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Anthropogenic noise pollution is an emerging global threat to fish populations. Among a suite of deleterious effects, noise can potentially impede reproductive success in some fishes by masking their mate advertisement vocalizations. Using the plainfin midshipman fish, Porichthys notatus, a marine toadfish that produces a distinctive ‘hum’ during courtship, we investigated how noise affects male vocalizations and spawning success in the wild. We recorded nesting males for 3 days and measured the frequency (i.e. pitch), amplitude and duration of their vocalizations before, during and after exposure to artificial noise (∼118 Hz tone). We also counted eggs in nests exposed to 10 days of artificial noise versus control nests that were not exposed to artificial noise. Males exposed to noise produced fewer vocalizations, reduced the frequency of vocalizations and increased the amplitude of their mating hum (Lombard effect). However, chronic artificial noise exposure did not significantly affect spawning success, suggesting that the Lombard effect allowed males to sustain clear advertisement signals when competing with a relatively weak artificial noise source. Future studies are needed to determine whether such vocal adjustments incur costs for males, and how common anthropogenic noises, such as boat engines, affect spawning and reproductive success.

Gelatinous zooplankton (GZ) can impact productivity of marine ecosystems through competition with small pelagic fish and predation on early life history stages of species from multiple trophic levels. Nevertheless, GZ do not always represent ‘trophic dead ends.’ Some predators directly consume GZ, and many species host parasitoids which in turn are prey for other organisms. We characterized trophic relationships between the fried-egg jellyfish Phacellophora camtschatica, its hyperiid amphipod parasite (Hyperia medusarum), and juvenile Chinook Salmon Oncorhynchus tshawytscha in the Salish Sea. Hyperia medusarum occurred in 29–47% of Chinook Salmon stomachs over 3 years and were observed in high abundance on P. camtschatica medusae (mean = 428 individuals per medusa). Light and transmission electron microscopy confirmed the presence of morphologically similar nematocysts in the foreguts of H. medusarum from both medusae and Chinook Salmon stomachs. Occurrence of H. medusarum in Chinook Salmon diets was also positively related to an index of P. camtschatica abundance. Chinook Salmon stomachs contained almost exclusively mature female H. medusarum while males and juveniles were common on medusae. Size and sex ratio differences between hyperiids in Chinook Salmon diets and on medusae could reflect predator selectivity or sex and/or life-stage specific differences in H. medusarum behavior. Our results support previous speculation that GZ abundance may facilitate predation on hyperiids by Pacific Salmon. Hyperiid-mediated energy flow from GZ to fish is not limited to medusa-associated fish species and should be considered in studies of marine food webs.

Many small pelagic fish species exhibit dramatic fluctuations in abundance accompanied by range expansions during periods of favorable environmental conditions. The location and extent of suitable habitats also shift in response to both short term variability and long term trends in climate. Near the margins of a contemporary range, trends in abundance may reflect a continuation of historical variability but may also foreshadow future changes in distribution. The Salish Sea (all inland marine waters of Washington State and southern British Columbia; made up of the Strait of Georgia, Strait of Juan de Fuca, and Puget Sound) is a highly productive estuarine system at the northern end of the distribution of Northern Anchovy (Engraulis mordax). An apparent recent (2014–2016) increase in Northern Anchovy abundance has generated interest in the dynamics of this species in the Salish Sea. We compiled recent and historical data to understand spatiotemporal patterns of distribution and fluctuations in abundance over the last century. Spatially-consistent occurrence of eggs, larvae, and juveniles, and year-round presence of multiple age classes, confirm that successful spawning and recruitment of Northern Anchovy occurs within the Salish Sea. Most periods of elevated Northern Anchovy abundance in the last century have corresponded to, or lagged, periods of elevated ocean temperatures. While a 2005 peak in abundance within the Salish Sea also corresponded to higher abundance of Northern Anchovy in adjacent regions of the coastal Pacific Ocean, it seems unlikely that Salish Sea abundance is controlled primarily by advection or migration from external populations. Persistence of elevated ocean temperatures like those observed from 2014 to 2016 could lead to consistently high abundance of Northern Anchovy within the Salish Sea, with implications for trophic relationships and ecosystem function.

Large scale dams have numerous significant impacts on river and nearshore components of watersheds. Large scale dam removal is therefore an increasingly useful restoration tool that reestablishes physical processes and habitats that form nearshore ecosystems. Removing large scale dams will likely affect the functional ecology of nearshore ecosystems, but this concept has yet to be explored. Here we use data from a decade long study to define how the functional ecology of fish responded to large scale dam removal. Dam removal resulted in shifts in the nearshore through the reconnection of riverine and marine hydrodynamic system, large-scale and rapid creation of nearshore habitats, and a shift in nearshore habitats from tidally influenced to non-tidally influenced habitats. The functional diversity of the fish community within the system restored by dam removal was volatile during and after dam removal. Dam removal released sediment that formed new lower river and estuary. These new nearshore habitats supported a fish community of significantly greater functional dispersion and entropy relative to previously present beaches within and outside the new delta. That is, species unique in their diet, habitat use, morphology, and size were abundant relative to less functionally unique fish in newly formed beaches. These trends were temporary as there were no significant differences in functional diversity or entropy of fishes among sites after the restoration. Newly formed habitats proved to be more diverse but had lower resiliency after dam removal. Newly establishing nearshore sites appear more vulnerable to non-native and nuisance species that could disrupt the establishment of the watershed and shoreline. While functional richness at the original estuary sites dropped dramatically after dam removal, resiliency was higher after dam removal corresponding to a shift from estuary to lower river side channel habitat, indicating a more stable nearshore zone than new sites. We anticipate that functional diversity at the newly formed nearshore areas will stabilize as the habitats are vegetated and mature.

