Applications of sensory biology in marine ecology and aquaculture

Journal homepage: http://www.int-res.com/journals/meps

The peer review process: perspectives and insights from a journal editor

Ever-increasing numbers of manuscripts, grant proposals, working group documents, position papers, etc. are being circulated – to an overburdened community of non-remunerated experts – for critical evaluation. Expert reviewers are fatigued. Their efforts, and particularly the amount of time required to prepare complete, well-considered and constructive critiques, are unrecognized by administrators. As a result, the peer review process is in danger of collapse. More and more colleagues are no longer able or willing to accept review assignments. I will discuss these, and related issues, from my perspective as Associate Editor-in-Chief of Marine Ecology Progress Series (MEPS). In 2007, MEPS, L&O, CJFAS and the ICES JMS will receive > 3000 manuscripts for evaluation. At least 2000 of these will be distributed for review, and some of them will be resubmitted and reviewed again. This will require approximately 10 000 reviews. With current rates of rejection, at least 1500 of these manuscripts will likely be resubmitted to other journals, which will solicit perhaps 3000–4000 more reviews. Some of those will be rejected, and resubmitted elsewhere. Thus, manuscripts initially submitted to only 4 marine science journals could easily require more than 15 000 reviews. And how many qualified experts are there out there anyways?! These numbers, and the level of non-remunerated time and effort that they represent, are meant to be sobering and will hopefully serve as the basis for an animated discussion. Keywords: peer review; quality control; inherent bias; reviewer fatigu

The copepod Calanus spp. (Calanidae) is repelled by polarized light

Both attraction and repulsion from linearly polarized light have been observed in zooplankton. A dichotomous choice experiment, consisting of plankton light traps deployed in natural waters at a depth of 30 m that projected either polarized or unpolarized light of the same intensity, was used to test the hypothesis that the North Atlantic copepod, Calanus spp., is linearly polarotactic. In addition, the transparency of these copepods, as they might be seen by polarization insensitive vs. sensitive visual systems, was measured. Calanus spp. exhibited negative polarotaxis with a preference ratio of 1.9:1. Their transparency decreased from 80% to 20% to 30% in the unpolarized, partially polarized, and electric (e-) vector orientation domains respectively - that is, these copepods would appear opaque and conspicuous to a polarization-sensitive viewer looking at them under conditions rich in polarized light. Since the only difference between the two plankton traps was the polarization cue, we conclude that Calanus spp. are polarization sensitive and exhibit negative polarotaxis at low light intensities (albeit well within the sensitivity range reported for copepods). We hypothesize that Calanus spp. can use polarization vision to reduce their risk of predation by polarization-sensitive predators and suggest that this be tested in future experiments

Denialism and muddying the water or organized skepticism and clarity? THAT is the question

The research being commented on here has been criticized and defended in journals. Sneddon et al. (2018) add nothing substantive. We have nothing further to add. Readers are referred to Diggles (2018) and to Browman et al. (2018) for a detailed assessment

Marine Protected Areas as a central element of ecosystem-based management: defining their location, size and number

Journal homepage: http://www.int-res.com/journals/meps

Developing the knowledge base needed to sustainably manage mesopelagic resources

Recent estimates suggest that the mesopelagic zone could contain a total fish biomass of 2-19.5 gigatonnes, roughly equivalent to 100 times the annual catch of all existing fisheries. In addition to the possibility of direct consumption of mesopelagic species, there is interest in their use for fishmeal, as a source of dietary supplements for humans, and to bio-prospect pharmaceuticals. All of this, and the demands for a global food supply that can feed an ever-growing population, has driven interest in the mesopelagic. Thus, accurate quantification of the biomass of mesopelagic resources, their nutritional and genetic composition, their links to other components of the food web, to other oceanic realms and to biological and chemical oceanographic processes and cycles, are the focus of growing research activity. This information is needed to ensure the sustainable management of these resources. In this introduction, we summarize the contributions included in this theme set and provide some “food for thought” on the state-of-the-art in research on the mesopelagic, including identifying the knowledge that must be generated to support its sustainable management (e.g. the effect that extracting significant biomass might have on the pelagic ecosystem and the flow of material and energy through it

Chemical Defense of the Eastern Newt (Notophthalmus viridescens): Variation in Efficiency against Different Consumers and in Different Habitats

