Morphological abnormalities in gonads of the Baltic herring (Clupea harengus membras): Description of types and prevalence in the northern Baltic Sea

• Published in: Ambio Vol. 45; no. 2; pp. 205 - 214
• Main Authors: Rajasilta, Marjut, Elfving, Mikael, Hänninen, Jari, Laine, Päivi, Vuorinen, Ilppo, Paranko, Jorma
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer 01.03.2016; Springer Netherlands; Springer Nature B.V
• Subjects: Animal reproduction; Animals; Anthropogenic factors; Archipelagoes; Atmospheric Sciences; Clupea harengus; Clupea harengus membras; Earth and Environmental Science; Ecology; Ecosystems; Endocrine disruptors; Environment; Environmental conditions; Environmental Engineering/Biotechnology; Environmental Management; Environmental perception; Female; Finland - epidemiology; Fish; Fish Diseases - epidemiology; Fish Diseases - pathology; Fish populations; Fishes; Gonadal Disorders - epidemiology; Gonadal Disorders - pathology; Gonads; Gonads - pathology; Hermaphroditism; Hyperplasia; Male; Marine; Morphology; Physical Geography; Population; Prevalence; Reproductive health; Reproductive system; Spawning; Tubules; Baltic Sea; ANE, Finland; ANE, Baltic Sea; Reproduction; Herring; Malformation; Gonads; Baltic Sea
• ISSN: 0044-7447; 1654-7209
• DOI: 10.1007/s13280-015-0717-x

Due to heavy anthropogenic influence and variation of the environmental conditions in the Baltic Sea, reproductive disorders are becoming a major environmental concern. We show here an increasing prevalence of gonadal malformations in the Baltic herring (Clupea harengus membras), a key species of the Baltic ecosystem and important in commercial fishery. During 1987-2014, the spawning herring population in the Archipelago Sea (AS) (North Baltic Sea, Finland) was monitored annually and analyzed for gross morphology of the gonads [total number (n) of analyzed fish = 38 284]. Four different types of malformations were repeatedly found and named as asymmetric, rudimentary, segmented, and branched gonads, but also hermaphroditic gonads and miscellaneous (unidentified) disorders were recorded. In 2013, additional samplings (n of fish analyzed = 541) showed similar malformations in herring from the Bothnian Sea. In some gonad types, histological examination revealed disintegration of seminiferous tubules and hyperplasia of the interstitial tissue. In 2014, the overall prevalence of malformations was still relatively low in the AS (frequency = 0-3.4 %; n = 750) and had apparently minimal effect on population recruitment. However, an increasing trend in the time-series (GLM; F = 32.65; p < 0.001) and a significantly higher prevalence in the Bothnian Sea (frequency = 0.7-5.0 %; n = 541; χ² = 6.24; p < 0.05) suggest that gonadal malformations may become a new threat for fish in the Baltic Sea. The observed gonad atrophies may be due to environmental endocrine disruption; however, also other explanations may exist and potential explanations are discussed.