Genetic origin and salinity history influence the reproductive success of Atlantic herring

Abstract

Atlantic herring populations inhabit environments ranging in salinity from fully marine to nearly freshwater, but their relative reproductive success in these respective environments remains unclear. We conducted factorial crossing experiments using parents from 3 wild populations associated with different salinity environments: the Baltic Sea (~6 psu), an inland brackish lake in Norway (Landvikvannet, ~16 psu), and the Atlantic (~30 to 35 psu). Further experiments used crosses within and between Atlantic purebreds and Atlantic/Baltic hybrids reared until first maturity at 3 yr of age. Crossing experiments were conducted at 6, 16 and 35 psu. Fertilization and hatching rates were estimated, and egg sizes were measured. Fertilization rates were highest at 16 psu for all combinations. The paternal genetic and salinity origin influenced fertilization rates at 6 and 35 psu, indicating a genetic adaptation to their original environment. Fertilization rates for males originating from 16 psu were low at 35 psu. Atlantic/Baltic hybrids had lower fertilization rates than Atlantic purebreds at 35 psu. Hatching rates were not influenced by any parental factors or salinity. Maternal effects and salinity influenced egg size. Atlantic females had significantly larger eggs than the Atlantic/Baltic hybrid females. For all genetic groups, egg size decreased with increasing salinity at incubation mainly due to osmotic effects. The observed lower fertilization success at salinities other than those of the parental fish habitat would have evolutionary consequences when herring colonize new habitats with different salinities or if interbreeding occurred between populations originating from different salinity habitats.

Respiration rates of herring larvae at different salinities, and effects of previous environmental history

“…Fertilizations were conducted at a salinity of 16 psu to achieve high fertilization rates (Berg et al 2019) and the ambient water temperature was approximately 10°C. Offspring from five parent pairs of autumn-spawning Baltic herring were incubated and co-reared together in the same tank at salinity of 16 psu and 10°C ( Figure 1).…”

Genetic response to human‐induced habitat changes in the marine environment: A century of evolution of European sprat in Landvikvannet, Norway

“…Landvik herring are considered as a self‐sustaining and somewhat stationary population, characterized by slower growth, smaller length at maturity, lower vertebral count, shorter life span, higher relative fecundity, and divergent genetic profiles compared to the migratory oceanic herring in other parts of the Norwegian waters (Eggers, 2013; Eggers et al., 2014; Silva et al., 2013). Meristic trait vertebral count is often used as a population identifier in herring (e.g., Berg et al., 2017; Mosegaard & Madsen, 1996; Rosenberg & Palmén, 1981), and the observation that vertebral count in Landvik herring is similar to that in herring populations in the brackish Western Baltic Sea has led to the hypothesis that Landvik was colonized by low salinity adapted herring of Western Baltic Sea origin (Berg et al., 2019; Eggers et al., 2014). In addition, factorial crossing experiments performed at a range of salinities ranging from 6 to 35 revealed adaptation of herring populations to their native salinity conditions and also that adaption to salinity is transmitted to the offspring within the following generation (Berg et al., 2019).…”

“…Meristic trait vertebral count is often used as a population identifier in herring (e.g., Berg et al., 2017; Mosegaard & Madsen, 1996; Rosenberg & Palmén, 1981), and the observation that vertebral count in Landvik herring is similar to that in herring populations in the brackish Western Baltic Sea has led to the hypothesis that Landvik was colonized by low salinity adapted herring of Western Baltic Sea origin (Berg et al., 2019; Eggers et al., 2014). In addition, factorial crossing experiments performed at a range of salinities ranging from 6 to 35 revealed adaptation of herring populations to their native salinity conditions and also that adaption to salinity is transmitted to the offspring within the following generation (Berg et al., 2019). In contrast to herring, which rely on a benthic spawning habitat for depositing eggs, sprat is a pelagic spawner.…”

Comparison of Otolith Microstructure of Herring Larvae and Sibling Adults Reared Under Identical Early Life Conditions

“…After net retrieval, euthanized herring were transported to the lab facilities in Bergen for the fertilization experiments. A short summary of the experimental setup will be presented, however, for a detailed experiment description see Berg et al (2018) and Berg et al (2019).…”

“…The growth of surviving fish was not influenced by the antibiotic treatment based on a comparison of growth rates before and after the treatment. After 3 years we thus had four experimental groups in the F1 progeny that were followed from larval life stages to adult life stages: Atlantic purebreds reared at 16 psu, Atlantic/Baltic hybrids reared at 16 psu, Atlantic purebreds reared at 35 psu and Atlantic/Baltic hybrids reared at 35 psu (Berg et al, 2019).…”