantly lower levels after capture compared to levels recorded after 24 hours of recovery (2.8 ± 0.1 mM, 4.6 ± 0.3 mM). This indicates a consumption of carbohydrates immediately after the capture process.

An experiment was carried out on land with 45 catsharks (Scyliorhinus canicula), and it was observed that they recover after five hours of recovery. The ethological analysis of the rays (Raja clavata) determined that they need more than two hours to swim normally again. In the experiment, four phases of recovery in the behavior of the animals in the first two hours after trawling have been described: recovery of position, search for shelter, exploration of the bottom and exploration of the water column.