Accumulations of beach-cast seaweeds and other debris, collectively known as wrack, are a common and ecologically important occurrence along coastal regions worldwide. As the rate of seaweed introductions continues to increase, so too does their beach-cast collection for aesthetic or commercial purposes. The ecological effects of these harvests are poorly characterized in the literature, especially for nutrient-rich regions such as the Northeast Pacific. Within the southern extremity of Baynes Sound, British Columbia, beach wrack contains an introduced species of red alga called Mazzaella japonica, which became the target of a commercial beach-cast harvest in 2007. The objectives of this research were threefold: 1) to quantify the contribution of M. japonica to wrack inputs within the harvest region; 2) to explore how wrack characteristics influence macrofauna communities; and 3) to determine if the commercial removal of beach-cast seaweeds has a detectable effect on wrack characteristics and macrofauna communities. To answer these questions we monitored a series of permanent transects at six sites across the harvest region from November 2014 until March 2015. We recorded as much as 853 kg (±173 SD) of wrack per meter of shoreline, approximately 90% of which was M. japonica. Despite the removal of 675 tonnes of beach-cast seaweeds, we found that the trends in wrack biomass were similar between both harvested and unharvested locations. Macrofauna communities differed between study sites, as well as with the age class, and depth of the wrack from which they were sampled. These findings contribute to the limited literature on beach-cast seaweed harvesting and provide an important record of M. japonica wrack inputs for future research or monitoring of this non-indigenous seaweed.

Marine protected areas (MPAs) can be useful for conservation efforts, yet the effectiveness of MPAs relies on their size and location, as well as the spatial ecology of the focal species. We investigated the effectiveness of a small MPA adjacent to Cape Cod, MA (USA) for protecting American horseshoe crabs (Limulus polyphemus). We used a fixed acoustic telemetry array to study the spatial ecology of 24 adult horseshoe crabs off the coast of Chatham, Massachusetts, from June 2010 to November 2011. Two groups of horseshoe crabs were tagged in spawning habitats (separated by ∼2.0 km) with differing commercial harvesting pressure: one group inside Stage Harbor where harvesting is permitted, and the other within Monomoy National Wildlife Refuge and the Cape Cod National Seashore (the MPA) where harvesting is prohibited. In the first year of study, crabs tagged in the MPA did not go to Stage Harbor, but instead remained in the MPA and adjacent high-energy beach, whereas crabs tagged in Stage Harbor moved throughout the entire study area. In the second year of study, crabs from both tagging locations used all areas. All crabs generally moved greater distances in the MPA than in other areas, and the majority of movement we recorded was in late spring and summer. All crabs that we tagged used similar areas around Cape Cod. The MPA only provides protection when crabs are in that area, which may only be for a few months of the year. Given that all crabs used Stage Harbor, they were all exposed to potential harvest, but the MPA did provide some protection for all crabs.

A rapidly expanding human footprint - comprised of anthropogenic land-use change and infrastructure - is profoundly affecting wildlife distributions worldwide. Cumulative effects management (CEM) is a regional approach that seeks to manage combined effects of the human footprint on biodiversity across large spatial scales. Challenges to implementing this approach include a lack of ecological data at large spatial scales, the high cost of monitoring multiple indicators, and the need to manage multiple footprints across industries. To inform development of effective CEM, we used large mammals as indicators to address the following questions: a) do species respond more strongly to individual footprint features or to cumulative effects (combined area of all footprint types, measured as total footprint), b) which features elicit the strongest responses across species, and c) are the direction of responses to footprint consistent? We used data from 12 years of snowtrack surveys (2001-2013) in the boreal forest of Alberta, coupled with regional footprint and landcover data, to develop generalized linear mixed-effects models relating the relative abundance of five boreal mammals [gray wolf (Canis lupus), Canada lynx (Lynx canadensis), coyote (Canis latrans), white-tailed deer (Odocoileus virginianus) and moose (Alces alces)] to individual and cumulative effects of the human footprint. We found that across species the strongest responses were to agriculture, roads, and young cutblocks (

The usefulness of the apparent redox potential discontinuity (aRPD) in assessments of marine benthic habitat quality was explored at two intertidal mudflats along the north Pacific coast of Canada. Two transects were established at each intertidal site, with three sediment biogeochemistry cores collected from each transect four times over the summer of 2016. Measurements of the sediment pore water dissolved oxygen (DO) content and redox (Eh) conditions were taken at the surface of the core (measured vertically), as well as at increasing depths (1 cm between readings) into the sediment (measured horizontally through predrilled holes in the biogeochemistry corer). While oxic, anoxic, oxidized, and reduced sediment pore water was observed above and below the aRPD, in general, sediment above the aRPD had higher DO content, and higher Eh values than sediment below the aRPD. Therefore, the aRPD depth can be used as a relative indicator of sediment pore water DO and Eh conditions: sediment with a deeper aRPD depth has more available DO, and the pore water has higher Eh values (more oxidized or less reduced) than sediment with a shallower aRPD depth. As such, the aRPD depth is a useful parameter to include in models that assess the quality of marine benthic habitats.

