The global lockdown to mitigate COVID-19 pandemic health risks has altered human interactions with nature. Here, we report immediate impacts of changes in human activities on wildlife and environmental threats during the early lockdown months of 2020, based on 877 qualitative reports and 332 quantitative assessments from different studies. Hundreds of reports of unusual species observations from around the world suggest that animals quickly responded to the reductions in human presence. However, negative effects of lockdown on conservation also emerged, as confinement resulted in some park officials being unable to perform conservation, restoration and enforcement tasks, resulting in local increases in illegal activities such as hunting. Overall, there is a complex mixture of positive and negative effects of the pandemic lockdown on nature, all of which have the potential to lead to cascading responses which in turn impact wildlife and nature conservation. While the net effect of the lockdown will need to be assessed over years as data becomes available and persistent effects emerge, immediate responses were detected across the world. Thus, initial qualitative and quantitative data arising from this serendipitous global quasi-experimental perturbation highlights the dual role that humans play in threatening and protecting species and ecosystems. Pathways to favorably tilt this delicate balance include reducing impacts and increasing conservation effectiveness.
Microchemical analyses of fish otoliths have revolutionized fisheries science. Molecules deposited within otoliths may originate from ambient water and diet, with molecular concentrations being subject to subsequent physiological alteration after exposure. Analyses of otolith microstructure and incorporation of inorganic elements have led to major advances in stock assessment and fisheries ecology. However, the use of otoliths for microchemical analyses has drawbacks. Specifically, otolith removal from live specimens requires specimen sacrifice, which may be forbidden in the case of protected species. In addition, otoliths rarely contain sufficient concentrations of organic matter to allow reconstruction of food-web relationships via multiple stable isotopes, and otolith microstructure can be difficult to interpret in some species. Here, we review alternatives to otoliths that can provide microchemical analytes for life-history studies in fishes. Our focus is to describe advantages and disadvantages to the use of each alternative structure, with particular attention paid to trace-element analysis for inorganic matrices and stable-isotope analysis for organic ones. In general, the chronological analysis of elemental and isotopic values within each structure depends on the inert nature (or lack of molecular turnover) of the tissue. Structures with high turnover rates or those that are metabolically active will not effectively record elemental or isotopic compositions over time. Here, we provide an assessment of the use of bony endoskeleton, fin spines, fin rays, scales, and eye lenses as alternatives or complements to fish otolith analysis.
In marine ecosystems, little is known about how competition with invasive fishes may affect the resource use of native predators. Throughout the western Atlantic, invasive Indo-Pacific lionfishes (Pterois spp.) are likely to compete with native mesopredators such as the graysby Cephalopholis cruentata, an ecologically similar serranid. In conjunction with a before-after-controlimpact lionfish removal experiment, this study measured whether graysby population size, diet, and condition varied in relation to cohabitant lionfish biomass. Lionfish, graysby, and prey populations were surveyed and sampled along a contiguous reef ledge in Biscayne National Park, south Florida. Mesopredator diet was measured with stable isotope (δ 13 C and δ 15 N) and gut content analyses, and isotopic niches were used to compare patterns of inter-and intraspecific resource use diversity. The isotopic niches of graysby and lionfishes overlapped by 67%, suggesting similar population-level resource use. On sites with higher lionfish biomass, graysby isotopic niche was 34% smaller and overlapped 47% less with that of lionfishes, possibly indicating both a narrower breadth of resource use and associated interspecific niche segregation. Although gut content analyses suggested that graysby may consume less fishes on high lionfish biomass sites, prey fish populations did not vary accordingly, potentially inferring interference by lionfishes on graysby foraging behavior. However, graysby condition was not related to lionfish biomass, so the 2 species ultimately did not fit the classic definition of competitors. By discussing potential influences of lionfishes on graysby resource use, our research contributes useful information to the study of how invasive lionfishes may affect native predator communities.
Patterns of stable isotopes recorded in metabolically stable, serially synthesized, structures such as eye lenses can yield robust descriptions of resource use across the life histories of individual fish. We performed stable isotope analysis of eye lenses sampled from invasive lionfishes Pterois spp. and a potentially competitive native mesopredator, the graysby Cephalopholis cruentata, to compare lifelong patterns of trophic resource use on a coral reef ledge in Biscayne National Park, Florida, USA. In both lionfishes and graysby, stable isotope values increased logarithmically with eye-lens radius, likely reflecting increases in trophic position with growth. Tissue samples toward the interior of the lens were the most isotopically similar between lionfish and graysby, suggesting interspecific resource use overlap may be strongest in smaller fish. We observed substantial variation in isotopic chronologies around the underlying logarithmic trend within individual fish, potentially driven by patterns of movement across measured environmental isotopic gradients, intraspecific variation in resource use specificity, or other ecological variables of interest. These results are the first to describe patterns of size-structured resource use across the life of individual lionfish, an important objective for researchers studying the interactions of this highly invasive species with the surrounding ecological communities. Additionally, through this example, we illustrate analytical approaches and considerations for the application of eye-lens stable isotope analysis to the study of vertebrate ecology.
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