A giant nektobenthic radiodont from the Burgess Shale and the significance of hurdiid carapace diversity

Radiodonts, stem-group euarthropods that evolved during the Cambrian explosion, were among the largest and most diversified lower palaeozoic predators. These animals were widespread geographically, occupying a variety of ecological niches, from benthic foragers to nektonic suspension feeders and apex predators. Here, we describe the largest Cambrian hurdiid radiodont known so far, Titanokorys gainesi , gen. et sp. nov., from the Burgess Shale (Marble Canyon, Kootenay National Park, British Columbia). Estimated to reach half a metre in length, this new species bears a very large ovoid-shaped central carapace with distinct short posterolateral processes and an anterior spine. Geometric morphometric analyses highlight the high diversity of carapace shapes in hurdiids and show that Titanokorys bridges a morphological gap between forms with long and short carapaces. Carapace shape, however, is prone to homoplasy and shows no consistent relationship with trophic ecology, as demonstrated by new data, including a reappraisal of the poorly known Pahvantia . Despite distinct carapaces, Titanokorys shares similar rake-like appendages for sediment-sifting with Cambroraster, a smaller but much more abundant sympatric hurdiid from the Burgess Shale . The co-occurrence of these two species on the same bedding planes highlights potential competition for benthic resources and the high diversity of large predators sustained by Cambrian communities.

Integrating human and ecological dimensions: The importance of stakeholders’ perceptions and participation on the performance of fisheries co-management in Chile

Increasing attention is paid to the interdependence between the ecological and human dimensions to improve the management of natural resources. Understanding how artisanal fishers see and use the common-pool resources in a co-management system may hold the clue to establishing effective coastal fisheries policies or strengthening existing ones. A more comprehensive planning of the system will also have a bearing on how to reduce conflicts and strengthen social networks. We surveyed artisanal fishers and decision-makers to determine their perceptions about the Management and Exploitation Areas of Benthic Resources (known as MEABR) in Chile’s Biobio region. We performed a field study from November 2018 to August 2019, applying a set of questionnaires to determine the ecological and human attributes that contribute to MEABR outcomes, and then constructed composite scores for those attributes according to a multidimensional scaling technique (“Rapfish”). We find that fishers have different perspectives: surprisingly, women highlighted that the institutional dimension was the most influential on MEABR performance, whereas men highlighted the ecological and economic outcomes. The decision-makers’ role in the MEABR system was considered adequate, but communication and socialization of regulations were irregular. Results also showed that fishers expressed dissatisfaction with illegal fishing practices (poaching), productivity, profits, and conflicts inside and outside the MEABRs. Our study allowed us to better understand how the MEABR has developed in the region. We recommend strengthening local management strategies with particular attention paid to networking among stakeholders, including gender inclusive relationships.

Fatty acid accumulation in feeding types of a natural freshwater fish population

Fatty acids are widely used to study trophic interactions in food web assemblages. Generally, it is assumed that there is a very small modification of fatty acids from one trophic step to another, making them suitable as trophic biomarkers. However, recent literature provides evidence that many fishes possess genes encoding enzymes with a role in bioconversion, thus the capability for bioconversion might be more widespread than previously assumed. Nonetheless, empirical evidence for biosynthesis occurring in natural populations remains scarce. In this study, we investigated different feeding types of perch (Perca fluviatilis) that are specialized on specific resources with different levels of highly unsaturated fatty acids (HUFAs), and analyzed the change between HUFA proportions in perch muscle tissue compared to their resources. Perch showed matching levels to their resources for EPA, but ARA and especially DHA were accumulated. Compound-specific stable isotope analyses helped us to identify the origin of HUFA carbon. Our results suggest that perch obtain a substantial amount of DHA via bioconversion when feeding on DHA-poor benthic resources. Thus, our data indicate the capability of bioconversion of HUFAs in a natural freshwater fish population.

Marine stocking in Chile: a review of past progress and future opportunities for enhancing marine artisanal fisheries

Chile has a long history of restocking, stock enhancement, and translocation to support artisanal or small-scale fisheries; however, these programs have been scarcely discussed in the scientific literature. Here, we present a review of previous initiatives and discuss specific areas for future progress. We identified 204 releases across 117 different areas, involving 7 taxonomic groups and 22 species (20 marine and 2 freshwater). Marine stocking mainly occurred within the context of the spatial framework through which artisanal fisheries are managed [Management and Exploitation Areas for Benthic Resources (MEABR)], and over 60% involved translocation of wild individuals rather than release of hatchery-reared seed. While “stock enhancement” was the primary intention for most releases, it is unclear whether depleted spawning biomass or other recruitment limitations were the primary motivation, and few projects reported more than one stocking event. The echinoid Loxechinus albus and the gastropod Concholepas concholepas were the main target species. Only 6% of projects examined reported positive results that could be linked to releases, and none reported the use of tagging or analysis of costs or benefits. There are several areas for targeted development that should improve the social and economic outcomes from marine stocking activities. This synthesis provides a snapshot of marine stocking in Chile to date and highlights opportunities that are relevant to both Chile and other nations with substantial small-scale fisheries.

