Andreou, D. | Search bioRxiv

bioRxiv2022

Relationships of scale cortisol content suggests stress resilience in freshwater fish vulnerable to catch-and-release angling in recreational fisheries

The capture by angling of an individual fish is recognised as a short-term physiologically stressor. In fish populations exploited by catch and release angling (C&R), there is potential for some individual fishes to be captured on multiple occasions, but the longer term physiological consequences of this remain uncertain. Using scale cortisol content as a biomarker of chronic stress and scale samples from two fish populations exploited by C&R angling, we developed proxies of angling capture vulnerability before testing these proxies against scale cortisol content. In a riverine population of European barbel Barbus barbus, fish with the highest scale cortisol content were predicted as those sampled by angling rather than electric fishing, as angled fish had significantly smaller home ranges and diets based primarily on angling baits. In a population of common carp Cyprinus carpio in a small pond fishery, we predicted that fish with the highest scale cortisol content would be those with higher proportions of angling bait in their diet. In both species, however, the fish predicted to be most vulnerable to angling capture had the lowest levels of scale cortisol content. We suggest that this is through fish that are captured regularly being highly stress resilient (with this independent of other traits) or fish with traits that suggest high capture vulnerability being able to minimise their recapture rates through developing hook avoidance behaviours after an initial capture. Overall, these results suggest that scale cortisol content is a useful biomarker for measuring chronic stress from C&R angling. HighlightsO_LIIn catch-and-release angling (C&R), a single capture event is a short-term stressor C_LIO_LIThe effect of multiple capture events on individual fishes in C&R is unknown C_LIO_LIScale cortisol content was used as a biomarker of chronic stress C_LIO_LIFish of high vulnerability to capture had relatively low scale cortisol content C_LIO_LIFish with high exposure to C&R appear to have high stress resilience. C_LI

ecology↗

bioRxiv2022

Seascape genomics reveals limited dispersal and suggest spatially varying selection among European populations of sea lamprey (Petromyzon marinus)

Sea lamprey Petromyzon marinus is an anadromous and semelparous fish without homing behaviours. Despite being a freshwater, free-living organism for large part of their life cycle, its adulthood is spent as a parasite of marine vertebrates. In their native European range, while it is well-established that sea lampreys comprise a single nearly-panmictic population, few studies have further explored the evolutionary history of natural populations. Here, we performed the first genome-wide characterization of sea lampreys genetic diversity in their European natural range. The objectives were to investigate the connectivity among river basins and explore evolutionary processes mediating dispersal during the marine phase, with the sequencing 186 individuals from 8 locations spanning the North Eastern Atlantic coast and the North Sea with double-digest RAD-sequencing, obtaining a total of 30910 bi-allelic SNPs. Population genetic analyses reinforced the existence of a single metapopulation encompassing freshwater spawning sites within the north eastern Atlantic and the North Sea, though the prevalence of private alleles at northern latitudes suggested some limits to the species dispersal. Seascape genomics suggested a scenario where oxygen concentration and river runoffs impose spatially varying selection across their distribution range. Exploring associations with abundance of potential hosts further suggested that hake and cod could also impose selective pressures, although the nature of such putative biotic interactions was unresolved. Overall, the identification of adaptive seascapes in a panmictic anadromous species could contribute to conservation practices by providing information for restoration activities to mitigate local extinctions on freshwater sites. Sea lamprey Petromyzon marinus is an anadromous and semelparous fish without homing behaviours. Despite being a freshwater, free-living organism for large part of its life cycle, its adulthood is spent as a parasite of marine vertebrates. Here, we performed the first genome-wide characterization of sea lampreys genetic diversity in their European natural range. The objectives were to investigate the connectivity among river basins and explore evolutionary processes mediating dispersal during the marine phase. For that, we sequenced 186 individuals from 8 locations spanning the North-eastern Atlantic coast and the North Sea with double-digest RAD-sequencing, obtaining a total of 30910 bi-allelic SNPs. Population genomic analyses reinforced the existence of a single metapopulation encompassing freshwater spawning sites within the north-eastern Atlantic and the North Sea, though the prevalence of private alleles at northern latitudes suggested some limits to the species dispersal. Seascape analyses revealed candidate loci associated with the abundance of some host species and were located in a genomic region coding for variable lymphocyte receptors, an adaptive immunity tool unique to jawless vertebrates, and to MARCH proteins, a family of E3 ubiquitin ligases also involved in the regulation of immune responses. Abiotic factors (e.g., maximum phosphate, dissolved oxygen and water temperature) were significantly correlated with candidate loci associated with the myo-inositol synthesis, a pathway linked to osmoregulation, and to other genomic regions involved in organismal homeostasis. The identification of adaptive seascapes in this ancient species, especially if linked to primitive adaptive immune responses, could be relevant to understand the evolutionary pathways early in vertebrate evolution.

evolutionary biology↗

bioRxiv2020

A non-invasive eDNA tool for detecting sea lamprey larvae in river sediments: analytical validation and field testing in a low abundance ecosystem

Anthropogenic activities are increasingly threatening aquatic biodiversity, especially anadromous species. Monitoring and conservation measures are thus required to protect, maintain, and restore imperilled populations. While many species can be surveyed using traditional capture and visual census techniques, species that use riverine habitats in a less conspicuous manner, such as sea lamprey Petromyzon marinus, can be more challenging to monitor. Sea lamprey larvae (ammocoetes) can spend several years in freshwater burrowed within soft sediments, inhibiting their detection and assessment. Here we present an environmental DNA (eDNA) assay to detect ammocoetes burrowed in the sediment. We performed a battery of tests that ensured both species-specificity of the assay as well as the capacity to detect ammocoetes when abundances are low. Experiments on burrowing activity suggested that most of the DNA released into the sediment occurs during burrowing. Overall, we demonstrated this new molecular-based tool is an efficient and effective complement to traditional monitoring activities targeting larval stages of sea lampreys.

genetics↗