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Sustainable fishery practices require accurate predictions of fish recruitment—the abundance of a new year class entering a fishery. A key driver of recruitment is the impact predator-prey dynamics experienced during early life stages has on their survival at later stages, as in the Match-Mismatch Hypothesis (MMH). MMH states that predator survival depends on the match (or mismatch) between the timing of predator feeding and that of prey availability. This study aims to understand how predator-prey spatio-temporal overlap explains the variation in a pelagic fish population. We explore the predator-prey overlap between each pair of three trophic levels in the North Sea (NS) from 1982–2017: herring (Clupea harengus) larvae, zooplankton (Temora longicornis, Oithona sp.,Pseudocalanus spp., and Acartia spp.), and a phytoplankton index. We found that MMH explained 23% of recruitment (1-year-old) of NS autumn-spawning (NSAS) herring, performed similarly (21–26%) when using different trophic levels, and that there was a spatial pattern in both the overlap and the negative relationship between the overlap and recruitment, similar to the variation of habitat use of NS herring. Our results characterize how the MMH, including spatial variability, plays in controlling herring recruitment, while also considering unexplained variation for future study.

The south shore of Oʻahu, Hawaiʻi is one of the most visited coastal tourism areas in the United States with some of the highest instances of recreational waterborne disease. A population of the pathogenic bacterium Vibrio vulnificus lives in the estuarine Ala Wai Canal in Honolulu which surrounds the heavily populated tourism center of Waikīkī. We developed a statistical model to predict V. vulnificus dynamics in this system using environmental measurements from moored oceanographic and atmospheric sensors in real time. During a year-long investigation, we analyzed water from 9 sampling events at 3 depths and 8 sites along the canal (n = 213) for 36 biogeochemical variables and V. vulnificus concentration using quantitative polymerase chain reaction (qPCR) of the hemolysin A gene (vvhA). The best multiple linear regression model of V. vulnificus concentration, explaining 80% of variation, included only six predictors: 5-day average rainfall preceding water sampling, daily maximum air temperature, water temperature, nitrate plus nitrite, and two metrics of humic dissolved organic matter (DOM). We show how real-time predictions of V. vulnificus concentration can be made using these models applied to the time series of water quality measurements from the Pacific Islands Ocean Observing System (PacIOOS) as well as the PacIOOS plume model based on the Waikīkī Regional Ocean Modeling System (ROMS) products. These applications highlight the importance of including DOM variables in predictive modeling of V. vulnificus and the influence of rain events in elevating nearshore concentrations of V. vulnificus. Long-term climate model projections of locally downscaled monthly rainfall and air temperature were used to predict an overall increase in V. vulnificus concentration of approximately 2- to 3-fold by 2100. Improving these predictive models of microbial populations is critical for management of waterborne pathogen risk exposure, particularly in the wake of a changing global climate.

Environmental temperature directly controls the rate at which ectotherms grow and develop. The growing degree-day metric (GDD, °C·day) scales time by temperature to create a thermal time scale relevant to ectothermic organisms. Here we assess the ability of GDD to model size-at-age and duration-to-moult in 15 datasets (9 size-at-age, 6 duration-to-moult) comprising 7 species of lobsters and crabs. We applied generalized linear models to assess the ability of GDD vs. “calendar” time to explain growth and development observations within and across trials. Best-fit models included GDD with fewer parameters in 6 of 9 size-at-age and 5 of 6 duration-to-moult datasets and a better fit to the data in 6 of 9 size-at-age datasets. Our results show that the individual growth of lobster and crab species can be modelled using thermal time models. Such models can be used to identify thermal tolerance limits, predict growth under varying temperature conditions and disentangle temperature effects from those of other factors affecting individual growth and development, resulting in improved growth models for field conditions including fisheries management.

A key process affecting variation in the recruitment of fish into fisheries is the spatio-temporal overlap between prey and predator (match-mismatch hypothesis, MMH). The Northeast Arctic cod Gadus morhua and its dominant prey, the copepod Calanus finmarchicus, have long been studied in the Norwegian-Barents Sea system. However, the mechanistic explanation of how cod survival is affected by MMH dynamics remains unclear. Most MMH studies have focused on either the time synchrony or the spatial overlap between trophic levels. Here, we used G. morhua larvae and C. finmarchicus data collected in the Norwegian-Barents Sea via ichthyoplankton surveys from 1959-1992 to assess the effect of the predator-prey relationship on predator recruitment to the fisheries at age 3 (as a measure of survival) and to develop a metric of predator-prey overlap using spatio-temporal statistical models. We then compared the interannual variability of the predator-prey overlap with the predator’s abundance at recruitment to assess how MMH dynamics explain the survival of cod during its early life stages. We found that the amount of overlap between cod larvae (length: 11-15 mm) and their prey explained 29% of cod recruitment variability. Positive correlations between predator-prey overlap and subsequent recruitment were also found for predators of 6-10 and 16-20 mm, but not for 21+ mm. This improved predator-prey overlap metric is thus (1) useful to better understand how predator-prey dynamics at early life stages of fish impact the survival of later stages; and (2) a valuable tool for assessing the state of an ecosystem.