Co-Management of Small-Scale Fisheries in Chile From a Network Governance Perspective

We examine decision-making, shared authority, and pluralism as key characteristics for the effective co-management of natural resources. Drawing on the concept of network governance, we complement this approach by studying localized practices of governance that support existing and compensate for missing aspects in the regulation. The regime of territorial use rights for fisheries (TURF) in Chile is a recognized example of large-scale co-management that has given rise to local organizations that manage and exploit benthic resources. Based on multi-sited qualitative fieldwork across five regions, we analyze practices with respect to two governance objects: the deterrence of illegal fishing and the periodic assessment of the fisheries’ biology fields. Our analysis shows that local fisher organizations have institutionalized informal practices of surveillance and monitoring to fill in the gaps of existing regulations. Although fisher organizations and consultants—the so-called management and exploitation areas for benthic resources (AMERB)—have managed to operate the TURF regime, they depend on the government to enforce regulations and receive public subsidies to cover the costs of delegated governance tasks. We suggest that governance effectiveness could benefit from delegating additional authority to the local level. This would enhance the supervision of productive areas and better adaptation of national co-management regulations to the specific geographical context.

Sustainability of the Artisanal Fishery in Northern Chile: A Case Study of Caleta Pisagua

The Humboldt Current, one of the most productive waters in the world, flows along the Chilean coast with high primary production level. However, living marine resources in these waters are declining due to overexploitation and other anthropogenic and environmental factors. It has been reported that deploying artificial reefs in coastal waters can improve the production of benthic resources. To ensure the sustainability of coastal fisheries in northern Chile this study aims to investigate fishermen’s perceptions on deploying artificial reefs and propose future management measures using Caleta Pisagua as a case study. Interviews of artisanal fishermen regarding four aspects: fishermen profile, fishing activity, resources, and artificial reefs were conducted. Results showed that most fishermen favored the implementation of artificial reefs within the Areas of Management and Exploitation of Benthic Resources (AMERBs). In addition, deploying artificial reefs appears to be socio-economically necessary for the artisanal fishermen whose livelihood is being affected by the overexploitation of coastal fish and because hard substrates essential for benthic resources are in short supply within this administration area. It is recommended that criteria for the deployment of artificial reefs as well as specific management plans for main and secondary species should be developed.

The freshwater mysid Mysis diluviana (Audzijonyte & Väinölä, 2005) (Mysida: Mysidae) consumes detritus in the presence of Daphnia (Cladocera: Daphniidae)

Freshwater mysids of the Mysis relicta group are omnivorous macroinvertebrates that form an important link between fishes and lower trophic levels in many north temperate to Arctic lakes, where they exhibit diel vertical migration (DVM) to exploit subsurface food-rich layers at night. Benthic food resources have been assumed to be less important for mysid diets than pelagic zooplankton. Studies have nevertheless indicated that mysids consume benthic sedimented detritus, calling this assumption into question. We conducted a food-choice experiment to evaluate the feeding preferences of Mysis diluviana (Audzijonyte & Väinölä, 2005) by presenting field-caught specimens in individual foraging arenas with multiple choices of food. Experimental food treatments included a preferred pelagic prey (Daphnia), a presumed less desirable benthic resource (detritus), and a combination of both. We hypothesized that M. diluviana 1) prefers Daphnia over detritus and consumes only Daphnia in combination treatments, and 2) would not consume detritus except when detritus was the only food source available. Contrary to our hypothesis, M. diluviana readily consumed detritus in the presence of Daphnia. Mysis diluviana unexpectedly consumed more individuals of Daphnia in the presence rather than in the absence of detritus. Our results demonstrate that mysids take advantage of benthic food resources even in the presence of a presumably preferred zooplankton prey, calling to question the long-held assumption that benthic resources are unimportant when considering the trophic role of freshwater mysids of the M. relicta group.

Abundancia y estructura poblacional de dos recursos pesqueros bentónicos fuera y dentro del área de una concesión marítima portuaria en Caldera, Región de Atacama, Chile

This study compares density and size structure of kelp Lessonia berteroana and sea urchins Loxechinus albus inside and outside a port concession area in Caldera. Greater abundance and larger adult individuals in populations of both benthic resources in this zone preliminarily indicates that this might be replicating a marine protected area. In the future, this port concession could contribute to the conservation of benthic resources as a reference site, without access to fisheries, useful for validating or implementing measures and actions in management plans or other instruments to support conservation.