SINTEF Fiskeri og havbruk AS

Quality of gillnetted coastal cod QualiFish day 2016

19.04.2016Guro Møen Tveit

SINTEF Fiskeri og havbruk AS 2

Contents

• Background• Experimental setup • Results

– Catch damages– Fillet evaluation

• Conclusion• Communication and dissemination

SINTEF Fiskeri og havbruk AS

• This experiment is a part of work package one in the QualiFish project working with technologies for improved catch handling.

• Task 1.1 Case study of the coastal fleet: improve catch quality and reduce catch damages of net caught fish by changing net-material, investigating optimal fishing time, etc. to improve quality and reduce damages caused by the net.

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Work package 1 (WP1)

SINTEF Fiskeri og havbruk AS

Background

• Gillnets are one of the most important fishing tools in the fisheries of North Atlantic cod and coastal cod in Norway. However, there is a lack of available studies on the effect gillnet material and available technologies have on catch quality.

• Unsatisfactory quality of gillnetted cod has long been a challenge in the whitefish industry, and some in the fish processing industry have stopped or reduced their purchases of gillnetted fish.

• Where does the quality deterioration arise? Is it during the catching procedure? During the handling of the fish? Or, perhaps during the processing on land? It should be the quality of the catch and not the catching method that should influence the buyers.

Figure 1. Hauling of monofilament gillnets with a toothed net stopper (left).Multimono net material (middle) and monofilament net material (right).

SINTEF Fiskeri og havbruk AS

Figure 2: Seasonal variations in the Norwegian fleets and cod landings (Standal & Hersoug, 2015).

SINTEF Fiskeri og havbruk AS

• The experiments were conducted at Husøy, Senja in January this year.• During the experiment, hauling with a traditional toothed net stopper was compared

with a rubberized vertical roller, and monfilament net material (0.6 mm) was compared with the somewhat thicker and softer multimono net material (1.5 mm*6).

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Experimental setup I

Multimono net material Monofilament

net material

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Experimental setup II

• For five consecutive days four gillnet chains, each consisting of 25 nets, were cast in pairs in two different areas at a depth of 30 meters, and left to soak for 24 hours before hauling.

• During five days of fishing coastal cod (30 866 kg) (our target species), saithe/pollock (9 876 kg) (Pollachius virens) and haddock (591 kg) (Melanogrammus aeglefinus) and minor volumes of other species were caught.

• A total of 201 large cod consisting of 59% females and 41% males with a weight around 8-10 kg and a length of around 1 meter were hauled on board.

SINTEF Fiskeri og havbruk AS

• The mortality of the catch evaluated immediately after the catches were brought on board was 30.5% for all treatments. Additionally 23.9% of the catch, corresponding to 75.4% of the dead fish, was in rigor at time of evaluation.

• The mortality rate varied within the range 17.1% to 45.5% for the different treatments, where fish caught with multifilament gillnets had the lowest mortality while monofilament gillnets had the highest.

• In spite of the mortality rates, only some of the dead fish exhibited the distinct dead-fish character.

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Mortality

SINTEF Fiskeri og havbruk AS

• The results showed that there were very little or no difference in the quality of round fish between the cod caught with the different net materials or the different hauling techniques.

• Gear injuries: 95% of the entire catch exhibited gear injuries.• Scale-loss/rubbing: was found on 88% of the catch. • Pressure injuries: only 7% of the catch exhibited pressure injuries.• Bruises: 92% of the catch has visible bruising.

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Catch damages

SINTEF Fiskeri og havbruk AS

Fin damages

0

20

40

60

80

100

Dorsal fins Caudal fin Anal fins Pectorial fins Ventral fins

Bloo

d on

fins

(%)

Blood on fin %

Net stopper Vertical roller Monofil Multimono

0

20

40

60

80

100

Dorsal fins Caudal fin Anal fins Pectorial fins Ventral fins

Fin

split

(%)

Fin split %

Net stopper Vertical roller Monofil Multimono

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Fillet evaluation - Color

Figure 4: Comparison of cod fillets cut on board: worst case (A) and best case (B), and worst (C) and best case (D) fillets after 6 days of cold storage.

A

B

C

D

On board After cold storage

SINTEF Fiskeri og havbruk AS

Conclusions

• The results showed that there were very little or no difference in the quality of round fish between the cod caught with the different net and hauling constructions.

• Cod caught with multimono net material did exhibit a higher survival rate compared to the fish caught with the monofilament gillnets.

• The fillets from the multimono nets gave lighter and whiter fillets compared to the monofilament nets.

• Over all the fillets were white and of a good quality. • The results are still being processed, and it is expected that an article on the

experiments will be published next year.

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Communication and dissemination

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Thank you for your attention !

Thank you for you attention

Thank you for your attention