Enhancement of phytoplankton biomass near island and atoll reef ecosystems—termed the Island Mass Effect (IME)—is an ecologically important phenomenon driving marine ecosystem trophic structure and fisheries in the midst of oligotrophic tropical oceans. This study investigated the occurrence of IME at Rangiroa Atoll in the French Polynesian Tuamotu archipelago, and the physical mechanisms driving IME, through the analysis of satellite and in situ data. Comparison of chlorophyll-a concentration near Rangiroa Atoll with chlorophyll-a concentration in open ocean water 50 km offshore, over a 16-year period, showed phytoplankton enhancement as high as 130% nearshore, over 75.7% of the study period. Our statistical model examining physical drivers showed the magnitude of IME to be significantly enhanced by higher sea surface temperature (SST) and lower photosynthetically active radiation (PAR). Further, in situ measurements of water flowing through Tiputa Channel revealed outflowing lagoon water to be warmer, lower in salinity, and higher in particulate load compared to ocean water. We suggest that water inside Rangiroa’s lagoon is enriched in nutrients and organic material by biological processes and advected as a result of tidal and wave forcing to coastal ocean waters, where it fuels primary production. We suggest that a combination of oceanographic and biological mechanisms is at play driving frequency and magnitude of IME at Rangiroa Atoll. Understanding the underlying processes driving IME at Rangiroa is essential for understanding future changes caused by a warming climate and changing environmental conditions for the marine ecosystem.

The deep sea (>500 m ocean depth) is the largest global habitat, characterized by cool temperatures, low ambient light, and food-poor conditions relative to shallower waters. Deep-sea teleosts generally grow more slowly than those inhabiting shallow water. However, this is a generalization, and even amongst deep-sea teleosts, there is a broad continuum of growth rates. The importance of potential drivers of growth rate variability amongst deep-sea species, such as temperature, food availability, oxygen concentration, metabolic rate, and phylogeny, have yet to be fully evaluated. We present a meta-analysis in which age and size data were collected for 53 species of teleosts whose collective depth ranges span from surface waters to 4000 m. We calculated growth metrics using both calendar and thermal age, and compared them with environmental, ecological, and phylogenetic variables. Temperature alone explained up to 30% of variation in the von Bertalanffy growth coefficient (K, yr-1), and 21% of the variation in the average annual increase in mass (AIM, %), a metric of growth prior to maturity. After correcting for temperature effects, depth was still a significant driver of growth, explaining up to 20 and 10% of the remaining variation in K and AIM, respectively. Oxygen concentration also explained ~11% of remaining variation in AIM following temperature correction. Relatively minor amounts of variation may be explained by food availability, phylogeny, and the locomotory mode of the teleosts. We also found strong correlation between growth and metabolic rate, which may be an underlying driver also related to temperature, depth, and other factors, or the 2 parameters may simply covary as a result of being linked by evolutionary pressures. Evaluating the influence of ecological and/or environmental drivers of growth is a vital step in understanding both the evolution of life history parameters across the depth continuum as well as their implications for species’ resilience to increasing anthropogenic stressors.

Marine species may respond and adapt to climate change through shifting spatial distributions, but options may be limited by the occupancy of essential habitats which are anchored in space. Limited knowledge of when spatial constraints are most likely to occur in marine fish life cycles has impeded the development of realistic distribution forecasts. In this study, we develop and implement analytical techniques to identify spatial constraints, defined by both the consistency through which a particular geographic area is used year after year, and by the extent of such area with respect to the entire population range. This approach is applied to simulated data and to ten case-studies including six groundfish species from three subarctic marine systems. Our analyses illustrate that the early phase of the species’ life cycle is more spatially constrained than older life stages. We detected significant species-specific variability in both the degree to which species are anchored in space throughout their life cycle, and the ontogenetic changes in the geographic association. There is an indication that this variability can be explained by the species life history strategy, highlighting the need to extend similar analyses to other species and regions. The presence of ontogenetic spatial constraints, particularly during early life stages, indicates restrictions exist to changes in spatial distribution and questions the assertion that global warming will uniformly result in an increase in abundance and harvest at higher latitudes and decreases at lower latitudes. Our study develops ecological and analytical insights that are critical for accurate projections of species distributions under different climate change scenarios.

Co-existence of sympatric populations of a fish species is a common phenomenon. In the fjords of southern Norway, 2 ecotypes of Atlantic cod Gadus morhua co-exist during their juvenile life stage. Cod of the North Sea ecotype are on average 2 cm larger than the fjord ecotype at the end of their first growing season in October, suggesting either differences in spawning time or differences in growth during the larval and early juvenile phase. We analysed 24352 daily otolith increments from 145 cod sampled in September 2000, 2003, 2008 and 2015 at 2 locations to estimate individual hatching times and daily growth rates. There was no significant difference in hatching time between ecotypes, locations or years. Population-specific models of the effect of year, temperature and fish length on growth rates showed that the North Sea ecotype grew significantly faster than the fjord ecotype, but growth rate differences were small until the juveniles reached ~40 mm and disappeared again in juveniles larger than 110 mm. The size range (40-110 mm) corresponds to the period following settling. This study documents how vital rates (e.g. growth rates) may change rapidly at ontogenetic transition points, leading to different phenotypic trajectories in co-existing ecotypes. It also highlights the importance of settlement as a key life-history transition that may amplify small existing differences in growth rates through positive feedback of size on competitive ability and eventually recruitment.