Amphibian secondary metabolites are well known chemically, but their ecological functions are poorly understood—even for well-studied species. For example, the eastern newt (Notophthalmus viridescens) is a well known secretor of tetrodotoxin (TTX), with this compound hypothesized to facilitate this salamander's coexistence with a variety of aquatic consumers across the eastern United States. However, this assumption of chemical defense is primarily based on observational data with low replication against only a few predator types. Therefore, we tested the hypothesis that N. viridescens is chemically defended against co-occurring fishes, invertebrates, and amphibian generalist predators and that this defense confers high survivorship when newts are transplanted into both fish-containing and fishless habitats. We found that adult eastern newts were unpalatable to predatory fishes (Micropterus salmoides, Lepomis macrochirus) and a crayfish (Procambarus clarkii), but were readily consumed by bullfrogs (Lithobates catesbeianus). The eggs and neonate larvae were also unpalatable to fish (L. macrochirus). Bioassay-guided fractionation confirmed that deterrence is chemical and that ecologically relevant concentrations of TTX would deter feeding. Despite predatory fishes rejecting eastern newts in laboratory assays, field experiments demonstrated that tethered newts suffered high rates of predation in fish-containing ponds. We suggest that this may be due to predation by amphibians (frogs) and reptiles (turtles) that co-occur with fishes rather than from fishes directly. Fishes suppress invertebrate consumers that prey on bullfrog larvae, leading to higher bullfrog densities in fish containing ponds and thus considerable consumption of newts due to bullfrog tolerance of newt chemical defenses. Amphibian chemical defenses, and consumer responses to them, may be more complex and indirect than previously appreciated

Hypotheses of Spatial Stock Structure in Orange Roughy Hoplostethus atlanticus Inferred from Diet, Feeding, Condition, and Reproductive Activity

We evaluate hypotheses for meso-scale spatial structure in an orange roughy (Hoplostethus atlanticus) stock using samples collected during research trawl surveys off the east coast of New Zealand. Distance-based linear models and generalised additive models were used to identify the most significant biological, environmental, and temporal predictors of variability in diet, proportion of stomachs containing prey, standardised weight of prey, fish somatic weight, fish total weight, and reproductive activity. The diet was similar to that observed elsewhere, and varied with ontogeny, depth, and surface water temperature. Smaller sized and female orange roughy in warmer bottom water were most likely to contain food. Fish condition and reproductive activity were highest at distances more than 20 km from the summit of the hills. Trawl survey catches indicated greater orange roughy densities in hill strata, suggesting hill habitat was favoured. However, analyses of feeding, condition, and reproductive activity indicated hill fish were not superior, despite fish densities on hills being reduced by fishing which, in principle, should have reduced intra-specific competition for food and other resources. Hypotheses for this result include: (1) fish in relatively poor condition visit hills to feed and regain condition and then leave, or (2) commercial fishing has disturbed feeding aggregations and/or caused habitat damage, making fished hills less productive. Mature orange roughy were observed on both flat and hill habitat during periods outside of spawning, and if this spatial structure was persistent then a proportion of the total spawning stock biomass would remain unavailable to fisheries targeting hills. Orange roughy stock assessments informed only by data from hills may well be misleading

The Roles of Dimensionality, Canopies and Complexity in Ecosystem Monitoring

Canopies are common among autotrophs, increasing their access to light and thereby increasing competitive abilities. If viewed from above canopies may conceal objects beneath them creating a ‘canopy effect’. Due to complexities in collecting 3-dimensional data, most ecosystem monitoring programmes reduce dimensionality when sampling, resorting to planar views. The resultant ‘canopy effects’ may bias data interpretation, particularly following disturbances. Canopy effects are especially relevant on coral reefs where coral cover is often used to evaluate and communicate ecosystem health. We show that canopies hide benthic components including massive corals and algal turfs, and as planar views are almost ubiquitously used to monitor disturbances, the loss of vulnerable canopy-forming corals may bias findings by presenting pre-existing benthic components as an altered system. Our reliance on planar views in monitoring ecosystems, especially coral cover on reefs, needs to be reassessed if we are to better understand the ecological consequences of ever more frequent disturbances

Fishing in the Dark: A Pursuit-Diving Seabird Modifies Foraging Behaviour in Response to Nocturnal Light Levels

Visual predators tend not to hunt during periods when efficiency is compromised by low light levels. Yet common murres, a species considered a diurnal visual predator, frequently dive at night. To study foraging of murres under different light conditions, we used a combination of archival tagging methods and astronomical models to assess relationships between diving behaviour and light availability. During diurnal and crepuscular periods, murres used a wide range of the water column (2–177 m), foraging across light intensities that spanned several orders of magnitude (103–10−10 Wm−2). Through these periods, they readily dived under conditions equivalent to ambient moonlight (∼10−4 Wm−2) but rarely under conditions equivalent to starlight (∼10−8 Wm−2). At night, murres readily foraged during both moonlit and starlit periods, and diving depth and efficiency increased with nocturnal light intensity, suggesting that night diving is at least partially visually guided. Whether visually guided foraging is possible during starlit periods is less clear. Given the dense prey landscape available, random-walk simulations suggest that murres could benefit from random prey encounters. We hypothesise that murres foraging through starlit periods rely either on close-range visual or possibly nonvisual cues to acquire randomly encountered prey. This research highlights the flexibility of breeding common murres and raises questions about the strategies and mechanisms birds use to find prey under very low light conditions