Female ovarian abnormalities and reproductive failure of autumn-spawning herring (Clupea harengus membras) in the Baltic Sea

Abstract

Fecundity and reproductive potential are important factors to be considered in evaluating trajectories and demographic predictions of fish populations. Therefore, characterizing the nature and quantifying the extent of any reproductive failure should be considered in fisheries studies. Here, we describe morphological changes in developed ovaries of autumn-spawning herring (Clupea harengus membras) caught in the northern Baltic Sea and evaluate the magnitude of this phenomenon during 3 consecutive years. Visibly, abnormal ovaries were histologically characterized by irregular-shaped oocytes in a vitellogenic or final maturation stage with coagulative necrosis and liquefaction of the yolk sphere, degraded follicle membranes, and fibrinous adhesion among oocytes. Such degeneration is presumed to cause complete infertility in the fish. The frequency of fish with abnormal ovaries varied annually between 10 and 15% among all females sampled. However, specific sampling events showed up to 90% females with abnormal gonads. The specific cause of this abnormality remains unknown; however, prevalence was associated with unfavourable environmental conditions encountered before spawning. Thus, ovarian abnormality was positively related to water temperatures, with the highest level found at ≥15°C and negatively related to the frequency of strong winds. The frequency of occurrence of abnormal gonads decreased with the progression of spawning from August to October. The observed abnormality and associated spawning failure will negatively affect the realized fecundity of autumn herring in the Baltic Sea and may act as a limiting factor for recovery of the stock, which has experienced profound depression during the last three decades.

A chromosome-level assembly of the Atlantic herring – detection of a supergene and other signals of selection

“…spawning North Sea herring (NS in Figure 6b). This strong genetic differentiation 10 is never observed at selectively neutral loci among the populations included in 11 this analysis (Lamichhaney et al, 2017;Martinez Barrio et al, 2016), which 12 provide conclusive evidence that this supergene polymorphism must be under 13 selection, possibly related to temperature at spawning, which is known to be a 14 major stressor for the southernmost and high temperature exposed herring 15 populations (Ojaveer et al, 2015;Peck et al, 2012). 16…”

Effect of Environmental Pollution on Gonads Histology of the Nile Tilapia, Oreochromis niloticus from Lake Manzala, Egypt

“…The analysis of reproductive functions is a key factor in determining the dynamics of fish populations (Mekkawy and Hassan, 2011;Ojaveer et al, 2015). The presence of pollutants is one of many environmental factors that can result in a dangerously compromised fish reproduction system.…”

Evidence from the past: exploitation as cause of commercial extinction of autumn-spawning herring in the Gulf of Riga, Baltic Sea

“…The high level of adult and juvenile exploitation apparently dominated the direct potential impacts of a variety of environmental factors that could also have influenced population dynamics. For example, winter severity and autumn-winter wind strength have been shown to influence year-class strength , and warm (> 15°C) water temperatures in late summer may cause female reproduction failure in autumn spawning herring (Ojaveer et al, 2015). In addition, given that spawning habitat for autumn spawning herring is deeper than that for spring spawning herring , the autumn stock may be more vulnerable to eutrophication-related anoxia events.…”