Seamounts are ubiquitous global features often characterized by biological hotspots of diversity, biomass, and abundance, though the mechanisms responsible are poorly understood. One controversial explanation suggests seamount-induced chlorophyll enhancements (SICE) subsidize seamount ecosystems. Using a decade of satellite chlorophyll data, we report substantial long-term chlorophyll enhancements around 17% of Pacific seamounts and 45% of shallow (

Pelagic animals that form deep sea scattering layers (DSLs) represent an important link in the food web between zooplankton and top predators. While estimating the composition, density and location of the DSL is important to understand mesopelagic ecosystem dynamics and to predict top predators’ distribution, DSL composition and density are often estimated from trawls which may be biased in terms of extrusion, avoidance, and gear-associated biases. Instead, location and biomass of DSLs can be estimated from active acoustic techniques, though estimates are often in aggregate without regard to size or taxon specific information. For the first time in the open ocean, we used a DIDSON sonar to characterize the fauna in DSLs. Estimates of the numerical density and length of animals at different depths and locations along the Kona coast of the Island of Hawaii were determined. Data were collected below and inside the DSLs with the sonar mounted on a profiler. A total of 7068 animals were counted and sized. We estimated numerical densities ranging from 1 to 7 animals/m3 and individuals as long as 3 m were detected. These numerical densities were orders of magnitude higher than those estimated from trawls and average sizes of animals were much larger as well. A mixed model was used to characterize numerical density and length of animals as a function of deep sea layer sampled, location, time of day, and day of the year. Numerical density and length of animals varied by month, with numerical density also a function of depth. The DIDSON proved to be a good tool for open-ocean/deep-sea estimation of the numerical density and size of marine animals, especially larger ones. Further work is needed to understand how this methodology relates to estimates of volume backscatters obtained with standard echosounding techniques, density measures obtained with other sampling methodologies, and to precisely evaluate sampling biases.

The Clarion-Clipperton Zone (CCZ) is one of the richest manganese nodule provinces in the world and has recently become a focus area for manganese nodule mining interests. However, this vast area remains poorly studied and highly undersampled. In this study, the abyssal bait-attending fauna is documented for the first time using a series of baited camera deployments in various locations across the CCZ. A bait-attending community intermediate between those typical of the California margin and Hawaii was found in the larger CCZ area, generally dominated by rattail fishes, dendrobranchiate shrimp, and zoarcid and ophidiid fishes. Additionally, the western and eastern ends of the CCZ had different communities, with the western region characterized by decreased dominance of rattails and small shrimps and increased dominance of ophidiids (especially Bassozetus sp. and Barathrites iris ) and large shrimps. This trend may be related to increasing distance from the continental margin. We also test the hypothesis that bait-attending communities change across the CCZ in response to key environmental predictors, especially topography and nodule cover. Our analyses showed that higher nodule cover and elevated topography, as quantified using the benthic positioning index (BPI), increase bait-attending community diversity. Elevated topography generally had higher relative abundances, but taxa also showed differing responses to the BPI metric and bottom temperature, causing significant community compositional change over varying topography and temperatures. Larger individuals of the dominant scavenger in the CCZ, Coryphaenoides spp., were correlated with areas of higher nodule cover and with abyssal hills, suggesting these areas may be preferred habitat. Our results suggest that nodule cover is important to all levels of the benthic ecosystem and that nodule mining could have negative impacts on even the top-level predators and scavengers in the CCZ. Additionally, there is continuous change in diversity, dominance, and relative abundance across the CCZ and across gradients in bathymetric and oceanographic variables. This work increased the understanding of the biogeography of the demersal scavengers and top predators as well as the key environmental drivers of their distributions across the CCZ in order to better predict and manage the impacts of nodule mining.

The Hawaiian mesopelagic boundary community is a slope-associated assemblage of micronekton that undergoes diel migrations along the slopes of the islands, residing at greater depths during the day and moving upslope to forage in shallower water at night. The timing of these migrations may be influenced by environmental factors such as moon phase or ambient light. To investigate the movements of this community, we examined echo intensity data from acoustic Doppler current profilers (ADCPs) deployed at shallow and deep sites on the southern slope of Oahu, Hawaii. Diel changes in echo intensity (and therefore in estimated backscatter) were observed and determined to be caused, at least in part, by the horizontal migration of the mesopelagic boundary community. Generalized additive modeling (GAM) was used to assess the impact of environmental factors on the migration timing. Sunset time and lunar illumination were found to be significant factors. Movement speeds of the mesopelagic boundary community were estimated at 1.25–1.99 km h-1 (35–55 cm s-1). The location at which the migrations were observed is the future site of a seawater air conditioning system, which will cause artificial upwelling at our shallow observation site and may cause animal entrainment at the seawater intake near our deep water observation site. This study is the first to observe the diel migration of the mesopelagic boundary community on southern Oahu in both deep and shallow parts of the habitat, and it is also the first to examine migration trends over long time scales, which allows a better assessment of the effects of seasons and lunar illumination on micronekton migrations. Understanding the driving mechanisms of mesopelagic boundary community behavior will increase our ability to assess and manage coastal ecosystems in the face of increasing anthropogenic impacts.