Development of tools for early detection of invasive species is critically important as the threat of global invasions increase. Early detection as applied to invasive species is a system of active and passive surveillance to find and verify the identity of new invaders as quickly and efficiently as possible. The earlier such species can be detected the more feasible their control and potential eradication will be. A sensor is a device that detects or measures a physical or biological property (here an invasive species), and records, indicates or responds to it. Here, I summarize what features of visual and acoustic sensors make effective tools for early detection of invasives, and suggest future potential for their use. Visual sensors are by far the dominant mode of detection, particularly in terrestrial habitats. At small scales they include photography and video technology along with the advent of advanced image acquisition and automatic identification. At larger scales remote sensing by use of drones, satellites and video technology are being developed to map invasive species habitats in both terrestrial and aquatic environments. Future use will depend in part on further development of automatic detection methodology. There is also large potential in the use of acoustic methods for early detection of invasives, especially cryptic ones, but such technology is still in its infancy due to technological and analytic limitations. In conclusion, the use of visual and acoustic sensors holds much promise for detecting and monitoring invasive species, particularly in remote settings.

As global temperatures increase and dissolved oxygen (DO) content decreases in marine systems, indices assessing sediment DO content in benthic habitats are becoming increasingly useful. One such measure is the depth to the apparent redox potential discontinuity (aRPD), a transition of sediment color that serves as a relative measure of sediment DO content. We examined spatiotemporal variation of aRPD depth, and the nature of the relationships between aRPD depth and biotic (infauna and epibenthic predators) and abiotic variables (sediment properties), as well as the availability of resources (chlorophyll a concentration, and organic matter content) in the intertidal mudflats of the Bay of Fundy, Canada. aRPD depth varied significantly through space and time, and a combination of biotic (sessile and errant infauna, as well as epibenthic predators), and abiotic (exposure time of a plot, sediment particle size, penetrability, and water content) variables, as well as the availability of resources (sediment organic matter content, and chlorophyll a concentration) were correlated with aRPD depth. As such, knowledge of both biotic and abiotic variables are required for a holistic understanding of sediment DO conditions. Abiotic variables likely dictate a suite of potential aRPD depth conditions, while biota and resource availability, via bioturbation and respiration, strongly influence the observed aRPD depth. As DO conditions in marine systems will continue to change due to global climate change, elucidating these relationships are a key first step in predicting the influence decreasing DO content may have upon marine benthos.

The Intermediate Disturbance Hypothesis (IDH) predicts that disturbances of an intermediate frequency or intensity will maximize community biodiversity/richness. Once almost universally accepted, controversy now surrounds this hypothesis, and there have even been calls for its abandonment. Therefore, we experimentally evaluated if an infaunal community along the north coast of British Columbia, Canada, would respond to disturbances as predicted by the IDH. The characteristics of this soft-sediment intertidal mudflat (productivity, species pool, population growth rate) maximized our chances of finding evidence to support the IDH. More specifically, we tested if intermediate severities and frequencies of disturbance maximized infaunal community richness by mechanically disturbing sediment, and varying the intensity (0%, 25%, 50%, 75%, and 100% of the surface area of a plot disturbed) and frequency of sediment disturbance (never, once, twice, and every week during a four week period). No effect of frequency or intensity of sediment disturbance on community richness was observed. Further, none of our experimental treatments were statistically different than the controls. This is likely due to the subtle difference between successional stages in this soft-sediment habitat (difference of less than one taxa between treatments). Therefore, in habitats whose productivity, regional species pool, and population growth rates would otherwise suggest a response to disturbances as predicted by the IDH, minor differences between successional stages may result in richness patterns that deviate from those predicted by the IDH.

Microplastic contamination is a growing threat facing marine ecosystems, of which a prominent source is the fibres from synthetic clothing. Ingestion and egestion (excretion) of microfibres, and whether these have short-term effects on behaviours such as feeding rate, have yet to be studied in many organisms, especially non-bivalve filter feeders. To determine if a common, filter feeding, intertidal invertebrate can ingest microfibres, we studied the acorn barnacle (Balanus glandula Darwin 1854). We collected B. glandula from four locations near Bamfield, British Columbia, Canada, exposed half of them to a high concentration (~70,000 microfibres/L) of brightly coloured polyester microfibres for 24 h in unfiltered seawater (while the other half received a non-exposure treatment), and measured the feeding rates of the barnacles before and after the exposure. An average of 1.2 ± 1.9 fibres per barnacle were present in the gastrointestinal tracts of the plastic treatment group before depuration, and 0.3 ± 0.6 fibres per barnacle were found in the corresponding control group. Prior to depuration, 50% of the 20 barnacles in the plastic treatment ingested at least one microfibre, while a 15% ingestion rate was observed in the control group. There was no detectable short-term effect of microfibre ingestion on feeding rate. A 48-h post plastic exposure depuration period was used to evaluate whether microplastics were egested. No difference in egestion was found between those assessed directly after exposure and those that underwent depuration. Furthermore, a low depuration rate of 0.05 microfibres per 48 h suggests that barnacles may require longer than 48 h to egest microfibres. If representative, these results indicate that acorn barnacles ingested few microfibres even when exposed at very high concentrations, which supports the idea that they are at low risk for microplastic contamination and would not be a suitable indicator species.

Microplastic particles (MPs) occur widely in aquatic ecosystems and are ingested by a wide range of organisms. While trophic transfer of MPs is known to occur, researchers do not yet fully understand the fate of MPs in food webs. We explored the factors influencing reported ingestion of MPs in marine and freshwater fishes by conducting a literature review of 123 studies published between January 2011 and June 2020. We used Bayesian generalized linear mixed models to determine whether MP ingestion by fishes varies by Food and Agricultural Organization fishing area, trophic level, body size, taxa, and study methodology. After accounting for methodology, strong regional differences were not present, although ingested MP concentrations were slightly different among some FAO areas. According to the reviewed studies, MP concentrations in fish digestive tracts did not increase with either trophic level or body size, suggesting that biomagnification of MPs did not occur, although larger fish were more likely to contain MPs. Researchers reported higher concentrations of MPs in clupeids compared with other commonly studied taxonomic families, which could be due to their planktivorous feeding strategy. Methodology played an influential role in predicting reported concentrations, highlighting the need to harmonize methods among studies.

