Crayfish stocks collapsed in Turkey in mid 1980's due to crayfish plague epidemics, with up to 25% survival in some cases. The collapsed stocks have then recovered slowly and commercial crayfish fishery was reinitiated gradually within a decade. We examined the prevalence of Aphanomyces astaci DNA in the narrow clawed crayfish (Astacus leptodactylus) collected from two Turkish lakes, Lake İznik and Hirfanlı Dam (N = 40 from both sites). The qPCR results, verified by conventional PCR and sequencing, indicated that nearly all sampled crayfish were A. astaci carries with some of them showing gross symptoms of infection, such as tissue erosion and melanisation, while some did not show any visible symptoms. The prevalence of A. astaci DNA was high in both stocks, being on the average 95% in both Lake İznik and Hirfanlı Dam. Our results show that these stocks are carries of A. astaci, but capable of forming productive stocks which indicates past and contemporary partial resistance adaptation in the host or virulence evolution in the A. astaci. RÉSUMÉ Des populations turques d'écrevisses à pattes grêles (Astacus leptodactylus) productives porteuses d'Aphanomyces astaci
Key-words:Aphanomyces astaci, susceptible signal crayfish, mortality, stress, moltingThe carrier status and possible elevated tolerance of the signal crayfish (Pacifastacus leniusculus) against the crayfish plague disease agent (Aphanomyces astaci) has been speculated for several decades. We studied experimentally the responses of the signal crayfish from two Finnish populations against the crayfish plague infection by using two crayfish plague isolates with differing virulences; the highly virulent PsI-isolate and the mid virulent As-isolate. The studied signal crayfish came from two origins: the wild Leppävirta population and the Raukola farmed population of mixed genetic background. Both test groups were infected with A. astaci isolates using the challenge of 10 000 spores mL −1 . The isolates were PsIPuujärvi (UEF8866-2) from Lake Puujärvi signal crayfish (year 2003) and As-Kivesjärvi (Evira6462/06) from Lake Kivesjärvi noble crayfish (year 2005 epidemic) in Finland. The crayfish were sampled prior to the experimental challenge with A. astaci to evaluate their A. astaci carrier status. The mortality, molting, feeding activity and other behavior of the crayfish were followed during the experiment. We observed increased mortality of the infected groups, related to the molting in some cases, and delayed molting. The impacts of the intense crayfish plague infection on the signal crayfish were clear and the studied populations showed differences in their reactions that are potentially explained by differing physiological conditions and different molt cycle phase. The results show that infection of both tested crayfish plague genotypes affects signal crayfish and is likely one of the main reasons behind losses among signal crayfish populations.
Summary Length–weight relationships were calculated for nine freshwater fish species belonging to two families using 1020 specimens from 15 water sources in the western part of Anatolia, Turkey. This study is the first reference on length–parameters for these species, eight of which are endemic, and with new maximum length records for three of the species.
-We studied the presence of possible Aphanomyces astaci infections in eight Turkish narrowclawed crayfish (Astacus leptodactylus) populations by analyzing the prevalence and genotypes of the disease agent A. astaci. The qPCR analyses revealed A. astaci infection in seven of the studied eight populations, with the agent level A2 or higher. The agent levels among the infected populations varied from A0 to A5, i.e., from negative to high level of infection, based on qPCR ranking. Based on the sequencing of the chitinase gene and the mitochondrial ribosomal rnnS and rnnL subunits, we detected both A (As) and B (PsI) haplogroups of A. astaci in our samples, with each of the studied populations being carriers of only one haplotype. The results confirm previous detections of A. astaci in Turkish narrow-clawed crayfish populations and reveal, that both A and B haplogroup A. astaci carriers exist widely in A. leptodactylus populations of Turkey.
This paper analyzes fish and fishery products consumption patterns and trends from five nationally representative crosssectional surveys' raw data conducted in 1994, 2003, 2004, 2005 and 2006 totalling of 77.744 householders in Turkey within the last 12 years period. In particular, we analysed the influences of different years, rural-urban locations, gender, age, income, education and occupation on fish and fishery products consumption in Turkey. According to results, the shares of total fish and fishery product consumption in total households' expenditure were overall 32% in Turkey within the last 12 years period. The results also showed that fish and fishery product consumption has been steady increasing in Turkey. There was a 5% difference between rural and urban location and while in average 8.7 TL in cities and 8.8 TL spent on fish in rural places. According to the results of this article, there is a statistically significant difference between socioeconomic factors and fish and fishery products consumption in Turkey.
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