For living things, time proceeds relative to body temperature. In this contribution, I describe the biochemical underpinnings of this “biological time” and formalize the Biological Theory of Relativity (BTR). Paralleling Einstein’s Special Theory of Relativity, the BTR describes how time progresses across temporal frames of reference, contrasting temperature-scaled biological time with our more familiar (and constant) “calendar” time measures. By characterizing the relationship between these two time frames, the BTR allows us to position observed biological variability on a relevant time-scale. In so doing, we are better able to explain observed variation (both temperature-dependent and -independent), make predictions about the timing of biological phenomena, and even manipulate the biological world around us. The BTR presents a theoretical framework to direct future work regarding an entire landscape of fundamental biological questions across space, time and species.

The importance of survival and growth variations early in life for population dynamics depends on the degrees of compensatory density dependence and size dependence in survival at later life stages. Quantifying density- and size-dependent mortality at different juvenile stages is therefore important to understand and potentially predict the recruitment to the population. We applied a statistical state-space modelling approach to analyse time series of abundance and mean body size of larval and juvenile fish. The focus was to identify the importance of abundance and body size for growth and survival through successive larval and juvenile age intervals, and to quantify how the dynamics propagate through the early life to influence recruitment. We thus identified both relevant ages and mechanisms (i.e. density dependence and size dependence in survival and growth) linking recruitment variability to early life dynamics. The analysis was conducted on six economically and ecologically important fish populations from cold temperate and sub-arctic marine ecosystems. Our results underscore the importance of size for survival early in life. The comparative analysis suggests that size-dependent mortality and density-dependent growth frequently occur at a transition from pelagic to demersal habitats, which may be linked to competition for suitable habitat. The generality of this hypothesis warrants testing in future research.

Beaked and sperm whales are top predators living in the waters off the Kona coast of Hawai'i. Temporal and spatial analyses of the foraging activity of these two species were studied with passive acoustics techniques. Three passive acoustics recorders moored to the ocean floor were used to monitor the foraging activity of these whales in three locations along the Kona coast of the island of Hawaii. Data were analyzed using automatic detector/classification systems: M3R (Marine Mammal Monitoring on Navy Ranges), and custom-designed Matlab programs. The temporal variation in foraging activity was species-specific: beaked whales foraged more at night in the north, and more during the day-time off Kailua-Kona. No day-time/night-time preference was found in the southern end of the sampling range. Sperm whales foraged mainly at night in the north, but no day-time/night-time preference was observed off Kailua-Kona and in the south. A Generalized Linear Model was then applied to assess whether location and chlorophyll concentration affected the foraging activity of each species. Chlorophyll concentration and location influenced the foraging activity of both these species of deep-diving odontocetes.

Understanding the distribution of animals is of paramount importance for management and conservation, especially for species that are impacted by anthropogenic threats. In the case of marine mammals there has been a growing concern about the impact of human-made noise, in particular for beaked whales and other deep diving odontocetes. Foraging (measured via echolocation clicks at depth) was studied for Cuvier’s beaked whale ( Ziphius cavirostris ), sperm whale ( Physeter macrocephalus ), long-finned pilot whales ( Globicephala melas ) and Risso’s dolphin ( Grampus griseus ) using three passive acoustics recorders moored to the bottom of the ocean in a canyon area in the Ligurian Sea between July and December 2011. A Generalized Linear Model was used to test whether foraging was influenced by location and day of the year, including the possibility of interactions between predictors. Contrary to previous studies conducted by visual surveys in this area, all species were detected at all locations, suggesting habitat overlapping. However, significant differences were found in the occurrence of each species at different locations. Beaked and sperm whales foraged significantly more in the northern and western locations, while long-finned pilot whales and Risso’s dolphins hunted more in the northern and eastern location.

Phytoplankton production drives marine ecosystem trophic-structure and global fisheries yields. Phytoplankton biomass is particularly influential near coral reef islands and atolls that span the oligotrophic tropical oceans. The paradoxical enhancement in phytoplankton near an island-reef ecosystem—Island Mass Effect (IME)—was first documented 60 years ago, yet much remains unknown about the prevalence and drivers of this ecologically important phenomenon. Here we provide the first basin-scale investigation of IME. We show that IME is a near-ubiquitous feature among a majority (91%) of coral reef ecosystems surveyed, creating near-island ‘hotspots' of phytoplankton biomass throughout the upper water column. Variations in IME strength are governed by geomorphic type (atoll vs island), bathymetric slope, reef area and local human impacts (for example, human-derived nutrient input). These ocean oases increase nearshore phytoplankton biomass by up to 86% over oceanic conditions, providing basal energetic resources to higher trophic levels that support subsistence-based human populations., The Island Mass Effect (IME), where island proximity enhances phytoplankton biomass, remains a poorly understood phenomenon. Here, the authors show the IME is a common feature among Pacific reefs, driving increased production that creates biological hotspots in otherwise barren ocean basins.

