March | April 2013

Escapes primarily caused by equipment failure

The International magazine for the aquaculture feed industry

International Aquafeed is published six times a year by Perendale Publishers Ltd of the United Kingdom.All data is published in good faith, based on information received, and while every care is taken to prevent inaccuracies, the publishers accept no liability for any errors or omissions or for the consequences of action taken on the basis of information published. ©Copyright 2013 Perendale Publishers Ltd. All rights reserved. No part of this publication may be reproduced in any form or by any means without prior permission of the copyright owner. Printed by Perendale Publishers Ltd. ISSN: 1464-0058

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24 | InternAtIonAl AquAFeed | March-April 2013

Equipment failure or operationalerrorsarebehindthreeoutoffourfarmedsalmonescapes.Twooutofthree escapes are due to holes in

seacagenetsaccordingtoanewstudy.

Researchers working on the SECUREproject (Securing fish – farming technologyandoperationstoreduceescapes)haveana-lysedallescape incidentsbetween2006and2009reportedbyNorwegianfishfarms.Theirefforts provide the industry and researcherswith new insights into the factors leading tolossatNorwegianproductionfacilities.

Structural failures most commonEquipmentfailureordamage isthemajor

factor behind the escape of farmed salmon.Figures from theSECUREproject show that68 percent of escapes occurred because ofstructural failure. An additional 8 percentwere able to escape due to human errorduringoperations.Elevenpercentofescapestook place from land-based facilities and anequalpercentageescapedduetoexternalfac-tors.All inall, the researchershave revealedclearexplanationsfor96percentofthetotalescapesreportedfrom2006to2009.

Factors changing over time“Commonstructuralfailuresincludeprob-

lems with mooring lines, collapsed floatingcollarsandholestorn inthenettingofaseacage. Badweather is another factor contrib-uting to structural failure and escape. Wehavealsodocumentedincidentsofautomaticfeedingdevices loosenandcausingdamage,”says Østen Jensen, research manager withSINTEFFisheriesandAquacultureandprojectmanageroftheSECUREproject.

The escape incident reports reveal thatequipment suppliers and fish farmers havemanaged to solve some of the equipmentproblemsthatpreviouslyledtoahighnumberofescapes.

“Escapes caused by mooring or floatingcollar failure have become more and morerare.The greatest challengenow facingpro-ducersofsalmonandtroutishowtopreventwear and tear to the netting. Holes formedfromchafingcontactbetweenthenetandthesinker tubechainwereresponsible formorethan 50 percent of total escapees between2008and2010,”DrJensensays.

Fewer large-scale escape eventsOperationalerrorduringactivitiessuchas

delousingormaintenance,combinedwithfishtransfer, account for close to 20 percent oftheescapefigures.Thelastlarge-scalesalmonescapeevent, inwhich175,000 fishescapedaproductionfacilityinTrøndelag,occurredinconnectionwithdelousing.

“Large-scaleescapeeventsinwhichmorethan 10,000 fish are involved comprise 19percentofthetotalnumberofescapesduringthe period studied. As much as 91 percentof all fish that escaped can be attributed tolarge-scaleevents,”saysDrJensen.

The reduction in the number of largeescape events is the most significant fac-tor behind the substantial reduction in thenumberofproductionsalmonescapeesfrom2006to2009.

Characteristics of fish likely to escape

Behaviouraldifferencesamongthevariousspeciesoffarmedfishalsoplayintotheriskofescape.Whereasonlyonepercentofsalmon

escapescanbeattributedtobiologicalfactors,oneoutofeveryfourescapedfarmedcodgotoutthroughholesinthenetscausedeitherbypredatorsorthecodthemselves.

“Incontrasttosalmonandtrout,codwilloften bite the netting and tear the netwall.The cod also display more interest in suchholesandarefarmoreeagerthansalmonortrouttotrytoswimthroughthem,”addsDrJensen.

