Friday, 12 February 2021

Optimizing the Norway lobster catch


Notus has developed a sensor to respond to the detection need of the Norway lobster fishing fleet and to know, in real time, if there is a sufficiently profitable amount of the target species in the area where it is trawling or if, On the contrary, the presence of this is so scarce that it is not worthwhile to continue working in that area, which significantly reduces fuel consumption in relation to the result obtained in the set. The entry into force of the landing obligation and the evolution of stocks in light of climate change has led the company to develop this sensor. 

"One of the measures proposed to reduce the capture of small fish, species with depleted quota and the capture of unwanted species in the trawl fishery is the use of the Crayfish Catch Sensor (Notus Echo) in the Swedish Grid" , informs the company.

"The preliminary results have been highly satisfactory both in the red prawn and Norway lobster fisheries," explains the company.

The use of Swedish Grid or Selector Grid, with vertical bars 35 mm apart and a 15 cm high opening at the bottom with a 70 mm cod-end, has been tested with very satisfactory results when combined with panels. square mesh (SMP) or SENTRA flakes.

Initially developed for the shrimp trawl fishery off the US west coast, it has been introduced with increasing success to the Norway lobster fishery in Ireland or Denmark or to the boreal shrimp fishery in Greenland .

In recent weeks, tests of the Echo de Notus Sensor have been carried out on board the M / P trawler “La GeltrĂș”, based in Vilanova i la GeltrĂș (Barcelona). For the operation of the Echo sensor, a selector grid adapted to the shape and dimensions of the net was required to be placed at the end of the rig sleeve. This grid shows large windows to allow the passage of companion species, both demersal and benthic, present in the fishing area and that are of high added value, in addition to having a part in the form of a grid necessary for the detection of the Red Shrimp in real time. Said grid is made of aluminium with a 50 mm spacing between the bars, avoiding at all times that the entire grid structure causes the cod-end meshes to close below the legal measure of 40 mm. The sensor was placed in different positions on the grid to determine the optimal sensitivity.

High performances have been achieved when the mark of the Echo sensor has been followed by turning around when it has stopped marking in a certain cast.

Cameras using wide-angle fields were placed in front of the grid to help define the results of the sensors in use . All video recordings were evaluated at sea to confirm if the prawns were hitting the grate. The camera and grid angles were readjusted as required throughout the tests.

The grid was initially placed in the lower part of the sleeve of the net. With the observations of the camera and the marks registered by the Echo sensor, it was determined that the best position of the grid is at the top since in this way the detection of crabs or other species that are captured as companion fauna is avoided. The sensitivity to noise of the Echo sensor is set to the maximum "since the shrimp produces a very slight noise as it passes through the grate", highlights the company.

Preliminary results have been highly satisfactory for both red prawn and Norway lobster fisheries," explains the company. Operational efficiency is substantially improved in real time by confirming the presence or absence of shrimp or Norway lobster during trawling. High performances have been achieved when the mark of the Echo sensor has been followed by turning around when it has stopped marking in a certain cast. "The calibration of the sensitivity of the system is adequate and the only problem that can be represented for a generalized use in the fleet is the use of the grid, essential for the operation and placement of the Echo sensor," adds the company. The design of the grid, with large windows in the lower part, allows companion species to pass through, so the capture of these species is not reduced, which helps to increase the value of the total catch.

This information was originally published in the Electronic Equipment special of the February issue of IP magazine . Access the full number 2166 here .


Demersal fish, Norway lobster (Nephrops Norvegicus) and red prawn (Aristeous Antennatus) are the most valuable species caught by the Spanish fleet, both in the Atlantic and in the Mediterranean. Optimising rig setup can be of great help.

In its 2018 report "Impacts of climate change on fisheries and aquaculture", FAO highlights how changing the type of fishing gear from single to multiple gear with two or four nets in the crustacean fishery results in significant fuel savings . Multiple nets are the types of nets most commonly used in the fishery for crustaceans such as Norway lobster, prawn or shrimp in most of the world except for Spain, as twin-nets are prohibited. The FAO report also describes how fisheries instrumentation development can improve energy efficiency in well-managed fisheries. Detection equipment and catch sensors also reduce fishing time and fuel consumption. "Even so, their use has traditionally been restricted to catching fish rather than catching crustacean species since they are more difficult to detect and discern," the company indicates.

In February 2020 the Irish Fishery Product Development Agency (BIM) published the “ Guide on Technical Solutions to Reduce Unwanted catches”. The landing obligation is initially implemented through discard plans that have very detailed requirements for demersal fisheries in North Western waters. These include survival and minimum exemptions that allow continued discards and gear measures aimed at avoiding unwanted catches during fishing. The new measures on gear are also implemented through other legislation, such as corrective measures under the EU Annual Regulations on Fishing Possibilities.

Many of the solutions developed in Ireland are included in this EU legislation which greatly helps with industry adoption and implementation.