Density-dependent settlement, growth and mortality are often the major factors controlling recruitment success of recently-settled marine fishes. During this stage, juvenile fishes generally have spatial refuges from predation, and forage in limited but risky areas near refuges. Little is known about the mechanisms by which the tradeoff between feeding and refuge use lead to density dependent mortality. Foraging arena theory predicts that feeding activity should depend strongly on juvenile density and predation risk. Selection should act on the time that juveniles spend foraging, so as to strike a balance between growth and mortality. Because the risk of predation also varies with habitat, it is expected that variation in foraging times and resulting growth and mortality rates will be habitat-specific and density-dependent. This study tested these concepts by respirometric measurement of the metabolic cost of feeding and shelter site defense in young-of-year cunner (Tautogolabrus adspersus) in the northwest Atlantic. Metabolic costs were applied to time budgets measured in the field to estimate in-situ energy budgets. Contrary to expectation, time and energy spent on foraging increased as habitat complexity or conspecific density decreased. Time and energy spent on refuge defense increased with increasing predation risk (as mediated by habitat complexity) or conspecific density, highlighting the importance of refuge for a species that enters torpor at night and during the winter. Future recruitment studies should include examination of spatial habitat use by juveniles, and the behavioral and physiological mechanisms for adjusting behavior to varying food density and predation risk.

The existence of fine-scale structure in the abiotic and biotic characteristics of pelagic habitats is widely recognized, but the ecological significance of that structure is understudied. Logistical considerations have meant that research on the ecology of commercially and ecologically important marine species generally occurs at relatively coarse spatial and temporal scales. Many populations of Chinook Salmon (Oncorhynchus tshawytscha) in the Northeast Pacific are currently experiencing low productivity. The hypothesis that survival, and hence recruitment, of Chinook Salmon is related to growth early in marine residence has led to intensive research on the trophic ecology of this species during the first year at sea. We employed a small vessel-based methodology to simultaneously characterize fine-scale spatial and temporal variation in physical and biological oceanography, and juvenile Chinook Salmon distribution, size, diet, temperature exposure, and growth from July through October at five sites within the Southern Gulf Islands of the Salish Sea. Densities of zooplankton prey of Chinook Salmon declined to very low levels by the end of the study period. Juvenile Chinook Salmon stomach fullness and growth also declined by early fall while frequency of empty stomachs and importance of fish in diets increased. We found that both oceanographic conditions and trophic ecology of juvenile Chinook Salmon varied among sites only a few (2–23) kilometers apart. Juvenile Chinook Salmon were larger and faster growing at sites where fish (generally Pacific Herring Clupea pallasii) constituted a larger proportion of the diet. Overall, the most important prey of juvenile Chinook Salmon by mass proportion (25.6%) was Pacific Herring; however, only 8.4% of individuals contained C. pallasii. Analysis of co-occurrence of diet items suggested alternate foraging strategies, with some individuals specializing on Pacific Herring while others targeted a variety of small crustacean zooplankton. Juvenile Chinook Salmon which had consumed Pacific Herring had greater mean stomach fullness than those which had not. Predation on Pacific Herring was strongly related to juvenile salmon length, suggesting that age-0 Pacific Herring may have been too large to be consumed by smaller Chinook Salmon. Our results reinforce the importance of the transition to piscivory in the trophic ecology of juvenile Chinook Salmon. Further research is necessary to determine if fine-scale distribution of larger, piscivorous juvenile salmon is linked to the distribution of their forage fish prey and to understand the role of prey to predator size ratios in limiting the ability of juvenile salmon to transition to piscivory.

Underwater noise pollution is a recognized threat to marine life. In British Columbia, Canada, Pacific rockfish (Sebastes spp.) were historically overfished, prompting the establishment of Rockfish Conservation Areas (RCAs). However, there are no restrictions prohibiting vessel transits in RCAs. We hypothesized that RCAs do not protect rockfish from sub-lethal harm from noise. We compared noise levels at three RCAs with adjacent unprotected reference sites from August 2018–June 2019. While RCAs had lower levels of noise overall than reference sites, this trend was inconsistent; some RCA sites had higher levels of noise during certain time periods than non-RCA sites. A vessel noise detector was the best predictor of noise level over three frequency bands (20–100 Hz, 100–1000 Hz, 1–10 kHz), and predicted sound levels which could mask rockfish communication. We conclude that RCAs do not reliably protect rockfish from noise pollution, and recommend further study into potential impacts on stock recovery.

Benthic invertebrate communities are reliable indicators of environmental conditions, and thus often assessed during ecological studies. However, when identifying all specimens to the same taxonomic unit is not possible, the common practice of identifying each specimen to the lowest possible taxonomic level may introduce enough taxonomic noise into datasets to obscure important trends. Using an infaunal-invertebrate community from the Cassiar Cannery mudflat (British Columbia, Canada), we tested if identifying specimens to different taxonomic levels (order, family, genus, species, and lowest possible) produced different statistical interpretations, or observed magnitude of differences in community structure and density between microhabitats. When taxonomic level was varied, statistical interpretations and magnitude of observed differences did not differ. Given the resources required to train taxonomists, and the time required to identify all specimens to species, identifying invertebrates to broader levels may represent an efficient trade-off between taxonomic resolution and resources. This study also showed no difference in conclusions between identifying specimens to species or to the lowest possible taxonomic unit, a mixture of taxonomic resolutions (phylum, class, order, species, etc.). In situations where it is not possible to identify all specimens to species, identifying specimens to the lowest possible unit may offer a similar resolution as would have been achieved with species level investigations.