The Houdinis of the seaCod are better escape artists than other

species of production fish, opting to swimthroughobstaclesratherthanaroundthem.

AspartoftheSECUREproject,research-ers at Norwegian Institute of Food, Fisheryand Aquaculture (Nofima) have analysedthe behavioural characteristics of cod whichmakethemmorelikelytoescapethanotherproduction species. Using controlled experi-ments, researchers have studied how theybehaveinseacages.

Codconstantlybiteandnibbleonthenetthreads, showinggreat interest in investigat-ing anything that appears unnatural to theirenvironment. This affects how net repairshould be approached at cod-productionfacilities. Repairs are most effective whencolours and shapes of the repaired nettingconformtotheoriginal.Theendsofthreadsneedtobeaffixedsothattherepairwillnotdeviate in appearance from the rest of thenetting.

Improved reportingFish farmers are required to report all

escapeevents to theDirectorateofFisheries.Jensensaysthatescape incidentreportinghasimproved substantially since the Norwegian

ESCAPESprimarily caused by equipment failure

by Torkil Marsdal Hanssen, Norway

26 | InternAtIonAl AquAFeed | March-April 2013

FEATURE

March-April 2013 | InternAtIonAl AquAFeed | 27

AquacultureEscapesCommission(AEC)intro-ducedanotificationtemplatefiveyearsago.

Placing responsibility on suppliersTwoproblemareasstandoutintheefforts

to reduce the risk of escapes in Norwegianaquaculture. Jensen believes that both canbe solved by the suppliers of aquacultureequipment.

“If the aquaculture industry is ever goingtorealisticallyrealiseitsvisionofzeroescapesfrom sea-based production facilities, it mustsolve two big challenges. The first is thatweightingsystemscurrentlyinusetomaintainthe shape and volume of the net pens leadtowearand tear in thenetting.The secondis finding ways to decrease the incidence ofoperational–orhuman–error.”

Solutions can be developedDr Jensen points out that the key to

solving both challenges can be found in thesupplierindustry.

“Improvedproductdesignandprocedurescanmitigateand, inpart,preventbothwearandtearaswellashumanerrorduringopera-tionsatsea.Muchoftheequipmentinuseinsea-based facilities shouldbe redesignedandsimplifiedtomakeitdifficultorimpossibletouse incorrectly. Under the SECURE projectwehaveacquired theknowledgeneeded todevelop better and more secure solutions.Thenextstepisuptothesuppliers.”

Suppliers have already begun applyingthe documented findings from the SECUREproject to test new solutions. The ResearchCouncilofNorwayallocated funding to twonewresearchprojectsthisyear(Towardssus-tainable fish farming at exposedmarine sites[SUSTAINFARMEX2011-2014]andExposedFarming)thathavecarriedoutmodellingtestsusingnetswithintegratedsinkertubes.

Certification scheme improves safety

The SECURE project has documented anumberof factorssignificant foravoidingnetabrasionandtearing:• Insufficient weighting of net-cages, use

of exceedingly large nets, sea-currentconditions and biofouling lead to netdeformation and risk of abrasion andtearing.

• Washing nets by machine reduces thestrengthofnetthreadsby10-20percentafter4-5washings.

• Attachingthesinkertubetothenethasproven to be a more secure solutionthanusingslidingconnectors.

• Conic net pens create more distancebetweenthenetandthechain,reducingtheriskofabrasionandtearing.Inspiteof this, the majority of net pens arecurrentlycylindricalinshape.

“Fish producers are able to buy freely

on the market and can purchase nets andfloating collars separately. It is by no meansautomatic that the net chosen will suit theselected floating collarwhenassembled.Weneedtohaveamoreintegratedapproachtothe design of fish-farming systems to ensurethatcomponentsarecompatible,”explainsDrJensen,whobelievestheintroductionoffacil-itycertificationisastepintherightdirection.

Providing input for regulations

Asof January1, 2013, all fish-productionfacili-ties in Norwaymust have cer-tification statingthatthefacilityisusingcompatiblecomponents.

