Inferring spatial structure from population genetics and spatial synchrony in demography of Baltic Sea fishes: implications for management

Abstract

The spatial structure of species is important for their dynamics and evolution, but also for management and conservation. There are numerous ways of inferring spatial structures, and information from multiple methods is becoming more common to examine how different processes shape the spatial structures of species to improve fish management. Here, we investigate the spatial structure of a suite of Baltic Sea fish species based on the following: (i) spatial (presumably neutral) genetic differentiation, reviewed from the literature, and (ii) spatial synchrony in abundance changes from time series of fishery‐independent surveys, which we currently find to be underused given the amount of data available. For each of these two methods, species were classified as having a distinct, continuous or no/weak spatial structure. In addition, based on each source of information, we estimated the spatial scale of management units for species. The results show that only among species confined to the coastal zone the two sources of information yielded a congruence of the spatial structure (displaying a continuous spatial structure). In contrast, offshore species show weak spatial genetic structure but stronger spatial structure of synchrony in abundance. Based on this, we suggest that population genetic structure and synchrony in abundance should be used as complementary information as they reflect different spatial processes and suggest that management actions should differ with respect to scale depending on the management targets applied. We propose similar analysis should be applied to areas outside the Baltic Sea, and other stock identification methods, to improve management of fish resources.

Spatial scaling of population synchrony in marine fish depends on their life history

“…This could be influenced by several factors, but movement dynamics is likely to be a major driver. Homing behaviour could be affecting the spatial synchrony of changes in abundance (Östman et al ), and is also a population characteristic that is not associated with life history. For example, all species studied here migrate annually to spawning grounds and feeding grounds (Olsen et al ).…”

Past and Current Trends of Coastal Predatory Fish in the Baltic Sea with a Focus on Perch, Pike, and Pikeperch

“…Data are hence not directly comparable across areas, and common analysis is currently limited to track changes over time in the relative abundances of the species and community elements in each area, as done in this review. Because coastal fish communities also are local in their appearance and response to environmental conditions [23][24][25][26][27]32], generic thresholds for good status has to date not been established [22]. Moreover, with few exceptions, the data available do not allow for full analytical assessments models, as are traditionally used for fish stock assessments, but see [33].…”

“…Pike have a similar distribution and range as perch, but occur naturally in much lower densities in most areas. Populations of obligate coastal predatory species such as perch, pike, pikeperch, and burbot are rather local in their appearance and response to environmental variation and change [23][24][25][26][27]. In combination with the pronounced environmental gradients in the Baltic Sea, there is hence a challenge to provide a generic description of the status of coastal predatory fish in the system without using the local perspective.…”

“…Recent studies have addressed the past status (data until 2013) of predatory fish as a functional group [21], potential causes for change of perch populations and predatory fish as a functional group [25,28], and population structures for coastal fish in the Baltic Sea [26]. This review is novel in several aspects including, for example, the most recent status assessment of predatory fish (data until 2016/2017), the first Baltic wide assessment of the population trends for pike and pikeperch, as well as a review of the causes for population change in coastal predatory fish and possible measures for restoring and supporting coastal predatory fish populations and stocks in the Baltic Sea.…”

Spatial genetic structure in a crustacean herbivore highlights the need for local considerations in Baltic Sea biodiversity management

“…Seascape genetic studies are scarce in the Baltic Sea. The studies undertaken to date focus mainly on commercially caught fish species (Östman, Olsson, Dannewitz, Palm, & Florin, 2017;Wennerström, Jansson, & Laikre, 2017), which show highly species-specific patterns. Some fish, such as perch and herring, are clearly structured geographically (Lamichhaney et al, 2012;Olsson, Mo, Florin, Aho, & Ryman, 2011;Teacher, André, Jonsson, & Merilä, 2013), as are species with distinct spawning areas such as cod and salmon (Barth et al, 2019;Berg et al, 2015;Poćwierz-Kotus et al, 2015).…”