Estuarine ecosystems are degraded through anthropogenic development, leading to reduced habitat suitability for biological communities. The Skeena River estuary (British Columbia, Canada) is undergoing passive reclamation from historical salmon canneries and pulp mills, while localized disturbances continue at present. To reveal both current impacts and the trajectory of passive reclamation from historical activities, the intertidal mudflat surrounding the longest operating salmon cannery, Cassiar Cannery, within the Skeena estuary was surveyed. Nutrient availability (chlorophyll a concentration/organic matter content), sediment variables (particle size, water content, penetrability, woody debris/macroalgae cover, apparent redox potential discontinuity depth), and infaunal community composition varied spatiotemporally, and suggest that an old dock may be influencing the infaunal community given the abundance of disturbance indicating taxa below the dock. However, with populations of amphipods, mobile polychaetes, and a complex community structure, the mudflat as a whole appears to be relatively healthy. Therefore, cessation of historic activities has allowed for passive reclamation to a reasonably unstressed state, though a threshold of recovery may exist for intertidal mudflats beyond which passive reclamation will not be effective.

Trophic pathways and size-based bioaccumulation rates of total mercury were evaluated among recreationally caught albacore tuna (Thunnus alalunga), yellowfin tuna (Thunnus albacares), shortfin mako shark (Isurus oxyrinchus), thresher shark (Alopias vulpinus), and dolphinfish (Coryphaena hippurus) from offshore southern New England waters of the northwest Atlantic Ocean between 2008 and 2011. Mercury concentrations were highest in mako (2.65 ± 1.16 ppm) and thresher sharks (0.87 ± 0.71 ppm), and significantly lower in teleosts (albacore, 0.45 ± 0.14 ppm; yellowfin, 0.32 ± 0.09 ppm; dolphinfish, 0.20 ± 0.17 ppm). The relationship between body size and mercury concentration was positive and linear for tunas, and positive and exponential for sharks and dolphinfish. Mercury increased exponentially with δ 15N values, a proxy for trophic position, across all species. Results demonstrate mercury levels are positively related to size, diet and trophic position in sharks, tunas, and dolphinfish, and the majority of fishes exhibited concentrations greater than the US EPA recommended limit.

Our understanding of the significance of sound production to the ecology of deep-sea fish communities has improved little since anatomical surveys in the 1950s first suggested that sound production is widespread among slope-water fishes. The recent implementation of cabled ocean observatory networks around the world that include passive acoustic recording instruments provides scientists an opportunity to search for evidence of deep-sea fish sounds. We examined deep-sea acoustic recordings made at the NEPTUNE Canada Barkley Canyon Axis Pod (985 m) located off the west coast of Vancouver Island in the Northeast Pacific between June 2010 and May 2011 to determine the presence of fish sounds. A subset of over 300 5-min files was examined by selecting one day each month and analyzing one file for each hour over the 24 h day. Despite the frequent occurrence of marine mammal sounds, no examples of fish sounds were identified. However, we report examples of isolated unknown sounds that might be produced by fish, invertebrates, or more likely marine mammals. This finding is in direct contrast to recent smaller studies in the Atlantic where potential fish sounds appear to be more common. A review of the literature indicates 32 species found off British Columbia that potentially produce sound could occur in depths greater than 700 m but of these only Anoplopoma fimbria and Coryphaenoides spp. have been previously reported at the site. The lack of fish sounds observed here may be directly related to the low diversity and abundance of fishes present at the Barkley Canyon site. Other contributing factors include possible masking of low amplitude biological signals by self-generated noise from the platform instrumentation and ship noise. We suggest that examination of data both from noise-reduced ocean observatories around the world and from dedicated instrument surveys designed to search for deep-sea fish sounds to provide a larger-scale, more conclusive investigation into the role, or potential lack thereof, of sound production.

Mangroves, one of the major coastal ecosystems of tropical and subtropical regions, are critical habitats for fish and crustaceans, and provide a number of ecosystem services to people. While mangrove uses have been widely documented based on local ecological knowledge, seldom has this approach been used to analyse the mangrove-fishery relationship. By conducting semi-structured interviews (n = 82) with fishers in three different villages surrounding the Cienaga Grande de Santa Marta, the most important lagoon system in the Colombian Caribbean because of its size and productivity, we evaluated fishing activity over time, mangrove use and mangrove-fishery linkage, and fishing and gear spatial distribution. Respondents believed that mangroves are critical habitats for fishery resources because they function as nurseries, food source and reproduction areas, and considered that the resource would be in jeopardy in the absence of mangroves. While fishing is the main activity in mangroves, they are also used for firewood, construction and to make fishing gear, but how fishers use mangroves varies across villages. Fishing is concentrated close to mangroves (

Population assessment techniques for soft-sediment infauna (invertebrates within the substrate) requires excavation of specimens, damaging or killing the specimen and surrounding habitat, while being time-consuming and costly. Rapid population assessments of some marine burrowing decapods have been possible by counting burrow openings to estimate abundance, and while they may be used as indicator species, these decapods are not ubiquitous to environments requiring monitoring. Additionally, the presence of other burrowing macrofauna (invertebrates living in the sediment and retained on 1 mm mesh such as clams or large worms) may reduce the efficacy of burrow openings in estimating macrofauna abundance. As such, we assessed mudflats along the north coast of British Columbia, Canada, during summer 2017 to determine if macrofauna abundances could be estimated from burrow openings on the sediment surface in regions of low (n = 1 species) and high (n = 8 species) biodiversity. Abundance could not be estimated at the low diversity sites where only one macrofaunal species created burrows. At the high diversity site, species-specific models estimating abundance from burrow openings could not be constructed; however, the total number of burrow openings observed was useful in estimating total infaunal community abundance. As such, burrow openings may not be an effective tool in assessing species-specific abundances, but may be appropriate to estimate overall community changes.