Characterizing the trophic roles of deep-diving odontocete species and how they vary in space and time is challenged by our ability to observe foraging behavior. Though sampling methods are limited, foraging activity of deep-diving odontocetes can be monitored by recording their biosonar emissions. Daily occurrence of echolocation clicks was monitored acoustically for five months (July–December 2011) in the Ligurian Sea (Mediterranean Sea) using five passive acoustic recorders. Detected odontocetes included Cuvier's beaked whales ( Zipuhius cavirostris ), sperm whales ( Physeter macrocephalus ), Risso's dolphins ( Grampus griseus ), and long-finned pilot whales ( Globicephala melas ). The results indicated that the foraging strategies varied significantly over time, with sperm whales switching to nocturnal foraging in late September whereas Risso's dolphins and pilot whales foraged mainly at night throughout the sampling period. In the study area, winter nights are about five hours longer than summer nights and an analysis showed that pilot whales and Risso's dolphins adjusted their foraging activity with the length of the night, foraging longer during the longer winter nights. This is the first study to show that marine mammals exhibit diurnal foraging patterns closely correlated to sunrise and sunset.

We use a novel individual-based model (IBM) to simulate larval dispersal around the island of Moloka‘i in the Hawaiian Archipelago. Our model uses ocean current output from the Massachusetts Institute of Technology general circulation model (MITgcm) as well as biological data on four invertebrate and seven fish species of management relevance to produce connectivity maps among sites around the island of Moloka‘i. These 11 species span the range of life history characteristics of Hawaiian coral reef species and show different spatial and temporal patterns of connectivity as a result. As expected, the longer the pelagic larval duration (PLD), the greater the proportion of larvae that disperse longer distances, but regardless of PLD (3–270 d) most successful dispersal occurs either over short distances within an island (

Timing of reproduction greatly influences offspring success and resulting population production. Explaining and predicting species' dynamics necessitates disentangling the intrinsic (genotypic) and extrinsic (climatic) factors controlling reproductive timing. Here we explore temporal and spatial changes in spawning time for 21 populations of Atlantic cod (Gadus morhua) across the species' range (40° to 80° N). We estimate spawning time using a physiologically relevant metric that includes information on fish thermal history (degree-days, DD). First, we estimate spawning DD among years (within populations) to show how recent changes in spawning time can be explained by local changes in temperature. Second, we employ spawning DD to identify temperature-independent trends in spawning time among populations that are consistent with parallel adaptive evolution and the evolutionary history of the species. Finally, we use our results to estimate spawning time under future climate regimes, and discuss the implica...

Brander, K., Neuheimer, A., Andersen, K. H., and Hartvig, M. 2013. Overconfidence in model projections. – ICES Journal of Marine Science, 70: 1065–1068. There is considerable public and political interest in the state of marine ecosystems and fisheries, but the reliability of some recent projections has been called into question. New information about declining fish stocks, loss of biodiversity, climate impacts, and management failure is frequently reported in the major news media, based on publications in prominent scientific journals. Public and political awareness of the generally negative changes taking place in marine ecosystems is welcome, especially if it results in effective remedial action, but the scientific basis for such action must be reliable and uncertainties arising from models and data shortcomings must be presented fully and transparently. Scientific journals play an important role and should require more detailed analysis and presentation of uncertainties.

Explaining variability in offspring vs. adult size among groups is a necessary step to determine the evolutionary and environmental constraints shaping variability in life history strategies. This is of particular interest for life in the ocean where a diversity of offspring development strategies is observed along with variability in physical and biological forcing factors in space and time. We compiled adult and offspring size for 407 pelagic marine species covering more than 17 orders of magnitude in body mass including Cephalopoda, Cnidaria, Crustaceans, Ctenophora, Elasmobranchii, Mammalia, Sagittoidea, and Teleost. We find marine life following one of two distinct strategies, with offspring size being either proportional to adult size (e.g., Crustaceans, Elasmobranchii, and Mammalia) or invariant with adult size (e.g., Cephalopoda, Cnidaria, Sagittoidea, Teleosts, and possibly Ctenophora). We discuss where these two strategies occur and how these patterns (along with the relative size of the offspring) may be shaped by physical and biological constraints in the organism's environment. This adaptive environment along with the evolutionary history of the different groups shape observed life history strategies and possible group-specific responses to changing environmental conditions (e.g., production and distribution).

