The aim of this study was to investigate PIT tagging effect on noble crayfish (Astacus astacus L.) survival depending crayfish size, sex, lack of limbs and burn spot disease PIT tagging experiment was carried out in Estonian University of Life Sciences department of aquaculture laboratory in 5. 01. 2012 to 18.04.2012. The experiment lasted 105 days. For this experiment 64 crayfish were caught from Valgevälja career. During acclimation period (23.09.2011 – 04.01.2012) nine specimens died that´ s why only 56 crayfish were involved in the experiment. After acclimation period all crayfish were measured for, total length (TL), carpace length (CL) and weight. Also the number of individuals registered as missing limbs and burn spot disease level was assigned (LH). 29 individuals were tagged (24 male and 5 female) (mean CL 53 and 46 mm) with 1,5 X 7 mm PIT tags whilst the other 27 (23 male and 4 female) (mean CL 49 and 45 mm) acted as a control group to examine post-tagging mortality levels. The tag was injected into muscle of the abdomen. All animals were marked with waterproof marker to assist in the identification of crayfish that were moulted. Tagged and control group were kept in two different tank (1 m3 ), filled with tap water, and provided with sections of plastic drainpipe for shelter. Water was changed at regular intervals (4–6 days). Crayfish were maintained at 18,5°C, a temperature at which they exhibit substantial feeding activity, with a light regime of 16 h: 8 h LD. Since during the test there was no moulting (presumably because the winter period, when crayfishes are less active), initial data were used in statistical analyses. Logistic regression models were structured according to Westhoff and Sievert (2013) defined by Hosmer and Lemeshow (2000) where π (Mortality) = e f / (1+e f ) where π (Mortality) equals the probability of tagging mortality and f equals β0 + β1 x1, where β0 equals the model intercept (constant), βi equals the parameter estimate, and xi equals carapace length or burn spot disease level of an individual. During experiment 12 animals died (11 male, 1 female) (mean CL 57 and 50 mm) in tagged group and in control group only five (4 male, 1 female) (mean CL 55 and 46 mm) animals died. Statistical analyses showed that between tagged and untagged animals, there was no significant difference in mean carapace length (CL) (t-test, p = 0,132). The relationship between CL and probability of crayfish mortality showed that probability of dying increase with growth. Previous studies have documented higher mortality rates in smaller crayfishes. Differences between previous and this studies may occur because of the burn spot disease. In tagged group there was nine infected crayfish, six of them were carrying disease level one, two of them disease level two and one of them had disease level three. In control group all five dead crayfish were infected, three of them were carrying disease level one and two of them disease level two. The relationship between burn spot disease level and probability of crayfish mortality showed that probability of dying increase with higher disease level. Since the sex ratio in both groups was 90% of males and 10 % of females, there was no statistical difference between sex and mortality. Although five crayfish in tagged group and two crayfish in control group had lost their appendages, there was no statistical difference between missing limb and mortality. Over the duration of the experiment, tag retention was 96,5 %. All tags except for one remained operational throughout the experiment and the tag identification number could be read by passing the reader unit over the tagged crayfish. Results of this study demonstrates that PIT tagging doesn’t affect crayfish mortality in laboratory more than untagged crayfish and therefore can recommend the use of PIT tags in crayfish research. To investigate PIT tagging effect on noble crayfish survival in the future the crayfishes should be healthy and the experiment conditions should be great to avoid stress.

Käesoleva magistritöö eesmärgiks oli hinnata mikrokiipide ehk PIT märgiste mõju jõevähi (Astacus astacus L.) ellujäävusele sõltuvalt vähi suurusest, soost, jäsemete puudumisest ja lapihaigusest. Kiibistamise mõju hindamiseks viidi läbi katse Eesti maaülikooli veterinaarmeditsiini ja loomakasvatuse instituudi vesiviljeluse osakonna laboris kahes 1 m3 suuruses basseinis perioodil 5. jaanuar 2012 kuni 18. aprill 2012. Katses osales 56 jõevähki, kes olid püütud Läänemaal asuvast Valgevälja karjäärist ning asustati kahte ühe m3 suurusesse basseini, mis olid varustatud varjepaikade ja filtritega. 29 jõevähki märgistati PIT mikrokiibiga (1,5 X 7 mm), mis süstiti spetsiaalse süstlaga läbi vähi kõhtmise poole tagakeha esimese lüli laka lihasesse. 27 vähki jäeti kontrollrühma, kellele kiipi ei sisestatud. Kestumise jälgimiseks märgistati nii katse- kui kontrollrühma vähkide seljakilbid veekindla korrektuurmarkeriga. Enne märgistamist määrati kõikide katses osalenud vähkide sugu, mõõdeti nii täispikkused (TP) kui seljakilbi pikkused (CL) ning kaaluti. Lisaks registreeriti puuduvate jäsemetega isendite arv ning määrati lapihaiguse aste. Vähke söödeti üle päeva põhjatoiduliste kalade söödaga. Märgistamiskatse tulemusena oli kiibiga märgistatud vähkide ellujäävus 58,6%, kiibistamata vähkidel 81,5%, kuid erinevus ei osutunud statistiliselt oluliseks (p = 0,084). Märgistamise ja ellujäävuse seos sõltuvalt vähi suurusest näitas, et vähi pikkuse kasvades suureneb vähkide surevuse tõenäosus, mis on vastupidine tulemus võrreldes varasemate sarnaste uuringute tulemustega. Käesoleva katse erinevus tulenes tõenäoliselt sellest, et vähid olid lapihaiged ning raskemini on nakatunud just suuremad isendid, kes kestuvad harvem. Seda näitas ka mõlema katserühma andmete alusel teostatud logistiline regressioonanalüüs, et suremistõenäosus suureneb oluliselt lapihaiguse kahjustuste ulatuse kasvades (p = 0,013), mistõttu võib järeldada, et lapihaigus oli ka üheks surevuse põhjuseks. Suremise tõenäosuse prognoosi lapihaiguse kahjustuste ulatuse alusel ei olnud vähkide väikese hulga tõttu võimalik läbi viia katse- ja kontrollrühmas eraldi. Seos märgistamise ja ellujäävuse vahel sõltuvalt vähi soost ei osutunud statistiliselt oluliseks, kuna katsegruppide emaste vähkide osakaal oli võrreldes isastega väiksem ning mõlemas katsegrupis suri võrdselt üks emane vähk. Märgistamise ja ellujäävuse seos sõltuvalt vähi puuduvatest jäsemetest ei näidanud samuti katsegruppide vahel olulist erinevust. Käesolev katse näitas, et jõevähkide märgistamine PIT märgistega ei mõjuta nende surevust sisetingimustes rohkem, kui märgistamata vähke. Kasutatud metoodikat võib soovitada vähkide märgistamiseks, kuid PIT märgiste mõju vähkide ellujäävusele tuleks hinnata ka tervetel jõevähkidel ning paremates pidamistingimustes, et välistada haiguse ja muude stressi tekitavate tegurite mõju.