Biocomplexity in a highly migratory pelagic marine fish, Atlantic herring

Abstract

The existence of biologically differentiated populations has been credited with a major role in conferring sustainability and in buffering overall productivity of anadromous fish population complexes where evidence for spatial structure is uncontroversial. Here, we describe evidence of correlated genetic and life history (spawning season linked to spawning location) differentiation in an abundant and highly migratory pelagic fish, Atlantic herring, Clupea harengus, in the North Sea (NS) and adjacent areas. The existence of genetically and phenotypically diverse stocks in this region despite intense seasonal mixing strongly implicates natal homing in this species. Based on information from genetic markers and otolith morphology, we estimate the proportional contribution by NS, Skagerrak (SKG) and Kattegat and western Baltic (WBS) fish to mixed aggregations targeted by the NS fishery. We use these estimates to identify spatial and temporal differences in life history (migratory behaviour) and habitat use among genetically differentiated migratory populations that mix seasonally. Our study suggests the existence of more complex patterns of intraspecific diversity than was previously recognized. Sustainability may be compromised if such complex patterns are reduced through generalized management (e.g. area closures) that overlooks population differences in spatial use throughout the life cycle.

Detecting population structure in a high gene-flow species, Atlantic herring (Clupea harengus): direct, simultaneous evaluation of neutral vs putatively selected loci

“…Using the microsatellite data for the same samples collected at Berwick and Tj me as in this study, as well as several other samples, Ruzzante et al (2006) showed that herring collected at Rü gen in the southwestern Baltic is clearly distinct from the populations in the North Sea and Skagerrak. In this study, the differentiation estimated with neutral microsatellites was stable over Abbreviations: AMOVA, analysis of molecular variance; MHC, major histocompatibility complex; mtDNA, mitochondrial DNA.…”

“…However, as long as selection pressure is temporally stable (decades-centuries), genetic markers influenced by selection, such as Cpa112, can be of use in detecting population structure on ecological time scales, where neutral loci have not yet diverged substantially. Selected loci may be particularly useful in genetic stock identification based on individual assignment and as markers for population origin in mixed-stock analysis (see Nielsen et al, 2009a, p. 3136), for example, MHC in Pacific sockeye salmon (Beacham et al, 2005), the pantophysin locus in mixed stocks of coastal and oceanic cod in Lofoten, northern Norway (Wennevik et al, 2008) and Cpa112 in mixed-stock analysis of herring in the Skagerrak (Ruzzante et al, 2006). It may be preferable to use selection-influenced genetic markers with known function (Hoffmann and Willi, 2008), or with at least some knowledge of the nature of the selection pressure, for example, hemoglobin (Andersen et al, 2009), genes involved in osmoregulation (Larsen et al, 2008) and depth adaptation (Á rnason et al, 2009).…”

“…Recent genetic investigations using microsatellite DNA and allozyme markers have found little differentiation among spatially discrete populations in the North Sea, but concordant divergence between the Baltic and North Sea populations Mariani et al, 2005;Larsson et al, 2007Larsson et al, , 2010. Genetic mixed-stock analyses show that coastal Skagerrak is used as a nursery both for the Baltic and North Sea spawning populations (Ruzzante et al, 2006). Earlier studies of population structure in the NE Atlantic using mtDNA have generally indicated little divergence among the populations (Dahle and Eriksen, 1990).…”

Fine-scale spatial and temporal genetic structure of Atlantic cod off the Atlantic coast of the USA

“…Abbreviated sample names are defined in Table 1 life-cycle diversity in fish (e.g. Ruzzante et al 2006, Kerr et al 2009b). Gene flow is not only a function of adult behaviors, but also of egg and larval dispersal.…”

The Future of Baltic Sea Populations: Local Extinction or Evolutionary Rescue?

“…An important consequence of species being divided into locally adapted populations that may have key roles in their local ecosystem is that an extinct local population may not easily be replaced by recruits from other areas. Indirect support for such a conclusion is found in species where extensive mixing of populations occurs during some life stage without break down of the discrete population structure-a phenomenon sometimes referred to as biocomplexity (Ruzzante et al 2006;Schindler et al 2010).…”