The size of an individual organism is a key trait to characterize its physiology and feeding ecology. Size-based scaling laws may have a limited size range of validity or undergo a transition from one scaling exponent to another at some characteristic size. We collate and review data on size-based scaling laws for resource acquisition, mobility, sensory range, and progeny size for all pelagic marine life, from bacteria to whales. Further, we review and develop simple theoretical arguments for observed scaling laws and the characteristic sizes of a change or breakdown of power laws. We divide life in the ocean into seven major realms based on trophic strategy, physiology, and life history strategy. Such a categorization represents a move away from a taxonomically oriented description toward a trait-based description of life in the oceans. Finally, we discuss life forms that transgress the simple size-based rules and identify unanswered questions. Fil: Andersen, K. H.. Centre for Ocean Life; Dinamarca. Technical University of Denmark; Dinamarca Fil: Berger, Tobías Miguel. Centre for Ocean Life; Dinamarca. Universidad de Copenhagen; Dinamarca Fil: Gonçalves, Rodrigo Javier. Centre for Ocean Life; Dinamarca. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Technical University of Denmark; Dinamarca. Fundación Playa Unión. Estación de Fotobiología Playa Unión; Argentina Fil: Hartvig, M.. Technical University of Denmark; Dinamarca. Universidad de Copenhagen; Dinamarca. Universität Göttingen; Alemania Fil: Heuschele, J.. Technical University of Denmark; Dinamarca. Centre for Ocean Life; Dinamarca Fil: Hylander, S.. Technical University of Denmark; Dinamarca. Linnaeus University; Suiza Fil: Jacobsen, N. S.. Centre for Ocean Life; Dinamarca. Technical University of Denmark; Dinamarca Fil: Lindemann, C.. Technical University of Denmark; Dinamarca Fil: Martens, E. A.. Centre for Ocean Life; Dinamarca. Technical University of Denmark; Dinamarca. Universidad de Copenhagen; Dinamarca Fil: Neuheimer, A. B.. Technical University of Denmark; Dinamarca. Universidad de Copenhagen; Dinamarca. University of Hawaii at Manoa; Estados Unidos Fil: Olsson, K.. Technical University of Denmark; Dinamarca. Universidad de Copenhagen; Dinamarca Fil: Palacz, A.. Technical University of Denmark; Dinamarca Fil: Prowe, A. E. F.. Centre for Ocean Life; Dinamarca. Technical University of Denmark; Dinamarca. Geomar-Helmholtz Centre for Ocean Research Kiel; Alemania Fil: Sainmont, J.. Technical University of Denmark; Dinamarca. Centre for Ocean Life; Dinamarca Fil: Traving, S. J.. Centre for Ocean Life; Dinamarca. Universidad de Copenhagen; Dinamarca Fil: Visser, A. W.. Centre for Ocean Life; Dinamarca. Technical University of Denmark; Dinamarca Fil: Wadhwa, N.. Centre for Ocean Life; Dinamarca. Technical University of Denmark; Dinamarca Fil: Kiørboe, T.. Centre for Ocean Life; Dinamarca. Technical University of Denmark; Dinamarca

Coral reefs worldwide are affected by excessive sediment and nutrient delivery from adjacent watersheds. Land cover and land use changes contribute to reef ecosystem degradation, which in turn,diminish many ecosystem services, including coastal protection, recreation, and food provisioning. The objectives of this work were to understand the role of coastal oceanic and biophysical processes in mediating the effects of sedimentation in shallow reef environments, and to assess the efficacy of land-based sediment remediation in the coastal areas near Maunalei reef, Lāna’i Island, Hawai’i. To the best of our knowledge, this was the first study of sediment dynamics on an east-facing (i.e., facing the trade winds) reef in the Hawaiian Islands. We developed ridge-to-reef monitoring systems at two paired stream bed-to-reef sites, where one of the reef sites was adjacent to a community stream sediment remediation project. We found that the two reef sites were characterized by different processes that affected the sediment removal rates; the two sites were also exposed to different amounts of sediment runoff. The community stream sediment remediation project appeared to keep at least 77 tonnes of sediment off the reef flat in one wet season. We found that resuspension of sediments on this reef was similar to that on north-facing and south-facing reefs that also are exposed to the trade winds. We posit that sites with slower sediment removal rates due to slower current velocities or high resuspension rates will require more-robust sediment capture systems on land to reduce sediment input rates and maximize potential for reef health recovery. This suggests that interventions such as local sediment remediation and watershed restoration may mitigate sediment delivery to coral reefs, but these interventions are more likely to be effective if they account for how adjacent coastal oceanographic processes distribute, accumulate, or advect sediment away from reefs. Our results on the effectiveness of gabion dam sediment capture may help guide scalable solutions for erosion control on islands.

Small temperature increases will benefit the growth of many cold-blooded animals, but laboratory studies indicate that warming can eventually exceed physiological limits, resulting in reduced growth. Evidence shows that this may have already happened for a fish species—the banded morwong—in the Tasman Sea. Climate change can affect organisms both directly, by affecting their physiology, growth, and behaviour1, and indirectly, for example through effects on ecosystem structure and function1,2. For ectotherms, or ‘cold-blooded’ animals, warming will directly affect their metabolism, with growth rates in temperate species predicted to increase initially as temperatures rise, but then decline as individuals struggle to maintain cardiac function and respiration in the face of increased metabolic demands3,4. We provide evidence consistent with this prediction for a marine fish (Cheilodactylus spectabilis) in the Tasman Sea; one of the most rapidly warming regions of the Southern Hemisphere ocean5. We estimated changes in the species’ growth rate over a 90-year period using otoliths—bony structures that fish use for orientation and detection of movement—and compared these changes to temperature trends across the species’ distribution. Increasing temperatures coincide with increased growth for populations in the middle of the species range, but with reduced growth for those at the warm northern edge of the species’ distribution, indicating that temperatures may have already reached levels associated with increased metabolic costs. If warming continues, the direct metabolic effects of increasing temperatures on this species may lead to declining productivity and range contraction.

