The poor state of cod in the Eastern Baltic is largely a consequence of biological changes in the stock during recent decades. One of several factors that may affect fish population dynamics is a high level of parasitic infection. Linear models were used to quantify the associations between two body condition factors, FCF and CF, and hepatosomatic index (HSI) with the level of nematode infection of cod liver. Parasitological analysis revealed the presence of nematodes representing the genera (the most abundant genus), and . The level of cod infection with larvae was markedly higher than reported in previous studies undertaken over the past few decades. Body condition factors and HSI significantly decreased with increasing infection density (IFD, defined as the number of nematodes per gram of cod liver tissue). However, the correlation between FCF and HSI was rather low, indicating that they may respond differently to environmental conditions. The decline in both body condition factors in females was significantly higher than in males. The IFD close to 5 in females and 9 in males was associated with a decline in CF below the threshold of lethality. The indices used reflect the amount of accumulated energy reserves in fish and an increase in IFD is one of the factors leading to a reduction in these reserves. Damage of liver tissue by nematodes may negatively affect the physiology of this organ and its capacity to store the necessary level of energy reserves.

中文翻译：

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波罗的海鳕鱼 (Gadus morhua) 肝脏中线虫的存在与宿主状况因子和肝体指数的下降有关

波罗的海东部的鳕鱼状况不佳很大程度上是近几十年来鱼类种群发生生物变化的结果。可能影响鱼类种群动态的几个因素之一是高水平的寄生虫感染。使用线性模型量化两个身体状况因素FCF和CF以及肝体指数（HSI）与鱼肝线虫感染水平之间的关联。寄生虫学分析揭示了代表该属（最丰富的属）的线虫的存在，并且。鳕鱼幼虫感染的水平明显高于过去几十年进行的研究报告。随着感染密度（IFD，定义为每克鳕鱼肝组织中的线虫数量）的增加，身体状况因素和 HSI 显着降低。然而，FCF 和 HSI 之间的相关性相当低，表明它们对环境条件的反应可能不同。女性这两项身体状况因素的下降幅度均显着高于男性。女性的 IFD 接近 5，男性的 IFD 接近 9，与 CF 下降到致死阈值以下有关。使用的指数反映了鱼类积累的能量储备量，IFD 的增加是导致这些储备减少的因素之一。线虫对肝组织的损害可能会对该器官的生理机能及其储存必要能量储备的能力产生负面影响。