The distribution and abundance of the canopy-forming kelp Nereocystis luetkeana is of increasing concern for environmental management and conservation in coastal regions due to its importance as a foundation species. Mapping kelp forests aids in understanding their health, productivity, and response to environmental conditions. Remote sensing using satellites is an increasingly accessible tool for mapping nearshore habitats allowing for applications such as long-term monitoring and large- and small-scale surveys. This paper provides a review of passive optical remote sensing techniques for detection and mapping of floating macro-algae, and adapts these techniques for detecting Nereocystis luetkeana, demonstrating their application through a comprehensive case study, from imagery acquisition to map validation. This review with associated case study communicates to non-remote sensing experts a road map to use remote sensing technology for mapping kelp habitats. Keywords: Kelp, Remote sensing, Habitat mapping, Macro algae, Digital image processing, Review

Large pelagic predators were used as biological samplers to gain information on cephalopod diversity, abundance, distribution, and their role as prey in the Northwest Atlantic Ocean. Fish predators were caught by recreational anglers in offshore waters of New England (NE; 2007–2010), the Mid-Atlantic Bight (MAB; 2009–2010) and the South Atlantic Bight (SAB; 2010–2011). In total, 2362 cephalopods, including 22 species of squid and 4 octopods, were identified in the diets of 13 species of predatory fishes. Cephalopod body sizes were obtained for 1973 specimens through direct measurement of mantle lengths (ML) or estimated using lower rostral/hood lengths of lower beaks. Cephalopod diversity (number of species) was highest in predator diets from the SAB ( N =19), intermediate in NE ( N =18), and lowest in the MAB ( N =9); however, differences may reflect unequal sampling effort among regions. The most important cephalopods across predator diets by number and frequency of occurrence were from the families Ommastrephidae, Argonautidae, Loliginidae, and Histioteuthidae. Shortfin squid ( Illex illecebrosus ) and paper nautilus ( Argonauta sp.) were the most recurrent species identified across spatiotemporal scales; size distributions of these two species varied significantly among regions, and the largest individuals on average were found in the MAB. Results demonstrate that although pelagic predators consumed a broad range of cephalopod species, octopods and squids from the families Argonautidae and Ommastrephidae dominated the collective diets of numerous pelagic teleosts and elasmobranchs, and play a key role in offshore food-webs of the Northwest Atlantic Ocean. This study emphasizes the value of using predators as biological samplers to gain information on cephalopod biogeography, and as a potential approach to track ecosystem changes in this region due to environmental and anthropogenic stressors.

a b s t r a c t Species distribution models (SDMs) are currently being used to identify essential fish habitat and guide fisheries management worldwide. We present SDMs based on generalized linear mixed models (GLMM) of the fall distribution or occurrence of juvenile American shad (Alosa sapidissima) and juvenile striped bass (Morone saxatilis) in the Hudson River estuary (HRE) based on data from a fishery-independent survey. The distribution of both species were modeled over a 6-year period (2000-2005) as a function of dissolved oxygen, salinity, water temperature, distance along the HRE denoted as river mile, time or Julian day, distance from submerged aquatic vegetation (SAV), and sediment characteristics. Salinity, river mile, and Julian day were the most important environmental determinants of juvenile American shad presence, and sediment type, salinity, river mile, and Julian day were the most important environmental determinants of juvenile striped bass presence. Calibration plots showed a high level of agreement between predictions generated by each model and actual observations of each species' occurrence. Based on this result, we mapped the predicted distribution of each species. We found the highest predicted probabilities of juve- nile American shad presence in the upper HRE, but the highest predicted probabilities of juvenile striped bass presence were in the lower HRE. Our results suggest that habitat partitioning between these two species is present during the fall in this system but the mechanism is unclear. © 2011 Elsevier B.V. All rights reserved.

Accurate species identification is required for stock assessment to monitor exploited species. Genetic tools are useful for species identification; employing SNP (single nucleotide polymorphisms) as markers, here we describe two cases of species misidentification which may lead to inaccurate estimates of stock size and adversely affect sustainable hake fisheries management in the Atlantic Ocean. North American hakes and African hakes show evidence of erroneous labelling that may obscure exploitation estimates of the species caught together in mixed fisheries (Merluccius albidus and Merluccius bilinearis, and Merluccius capensis and Merluccius paradoxus in North America and Africa respectively). Use of genetic methodology for species identification is recommended for improving accuracy of stock estimates in these two pairs of hakes.

Longfin squid, Loligo pealeii, were exposed to two predators, bluefish, Pomatomus saltatrix, and summer flounder, Paralichthys dentatus, representing cruising and ambush foraging tactics, respectively. During 35 trials, 86 predator–prey interactions were evaluated between bluefish and squid, and in 29 trials, 92 interactions were assessed between flounder and squid. With bluefish, squid predominantly used stay tactics (68.6%, 59/86) as initial responses. The most common stay response was to drop to the bottom, while showing a disruptive body pattern, and remain motionless. In 37.0% (34/92) of interactions with flounder, squid did not detect predators camouflaging on the bottom and showed no reaction prior to being attacked. Squid that did react, used flee tactics more often as initial responses (43.5%, 40/92), including flight with or without inking. When all defence behaviours were considered concurrently, flight was identified as the strongest predictor of squid survival during interactions with each predator. Squid that used flight at any time during an attack sequence had high probabilities of survival with bluefish (65%, 20/31) and flounder (51%, 18/35). The most important deimatic/protean behaviour used by squid was inking. Inking caused bluefish to startle (deimatic) and abandon attacks (probability of survival = 61%, 11/18) and caused flounder to misdirect (protean) attacks towards ink plumes rather than towards squid (probability of survival = 56%, 14/25). These are the first published laboratory experiments to evaluate the survival value of antipredator behaviours in a cephalopod. Results demonstrate that squid vary their defence tactics in response to different predators and that the effectiveness of antipredator behaviours is contingent upon the behavioural characteristics of the predator encountered.