Characterizing environmental effects on copepod production and their ecological roles is complicated by multiple physical (e.g. temperature) and biological (e.g. food, predation) factors controlling multiple aspects of copepod physiology and demography. For example, data for two regions in eastern Canada (St. John’s, Newfoundland and Halifax, Nova Scotia) indicate that subtle differences in environmental conditions lead to significant differences in seasonal copepod (Calanus finmarchicus) recruitment timing and magnitude. Here, we quantify how environmental variability influences C. finmarchicus physiology and demography leading to observed regional and seasonal variations in abundance off St. John’s and Halifax. We apply a stochastic individual-based model (IBM) for copepod population dynamics to simulate the seasonal variation in C. finmarchicus abundance of egg through copepodite 1 (C1) stages at the two sites using year-specific local forcing from multi-year data. The model includes individual variability in development, egg production and mortality rates with resulting seasonal C1 abundance averaged among years and compared to analogous observations. We find temperature has a dominant effect on both development and egg production rates while egg recruitment is affected by temperature and female abundance at both sites. We show that mortality rate characterization has a strong influence on modeled abundances, and site-specific environmentally dependent mortality rates are necessary to produce results consistent with observations (temperature vs. food vs. cannibalism via females). Results indicate that prediction of climate change effects on copepod abundance and their ecological roles requires consideration of biological (e.g. chlorophyll a, female abundance) as well as physical (e.g. temperature) factors. In particular, estimates of abundances during the onset of C1 recruitment (i.e. their arrival on the larval fish prey field) are improved by 67–94% when the influence of biological factors on mortality rates are considered.

Factors affecting size-at-age in fish populations include temperature and fishing where the latter can represent a strong selective force on size-at-age variation through changes in population growth and maturation. Over the past three decades, Scotian Shelf haddock ( Melanogrammus aeglefinus ) exhibited declines in maturation timing and mature fish length-at-age. Here, we examine these declines with respect to temperature, stock biomass, and fishing. We employ the thermal integral (growing degree-day, GDD, °C·day) to examine the variation in length-at-age (length-at-day, LaD, cm) and maturity (age-at-50%-maturity) that is attributable to temperature. Unexplained variation in LaD and age-at-50%-maturity remains and is characterized by declines in the LaD-at-GDD regression parameters and the thermal constant for maturity with increasing year-class. We find no significant correlation between the temperature-independent declines in LaD and stock biomass. The combination of high fishing mortality (favouring early maturation) and sustained harvesting of large fish (fast-growing, late-maturing individuals) offers the simplest explanation for the systematic decline in inferred growth and age-at-maturity for Scotian Shelf haddock. These results are consistent with other exploited populations and recent laboratory experiments quantifying the effects of fishing on size-at-age and age-at-maturity.

Traditional plankton models do not simulate the life history, physiology or phenology of mesozooplankton with sufficient realism to represent their ecological roles and associated environmental dependencies. In contrast, individual-based models (IBMs) have proven utility in characterizing fish population dynamics as they bridge the gap between the level at which environmental impacts occur (individuals) and the level at which observations are made (populations). IBMs are under-utilized in zooplankton ecology, possibly because of their apparent complexity, reliance on uncertain parameters, and/or computational expense. Here, we show that such limitations are not inherent, and in fact, IBMs can offer considerable power for quantitative hypothesis testing. We present a conceptually and programmatically simple approach for building a stochastic stage-based IBM for copepods (abundant mesozooplankters). Our model incorporates physiological rates that vary with environmental conditions, and includes stochasticity via a “Fitness” parameter, which characterizes individual variability, and may be prescribed a priori (e.g. genetic), or solved dynamically based on individual history, condition, environment, etc. We demonstrate how this Fitness allows for easy evaluation of the relative importance of forcing factors (e.g. temperature vs. food) on modelled rates and abundances as well as statistical comparison to observations. The latter is a powerful feature of our modelling approach, which we exploit to test hypotheses regarding the seasonal dynamics of the copepod Calanus finmarchicus in the northwest Atlantic as a case study. The result is a model description (including flow chart and code) that can be adapted for a wide range of species and novel applications in a quantitative manner.

Throughout the North Atlantic, the copepod Calanus finmarchicus dominates the zooplankton biomass, linking primary production and higher trophic levels. On Georges Bank, the peak abundance of larval (naupliar) stages occurs in March–April and represents a potential source of prey for cod and haddock larvae. Following this maximum, naupliar abundance declines dramatically, reaching a minimum in May and increasing again in June. Explaining the naupliar seasonal cycle is critical for predicting climate effects on C. finmarchicus dynamics, including whether environmental variability may lead to a mismatch with larval fish. Here, an age-within-stage population dynamics model is used to investigate the factors controlling the temporal variation of C. finmarchicus nauplii in three Georges Bank sub-regions. The model incorporates temperature- and food-dependent development and egg production, as well as female abundance derived from the US Global Ocean Ecosystem Dynamics (GLOBEC) program. Use of field-estimated constant mortality rates overestimates May abundances by as much as an order of magnitude. These data/model discrepancies can not be explained by temperature or food-limitation effects on physiological rates. Instead, accurate simulation requires use of time-varying early stage mortalities, which differ from published estimates in both magnitude and trend. These mortality rates are correlated with C. finmarchicus female abundance, implying cannibalism as a possible regulatory factor. Thus, the biological control of predation (including cannibalism) must be considered to predict the effects of climate on C. finmarchicus and associated larval fish populations.

