Opportunities for agent‐based modelling in human dimensions of fisheries

Models of human dimensions of fisheries are important to understanding and predicting how fishing industries respond to changes in marine ecosystems and management institutions. Advances in computation have made it possible to construct agent‐based models (ABMs)—which explicitly describe the behaviour of individual people, firms or vessels in order to understand and predict their aggregate behaviours. ABMs are widely used for both academic and applied purposes in many settings including finance, urban planning and the military, but are not yet mainstream in fisheries science and management, despite a growing literature. ABMs are well suited to understanding emergent consequences of fisher interactions, heterogeneity and bounded rationality, especially in complex ecological, social and institutional contexts. For these reasons, we argue that ABMs of human behaviour can contribute significantly to human dimensions of fisheries in three areas: (a) understanding interactions between multiple management institutions; (b) incorporating cognitive and behavioural sciences into fisheries science and practice; and (c) understanding and projecting the social consequences of management institutions. We provide simple examples illustrating the potential for ABMs in each of these areas, using conceptual (“toy”) versions of the POSEIDON model. We argue that salient strategic advances in these areas could pave the way for increased tactical use of ABMs in fishery management settings. We review common ABM development and application challenges, with the aim of providing guidance to beginning ABM developers and users studying human dimensions of fisheries.     

Synthetic Fibers as Indicators of Municipal Sewage Sludge,Sludge Products,and Sewage Treatment Plant Effluents

Because of concerns regarding health, safety, and aesthetics, a test that identifies the presence of sewage sludge or its products (biosolids) in commercial materials such as soil conditioners and composts would be useful. This test could also trace the effluent plume from a sewage treatment plant. We have discovered that synthetic fibers serve as such an indicator. Synthetic fibers are abundant in sludge, sludge products, and sewage treatment plant effluents. The fibers evidently are introduced from clothes-washing machines and survive the sewage treatment process. Synthetic fibers were identified using polarized light microscopy, which provided a simple, rapid method for determining the presence or absence of municipal sewage sludge or its products. False positives or false negatives have not occurred with any of the materials examined so far. We also monitored synthetic fibers in surface sediments of Huntington Harbor, Long Island, NY, a harbor receiving the effluent from a trickling filter sewage treatment plant. Fibers generally decrease in size and abundance with distance from the source. In Oyster Bay Harbor, Long Island, an advanced sewage treatment plant is operated with a final microfiltration step. Synthetic fibers are less abundant in the sediments of this harbor.     

Climate-Ocean Variability and Ecosystem Response in the Northeast Pacific

The role of climatic variation in regulating marine populations and communities is not well understood. To improve our knowledge, the sign, amplitude, and frequency of climatic and biotic variations should be compared as a necessary first step. It is shown that there have been large interannual and interdecadal sea-surface temperature changes off the West Coast of North America during the past 80 years. Interannual anomalies appear and disappear rather suddenly and synchronously along the entire coastline. The frequency of warm events has increased since 1977. Although extensive, serial, biological observations are often incomplete, it is clear that climate-ocean variations have disturbed and changed our coastal ecosystems.     

Evidence for extreme climatic warmth from late cretaceous arctic vertebrates

A Late Cretaceous (92 to 86 million years ago) vertebrate assemblage from the high Canadian Arctic (Axel Heiberg Island) implies that polar climates were warm (mean annual temperature exceeding 14 degreesC) rather than near freezing. The assemblage includes large (2.4 meters long) champsosaurs, which are extinct crocodilelike reptiles. Magmatism at six large igneous provinces at this time suggests that volcanic carbon dioxide emissions helped cause the global warmth.     

Killer whale predation on sea otters linking oceanic and nearshore ecosystems

After nearly a century of recovery from overhunting, sea otter populations are in abrupt decline over large areas of western Alaska. Increased killer whale predation is the likely cause of these declines. Elevated sea urchin density and the consequent deforestation of kelp beds in the nearshore community demonstrate that the otter's keystone role has been reduced or eliminated. This chain of interactions was probably initiated by anthropogenic changes in the offshore oceanic ecosystem.     