Cephalopods are primary prey to a wide range of predators in marine food-webs, yet a basic understanding of the mechanisms controlling predation risk and demand on their populations is lacking. Feeding experiments were conducted to evaluate how relative prey size and behavior mediate the susceptibility of squid to predation. Attack and capture of longfin inshore squid ( Loligo pealeii ) were quantified using two predators: bluefish ( Pomatomus saltatrix ) a pelagic, cruising predator, and summer flounder ( Paralichthys dentatus ) a benthic, ambush forager. Predator selectivity, prey susceptibility, and prey profitability were estimated as a function of relative prey size from predator–prey interactions during behavioral trials. Patterns in attack rates suggested that size-selection on squid was constrained by passive processes rather than active choice for both predators. The susceptibility of squid to predation by bluefish was strongly dependent on relative prey size; however, flounder were equally efficient at capturing all sizes of squid offered. Handling times increased exponentially with relative prey size and were the primary constraint on selectivity and profitability in flounder. Prey profitability was a dome-shaped function of relative squid size in both predators. Overall, the relative size and values at which profitability was maximized were higher in bluefish indicating they were the more efficient predator of squid. Squid succumbed to greater time-dependent mortality rates than Atlantic silversides ( Menidia menidia ) and mummichogs ( Fundulus sp .) suggesting that when equal amounts of squid and fish are available in the environment, squid will be selectively ingested by bluefish and flounder. In addition to the influence of relative prey size, predator foraging behaviors and size-dependent encounter rates were thought to be important factors affecting selection on squid in the northwest Atlantic ecosystem.

article i nfo In a series of laboratory experiments, the feeding behaviors of summer flounder (Paralichthys dentatus) were examined in response to squid and fish prey. Attack and capture tactics were evaluated for their influence on capture success, handling time, and prey-type selectivity. The ambush tactic was the primary behavior (50.6%) used to attack squid. Secondary attack types included active pursuit (42.7%) and stalking (6.7%). Regardless of the prey species targeted or the type of attack employed, summer flounder were equally efficient in capturing prey; capture success rates ranged from 50%-83%. The majority of prey were swallowed in a headfirst orientation (55.3% of squid), however swallow alignment did not significantly affect handling time. Approach times during ambush attacks were greater overall in comparison to active attacks, and relative prey size significantly affected capture times. Despite additional costs in handling time, summer flounder actively selected for mummichogs (Fundulus spp.) (attack rate (attacks per minute)=0.11) over longfin squid (Loligo pealeii) (0.08) and Atlantic silversides (Menidia menidia) (0.02). Differential attack rates favoring mummichogs suggests a preference towards demersal prey. In the presence of relatively large, fast- moving, and pelagic prey, summer flounder used a greater diversity of attack tactics than have been observed previously under controlled conditions. The behavioral plasticity exhibited by summer flounder is likely mediated by prey behavior and local availability of prey resources in inshore and offshore environments.

High levels of bidirectional introgressive hybridization were found between the two Atlantic North American hakes Merluccius albidus and M. bilinearis in their overlapping distribution area between the 34 and the 42°N parallels, employing mitochondrial and nuclear DNA markers. Absence of F1 hybrids, and varied levels of bidirectional introgression, indicate long-time hybridization and backcrossing. Based on the evolutionary history of the genus Merluccius, originated in this area from the ancestor of the present M. bilinearis by the rise of the Panama Isthmus, secondary contact between the two species has probably been promoted by northwards displacement of M. albidus. Higher introgression rates in southern areas of M. albidus could be explained by restricted gene flow in that area which may allow long-term accumulation of introgressed genes.

Though fecundity estimation has typically been very time consuming, efficient methods have recently been developed. Building on these developments, we describe procedures for efficiently producing precise, accurate, fecundity estimates for highly fecund Atlantic cod, using a low-cost laboratory setup. Capturing images with a standard flatbed scanner and analyzing them with free image analysis software (total equipment cost ≈ $100) we were able to process individual samples in as little as 5 min. We show a strong relationship between mean oocyte diameter (range 200–900 μm) and oocyte density ( r 2 = 0.971, n = 50), and thus are able to estimate fecundity using gravimetric and auto-diametric methods. Testing the precision of the auto-diametric method we find estimates produced by both methods to be highly correlated ( r 2 = 0.961, n = 26). The success of these methods should assure fisheries scientists that fecundity estimation is no longer the daunting task it once was, and catalyze further production of fecundity data.