“TheSECUREprojecthas providedknowledge ofimportance tothe design ofregulations thatthat will formthe basis forfacility certifica-tion, amongother things.We have seenthat the layoutofafacilitycom-binedwithwavesize can haveunforeseen con-sequences. Thehighest wave

doesnotalwayscarrythegreatestforce.Wehave found examples where a low-crestedwaveexertsmuchgreater forceona facilitythan a steep wave. Twice the force is notunusual,andthisshouldobviouslybeincorpo-ratedintothespecificationsforthedesignanddimensions of a production facility,” Jensenconcludes.

More information: www.forskningsradet.no

26 | InternAtIonAl AquAFeed | March-April 2013 March-April 2013 | InternAtIonAl AquAFeed | 27

FEATURE

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Need for novel sources

In order to reducedependence on fish oil, sig-nificant breakthroughs have

occurred over the past fewyearsinreplacingitwithplantoils.Bysubstitutingfeedswith

plantoils,italsoservestoreducecostsduetothefactthatvegeta-

bleoilshavesteadilyincreasingproduc-tion, high availability and better economicvalue.Several studieshavebeencarriedout

toinvestigatecertainvegetableoilsaspos-siblesustainablepartialsubstitutesforfishoils incompoundedfish feeds.Themost

commonvegetableoilsusedforfishfeedpro-ductionhavebeensoybean,linseed,rapeseed,sunflower,palmoilandoliveoil.

Soybeanand rapeseedoil areconsideredpossible alternative lipid sources for salmo-nids, freshwater and marine fish since theyare rich in PUFAs, especially linoleic (18:2ω−6)andoleicacid(18:1ω−9),butdevoidof n-3 PUFA. However, in some cases, fishoil substitution by 60 percent rapeseed oilhas been found to decrease European seabass (Dicentrarchus labrax) growth. Soybeanoil appears to be a better plant lipid sourceregarding gilthead seabream (Sparus aurata)growth while considerable savings in feedcostscouldbeachievedifitcouldbeusedas

a partial dietary substitute for fish oil withincompoundfeeds.Thesameistrueoflinseedoil and rapeseed oil, although to a lesserextent.

Furthermore,theuseofpalmoilindietsofAtlantic salmonand rainbow trouthas given

growthandfeedutilizationefficiencycompa-rabletofishfedwithequivalent levelsof fishoil. Olive oil could also be used as a partialsubstitute for dietary fish oil in Europeansea bass culture, during growth out phase,Atlantic salmon (salmo salar) and rainbowtrout(Oncorhynchus mykiss)withdatashowingsimilargrowthratestotheoneswhenfishwasfedon100percentfishoildiet.Allthesestud-

ieshavebeenrecentlyreviewed(NasopoulouandZabetakis,2012).

New, alternative and in a way ‘non-orthodox’, sources of lipids need to beidentified and valorised in order to achievesustainableproductionof fish feedsand thus

enablingthefurtherdevelopmentofaquacul-tureapplications.Suchpromisinglipidsourcesarevegetableoils(VO).TheuseofVObasedaquafeedshassomestrongadvantages.Olivepomace (OP) and olive pomace oil (OPO)are natural by-products of olive oil produc-tion, which contain micro constituents withatheroprotective(substances)activitysuchasPAF-inhibitorsandphenolic/polyphenolicmol-

Figure 2: Representative optic micrographs x 100 of aortic wall sections stained with haematoxylin and eosin from the two experimental groups, where atherosclerotic

lesions appear as foam cells (↑). (A) Group A (atherogenic diet); (B) Group B (atherogenic diet enriched with sea bream polar lipids) (adopted from Nasopoulou et

al., 2010). Copyright, “Food Chemistry” Elsevier

B)

22 | InternAtIonAl AquAFeed | March-April 2013 March-April 2013 | InternAtIonAl AquAFeed | 23

FEATURE

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