Protactinium-231 and thorium-230 abundances and high scavenging rates in the western arctic ocean

The Canadian Basin of the Arctic Ocean, largely ice covered and isolated from deep contact with the more dynamic Eurasian Basin by the Lomonosov Ridge, has historically been considered an area of low productivity and particle flux and sluggish circulation. High-sensitivity mass-spectrometric measurements of the naturally occurring radionuclides protactinium-231 and thorium-230 in the deep Canada Basin and on the adjacent shelf indicate high particle fluxes and scavenging rates in this region. The thorium-232 data suggest that offshore advection of particulate material from the shelves contributes to scavenging of reactive materials in areas of permanent ice cover.     

There has never been a better time or a greater need for resistance management

Integrated pest management (IPM) and sustainable agriculture benefit from selective and environmentally benign crop-protection products. The performance of these products, however, is threatened by resistance. If it is to be prevented from standing in the path of progress, resistance must be managed. As agricultural practices move towards IPM and sustainable crop protection, selection pressure will be concentrated on products which are compatible with these systems. Producers, researchers, government and extension workers cannot solve these complex problems alone. The key to success is collaboration. The Insecticide Resistance Action Committee (IRAC) was set up by the crop-protection industry in 1984 to promote and co-ordinate its contribution to resistance management. Today, it is collaborating with research institutes, government organisations and extension services to combat resistance. IRAC focuses on research and communication projects which reduce selection pressure, organising workshops in ‘resistance hot spots’ and providing input to draft legislation. Selected examples of IRAC's collaborative work are described. ©1997 SCI     

Test performance study for detection of Ralstonia solanacearum and Clavibacter sepedonicus in potato tubers with TaqMan PCR

A test performance study (TPS) was organized in 2018 with ten official testing laboratories to evaluate the performance of different real-time PCR tests for the detection of Clavibacter sepedonicus and/or Ralstonia solanacearum in potato tubers. Participants were sent spiked potato extracts with low (0.8–1.2 × 10⁴ cfu mL^-1), medium (1.6–2.4 × 10⁵ cfu mL^-1) and high (1.6–2.4 × 10⁷ cfu mL^-1) bacterial loads, DNA extracts thereof and heel-end cores from symptomatic potato tubers. The four real-time PCR tests in this TPS for detection of C. sepedonicus were considered fit for purpose as principal screening methods. Two real-time PCRs in this TPS were considered fit for purpose as principal screening methods for detection of R. solanacearum. A third real-time PCR missed 23% of the DNA samples from low-level R. solanacearum spikes and is considered not fit for purpose as a principal screening method. Correct identification of spiked samples was lower when DNA extraction from the spiked samples was performed by the participating laboratories, highlighting the importance of appropriate DNA extraction protocols.     

Cleaved PARP‐1, an Apoptotic Marker,can be Detected in Ram Spermatozoa

The presence of apoptotic features in spermatozoa has been related to lower quality and functional impairment. Members of the poly‐ADP‐ribose polymerases (PARP) familyare involved in both DNA repair and apoptosis, playing important roles in spermatogenesis. Poly‐ADP‐ribose polymerase can be cleaved by caspases, and the presence of its cleavage product (cPARP) in spermatozoa has been related to chromatin remodelling during spermatogenesis and to the activation of apoptotic pathways. There are no reports on immunodetection of cPARP in ram spermatozoa; thus, we have tested a commercially available antibody for this purpose. cPARP was microscopically detected in the acrosomal ridge of some spermatozoa (indirect immunofluorescence). A preliminary study was carried out by flow cytometry (direct immunofluorescence, FITC). Ram semen was extended in TALP and incubated for 4 h with apoptosis inducers staurosporine (10 μm ) or betulinic acid (200 μm ). Both inducers and incubation caused a significant increase in cPARP spermatozoa (0 h, control: 21.4±3.3%, inducers: 44.3±1.4%; 4 h, control: 44.3±2.4%, inducers: 53.3±1.4%). In a second experiment, we compared the sperm fractions after density gradient separation (pellet and interface). The pellet yielded a slightly lower proportion of cPARP spermatozoa (28.5±1.2% vs 36.2±2.0% in the interface; p < 0.001), and a 12‐h incubation increased cPARP similarly in both fractions (p < 0.001). cPARP seems to be an early marker of apoptosis in ram semen, although its presence in untreated samples was weakly related to worse quality (pellet/interface). We suggest to study the relationship of PARP and cPARP levels with between‐male differences on sperm fertility.