Many small fish, including several juvenile Atlantic flatfish, are most abundant in shallow areas presumable because these habitats enhance survivorship and/or growth. In this study, we investigated size-dependent depth distributions and the role of shallow habitats as predator refuges for age-0 winter flounder (Pseudopleuronectes americanus) in a northwest Atlantic estuarine nursery. Analysis of trawl surveys performed during the larval settlement period throughout the Navesink River and Sandy Hook Bay, New Jersey, showed that as fish increased in size, depth of occurrence gradually decreased, so that individuals >35 mm standard length (SL) were concentrated in habitats ∼1 m deep. Tethering in structurally simple and adjacent shallow and deep habitats showed that predation risk for flounder (30–50 mm SL) was low in shallow water (

We conducted a series of size-structured laboratory experiments to quantify and compare the susceptibility of several estuarine and marine forage fishes to attack and capture by piscivorous predators. Size-dependent estimates of capture success, handling time, and prey profitability were generated from single-species experiments offering bay anchovy, Atlantic menhaden, Atlantic silverside, and age-0 striped bass to piscivores. Bay anchovy and Atlantic menhaden were most susceptible to capture and yielded high profitability compared to Atlantic silverside and age-0 striped bass prey. Variation in capture success among forage species was particularly influential in generating disparate profitability functions. Although morphological differences among forage species contributed to variation in susceptibility to predation, behavioral analyses indicated that variable reaction distances to approaching predators and activity levels of prey may explain a large fraction of the observed differences in susceptibility. When several forage species were offered to predators simultaneously in larger enclosures, mortality was highest and occurred earlier for bay anchovy and Atlantic menhaden compared to other prey, which points to the strong influence of predator capture success on overall forage fish vulnerability. Our results demonstrate species-specific differences among forage fishes in the ability to avoid attack and capture by piscivores, and we conclude that the

We analysed micronuclei in brown trout Salmo trutta specimens sampled in the Trubia River, upstream and downstream of the emissions from a Spanish military factory to assess genotoxicity risks derived from military wastes. A significant exponential increase in micronuclei counts was found in fish living downstream of the military wastes with respect to fishes inhabiting upstream areas of the same river. In comparison, we only found a linear increase in micronuclei counts in a control stream where an old military factory had been demolished 6 months before sampling. This difference suggests that active discharge of armament factory wastes can directly induce micronuclei and therefore represents a genotoxic risk for the ecosystem.

Statistical significance and biological significance are not the same thing. For example, given a large enough sample size, any statistical hypothesis test is likely to be statistically significant, almost regardless of the biological importance of the results. Conversely, when the sample size is small, biologically interesting phenomena may be missed because statistical tests are unlikely to yield statistically significant results. Statistical and biological significance can be linked through the use of statistical power analysis. While power analysis is gaining popularity in many branches of biology (reviewed by Fairweather 1991; Taylor & Gerodette 1993; Searcy-Bernal 1994), it has been largely ignored in others, including animal behaviour, despite attempts to draw it to general attention (Greenwood 1993). The purpose of this article is to reinforce Greenwood’s advice by clearly demonstrating the relationship between sample size, biological significance and statistical power and by providing key references to introductory papers, texts and computer software. We use an example from Animal Behaviour to illustrate the importance of power analysis and the consequences of ignoring power. Our example is taken from a recent aquarium study on the willingness of juvenile rainbow trout, Oncorhynchus mykiss, to forage under the risk of predation (Johnsson 1993). As a part of the study, the investigator tested the null hypothesis that large and small juvenile trout do not differ in their susceptibility to predation. To test this hypothesis, eight replicate groups of six large and six small juveniles were exposed one by one to a standardized encounter with a predatory adult trout. On average 19&4.9% (X&) of the large fish and 45&7.0% of the small fish were killed by the predator. The difference between the two size classes was not statistically significant using a Wilcoxon signed-ranks test and a significance criterion of a=0.05 (T=29, N=8, P=0.15). Does this mean that the null hypothesis of no difference should be accepted? Not necessarily: another possibility is that there exists a biologically significant difference in susceptibility to predation in the population, but that the test was not sensitive enough to detect it. Statistical power analysis allows the evaluation of these two alternatives. The statistical power of a test is the probability of getting a statistically significant result, given that the null hypothesis is false. Power is proportional to the sample size, significance criterion (a level) and effect size, and is inversely proportional to the variance in the population. Effect size is a measure of biological significance: it is the difference between the results predicted by the null hypothesis and the actual state of the population being tested. In our example effect size is the difference in probability of predation between size classes. Power analysis can be used to determine whether the experiment had a good chance of producing a statistically significant result if a biologically significant difference existed in the population. In other words, whether the Correspondence: Len Thomas, Centre for Applied Conservation Biology, Faculty of Forestry, No. 270-2357 Main Mall, Vancouver, British Columbia V6T 1Z4, Canada (email: lthomas@unixg.ubc.ca).

Autotomy, the reflex severance of an appendage, is considered an adaptation to avoid predators and limit wounds. While an autotomy response may provide immediate survival benefits, the loss of one or more appendages can result in long-term functional and energetic costs. In this paper, we present an overview of the incidence of limb damage and loss in decapod crustaceans; review the literature on the ecological consequences of such injury; and suggest areas for future research. A survey of limb damage and loss in field populations showed consistently high incidences of injury in 14 reviewed species. Typically, chelipeds were the limb type lost most often and injuries were distributed symmetrically. No consistent correlation existed between injury frequency and body size among species. In general, the frequency of injury was independent of sex and moult stage. Fishery practices were responsible for substantial limb loss in some commercial species. In terms of energetic costs, experiments demonstrated that limb injury could reduce growth increment and affect intermoult duration. Functionally, limb damage was capable of reducing foraging efficiency and mating success, and increasing vulnerability to intra- and interspecific attack. The magnitude of these effects depended on the type and number of limbs lost. Given the prevalence of injury in decapod crustacean populations, the costs involved, and the ecological importance of many crustacean species, nonlethal injury has the potential to affect population dynamics and community processes. Convincing evidence of autotomy's effects beyond the level of the individual, however, is, at present, lacking. Future work should redress this shortcoming. In addition, comparative studies are needed on decapod species from different habitats and with different lifestyles before generalizations can be made about the costs and benefits of autotomy.