Negativni utjecaj tovilišta tuna na okoliš

undergraduate thesis

• Title (english): Negative impact of tuna cages on environment
• Author: Lovro Ogresta
• Mentor: Petar Kružić (mentor)
• Granter: University of Zagreb; Faculty of Science; (Department of Biology); Zagreb
• Defense date and country: 2018, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Biology

Abstract

Tovilišta tuna su se razvila i proširila svijetom u kratkom periodu te su izgurala klasični
ribolov kao večinski izvor tune na tržištu. Kao jednoj od najunosnijih i globalno raširenih
grana akvakulture sve se više pažnje pridaodaje njihovom utjecaju na okoliš. Iako se za rad i
održavanje ribljih kaveza ne koriste nikakve toksične tvari njihov negativni utjecaj na okoliš
proizlazi iz velike količine organskog otpada u obliku ribljeg izmeta i ostataka hrane.
Područja oko kaveza su opčenito okarakterizirana povišenom bioprodukcijom i smanjenom
koncentracijom kisika, a utjecaj ribljih kaveza se može osjetiti i do kilometar udaljenosti.
Pronađene su povišene koncentracije otopljenog dušika i ugljika, a u sedimentu se redovito
nalaze povečane količine fosfora i sulfatnih iona kao rezultat rada bakterija u anoksičnim
uvjetima. Osim u sedimentu anoksični uvjeti mogu zavladati i u moru u slučaju da su struje
slabe ili nepostojeće, a da je opterečenje dovoljno veliko što može uzrokovati velike ekološke
štete. Takve promjene u okolišu imaju snažan utjecaj na lokalnu zajednicu, mjenjajući njezin
sastav, a mogu i u potpunosti izbrisati pojedine vrste. Jedan od najugroženijih ekosustava je
onaj koji ovisi o primarnoj produkciji posedonije (Posidonia oceanica) koja je izrazito
osjetljiva na promjene u sedimentu te negativno reagira na njih i na udaljenosti od 400 m od
ribljih kaveza. Povlačenjem posedonije stanište gubi velik broj mladih riba i člankonožaca
koje u livadama posidonije pronalaze utočište i hranu

Abstract (english)

Tuna cages developed and spread over the world in a short period of time and replaced
classical fishing as the major source of tuna in the market. As one of the most profitable and
globaly spred branches of aquaculture, it's impact on the environment is being increasingly
called attention to. Even though no toxic substences are used to maintain fish cages, they
produce large amounts of organic waste in the form of fish excrement and food leftovers, thus
leading to a negative environmental impact. The areas around cages are generally
characterised by increased levels of bioproduction and reduced concentrations of oxygen, an
impact of fish cages that can be felt up to a kilometer away. Elevated concentrations of
nitrogen and carbon have also been found in the water. Increased amounts of phophorus and
sulfate ions, as a result of bacterial function in anaerobic conditions, are often found in the
sediment. Other than the sediment, anaerobic conditions can occur in the sea in the case of
currents being week or non-existing and the organic load being high enough, which can cause
great environmental dammage. This sort of changes in the environment have a strong impact
on the local biological community, changing it's composition and sometimes even erasing
certain species altogether. One of the most endangered ecosystems are ones that depend on
primary production of posidonia (Posidonia organica) which is extreemly sensitive to
changes in the sendiment and reacts badly to them even at a distance of 400 meters from a
fish cage. The retreat of posidonia means that a number of small fish and arthropods living in
the plains of posidonia will have lost their source of food and shelter.

• Keywords: tovilišta tuna; okoliš
• Language: croatian
• URN:NBN: urn:nbn:hr:217:739970
• Study programme: Title: Environmental Sciences; Study programme type: university; Study level: undergraduate; Academic / professional title: sveučilišni/a prvostupnik/prvostupnica (baccalaureus/baccalaurea) struke znanosti o okolišu (sveučilišni/a prvostupnik/prvostupnica (baccalaureus/baccalaurea) struke znanosti o okolišu)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2018-08-29 08:39:07