Modellers have long been aware that the mathematical form of zooplankton mortality, or closure, significantly affects the dynamics of planktonic ecosystem models. Another important formulation is the functional response, i.e. how ingestion rates change with prey density. Here we explain why different grazing responses can have profoundly differing influences on modelled dynamics, and how common practices may limit models due to misguided characterization of feeding behaviours. Use of different ingestion functions in a Nutrient-Phytoplankton-Zooplankton (NPZ) model results in oscillating versus constant densities. Contrary to the conclusions of previous studies, it is shown that these results are not due to zooplankton satiation versus non-satiation. Analysis of a predator-prey model is used to derive the necessary condition for ecological stability, which is related to food-limited clearance rates. Sensitivity studies demonstrate that zooplankton clearance rates have a strong influence on the dynamics of more complex models. Moreover, it is shown that acclimation time lags can dramatically alter results from those where zooplankton instantly adapt to changing prey densities due to the corollary effect on clearance rates. These results are discussed in terms of practical advice to modellers who face uncertainty in choosing expressions for the functional response.

Gentleman, W. C., Neuheimer, A. B., and Campbell, R. G. 2008. Modelling copepod development: current limitations and a new realistic approach. – ICES Journal of Marine Science, 65: 399–413. To predict the influence of environmental variability on copepod dynamics and production, models must account for the effects of temperature and food on stage-dependent time-scales. Here, data for development-time means and variance of Calanus finmarchicus are used to quantify the limitations of existing models. Weight-based individual models are sensitive to uncertain parameters, such as moulting weights, assimilation efficiency, and environmental dependencies, making them highly difficult to calibrate. The accuracy of stage-based population models using ordinary differential equations depends on model structure, with some predicted generation times being incorrect by months. Even when large numbers of age classes are used to reduce modelled variability, it is not possible to make variability consistent with the data. Accuracy of mean times for stage-based population models using difference equations requires a small time-step, which results in large numbers of age classes and modelled variability that is underestimated by orders of magnitude, unless a probabilistic moult fraction is used. We present a new stage-based individual model that avoids the limitations of other models and successfully represents C. finmarchicus mean development timing and associated variability. This approach can be adapted easily for other species, as well as dynamic environmental conditions.

Growth rate in ectotherms, including most fish, is a function of temperature. For decades, agriculturalists (270+ years) and entomologists (45+ years) have recognized the thermal integral, known as the growing degree-day (GDD, °C·day), to be a reliable predictor of growth and development. Fish and fisheries researchers have yet to widely acknowledge the power of the GDD in explaining growth and development among fishes. We demonstrate that fish length-at-day (LaD), in most cases prior to maturation, is a strong linear function of the GDD metric that can explain >92% of the variation in LaD among 41 data sets representing nine fish species drawn from marine and freshwater environments, temperate and tropical climes, constant and variable temperature regimes, and laboratory and field studies. The GDD demonstrates explanatory power across large spatial scales, e.g., 93% of the variation in LaD for age-2 to -4 Atlantic cod (Gadus morhua) across their entire range (17 stocks) is explained by one simple GDD function. Moreover, GDD can explain much of the variation in fish egg development time and in aquatic invertebrate (crab) size-at-age. Our analysis extends the well-established and physiologically relevant GDD metric to fish where, relative to conventional time-based methods, it provides greater explanatory power.

The purpose of this dataset was to compile adult and offspring size estimates for marine organisms. Adult and offspring size estimates of 408 species were compiled from the literature covering17 orders of magnitude in body mass and including Cephalopoda (ink fish), Cnidaria ("jelly" fish), Crustaceans, Ctenophora (comb jellies), Elasmobranchii (cartilaginous fish), Mammalia (mammals), Sagittoidea (arrow worms) and Teleost (i.e., Actinopterygii, bony fish). Individual size estimates were converted to standardized size estimates (carbon weight, g) to allow for among-group comparisons. This required a number of size estimates to be converted and a compilation of conversion factors obtained from the literature are also presented.

While growth variation in fishes is the result of a number of different factors (temperature, food consumption, genetic composition, etc.), temperature has been identified as one controlling factor on fish sizeat-age. Thus, variation in size-at-age due to variation in temperature should be explained before the other factors are explored. We argue that the relevant metric for explaining temperature-dependent size-at-age variation in most fishes is physiologically relevant temperature; i.e., the thermal integral parameterized as the growing degree-day (GDD, oC × d) metric. Accordingly, we employ GDD to examine the change in size-at-age (length-at-day, LaD) among eastern Scotian Shelf (Northwest Atlantic Fisheries Organization statistical divisions 4VW) haddock (Melanogrammus aeglefinus ) from 1970 through 2003. Significant varia tion in length-at-day (LaD) among year classes (decline in slopes and intercepts of LaD-at-GDD relations) remains after LaD variation due to GDD (temperature) is explained. The unexplained variation is postulated to be a result of temperature-independent factors such as condition or size-selective fishing or both.