The release of hatchery-reared fish is a widely implemented management intervention aimed at supplementing or restoring declining wild populations. In Scandinavian rivers affected by hydropower development, stocking of hatchery‑reared Atlantic salmon (Salmo salar, Linnaeus, 1758) is commonly used to compensate for lost fishing opportunities when natural production losses in rivers are affected by hydropower development. Nevertheless, post-release mortality remains substantial, largely because fish reared under conventional hatchery conditions frequently exhibit insufficient behavioral competence for survival in natural environments, including underdeveloped predator-avoidance responses and suboptimal foraging proficiency. Previous studies suggest that environmental enrichment can promote behavioural development in Atlantic salmon (Salmo salar) parr, particularly when multiple types of enrichment—such as substrate complexity, water flow variation, and visual or structural features—are provided during raring. Here we show that structural enrichment alone after only 11–12 weeks exposure significantly improved feeding success on novel live prey in parr compared to individuals reared in unenriched environments. These findings indicate that relatively simple and short‑term structural enrichment can enhance key foraging abilities in juvenile salmon, with potential implications for improving post‑release performance and survival of hatchery‑reared fish.

Introduction: Intestinal colonisation of Salmonella is a major concern in the poultry industry, and a low dose of the high-purity synthetic capsaicin analogue phenylcapsaicin (PheCap) has the potential to be a phytobiotic alternative to antibiotics in reducing floor Salmonella in commercial broiler chicken houses. In this study we present the first safety assessment of PheCap at doses relevant for the poultry industry. Methods: In a completely randomized block design, Ross 308 male broilers were offered feed containing 0, 10, 15, or 150 mg PheCap/kg. Growth rates, mortality, haematology, clinical chemistry, foot pad lesions, litter quality and gross pathological examination of organs and tissues were evaluated for signs of toxicity over a two-phase, 35-day growth period. Results: No differences in feed intake and broiler growth were found, with broilers in the control group having the highest mortality. There was a statistically significant increase in the European Production Efficiency Factor (EPEF) for the 10 (p = 0.02) and 15 mg PheCap/kg feed (p = 0.003) treatment doses. No dose dependent adverse effects were found for any of the treatment doses. The No Observed Adverse Effect Level (NOAEL) of PheCap is probably higher than that of the highest weekly averaged daily intake of 36.3 mg/kg BW/day observed in the present study. Conclusions: The inclusion of PheCap in broiler feed at doses relevant for the commercial poultry industry is assumed not have any negative effects on broiler health.

Bat ultrasound analysis has been around for several decades and it is one of the most important tools in studies of bat ecology. Discrimination between species is based on intra-specific features of echolocation calls. Identification of species and genera in audio files can be attempted either manually or through software which performs a fully automated discrimination between species. However, significant overlap in various features (e.g. frequencies of calls) exists between species and even genera. Species ID is therefore often not an absolute conclusion, but rather an opinion or best guess, as opposed to DNA tests or measurements on external characters of captured bats. To make things even worse, the probability of actually observing a bat of a given species in space and time is ignored when performing bat ultrasound analysis. This study introduces Bayesian approximation through a new method we have named Alternative Bayesian Bat Analysis (ABBA). We show, through a simple proof-of-concept example, the importance of adding information about the local composition of the bat community, hence making informed decisions regarding which species is most likely present in audio files. The superior performance of ABBA is also shown through an example using R code. Here, we use simulated data for three Pipistrellus spp., a genus with significant overlap in frequencies, but the code can easily be adapted to other bat species and genera worldwide. ABBA outperformed the non-Bayesian approach for all three species. The rare species in the simulated data set was super-inflated when using the non-Bayesian method. Further the results show, contrarily to common belief, that the frequency dominated by a given species in a data set, depends on the composition of the bat fauna and not just means and SDs reported in the literature. ABBA allows researchers to include all observations in statistical modeling, rather than excluding observations, an approach which can affect the reliability of studies. This study also, to a great extent, explains the poor performance of software attempting automated bat ID. Implementing Bayesian algorithms, and thereby allowing users to interact with the software, should significantly improve their performance.

Accurate abundance estimates are crucial for evidence-based fisheries management. In rivers, drift dive counting and electrofishing are commonly used for quantifying fish abundance. However, the likelihood that fish are detected by these counting methods is affected by a range of factors, with substantial potential implications for the outcomes. Fish behavior and distribution also differs with light intensity, yet diel variation in abundance estimates produced by common enumeration methods has received little attention. Here, we present a comparison of diurnal and nocturnal counts of the landlocked population of Atlantic Salmon Salmo salar, known as "smablank," and Brown Trout Salmo trutta in a Norwegian river. Six drift dive transects and 12 electrofishing sites were surveyed at day and night in early autumn. During drift dives, smablank were exclusively observed at night. Brown Trout were observed by snorkelers both day and night but in significantly higher numbers at night (six times more Brown Trout per 100 m at night versus in the day). Catch per unit effort of backpack electrofishing was significantly higher at night than at daytime for both smablank and Brown Trout older than age 0 (202% and 108% higher, respectively). We argue that differences in drift dive counts were mainly caused by fish hiding in the substrate during the day and being more active at night, resulting in diel differences in detection rate. Further studies are needed to determine whether differences in electrofishing catches were caused by diel fish migrations or higher catchability at night.

Fin whales (Balaenoptera physalus) and humpback whales (Megaptera novaeangliae) are commonly found in the Norwegian Sea during the summer months. Records from around 1995 to 2004 show that their distribution patterns were mainly associated with those of macro-zooplankton. More recent studies conducted from 2009 to 2012 demonstrate marked shifts, with fin whale distribution related to pelagic fish distribution, decreasing densities of humpbacks, and increased densities of toothed whales. During the same period, historically large abundances of pelagic planktivorous fish in the Norwegian Sea were reported. The goals of this study were to examine the summer distribution of fin and humpback whales from 2013 to 2018 and to assess the potential association between distribution and environmental impact factors. Results suggest a pronounced northerly shift in distribution for both species, a feeding hotspot for fin whales at the shelf area between Svalbard and Norway, and one near Bear Island for humpback whales. Fin whale distribution was associated with that of blue whiting (Micromesistius poutassou) and capelin (Mallotus villosus), whereas humpback whale distribution was associated with that of euphausiids (Meganyctiphanes norvegica, Thysanoessa longicaudata, and Thysanoessa inermis), capelin, and herring (Clupea harengus). However, a significant negative spatial correlation was found between whale occurrence and the widely expanding population of northeast Atlantic mackerel (Scomber scombrus). The results of this study suggest that the prey composition of fin and humpback whales in recent years contain a large proportion of fish. The apparent northerly shift in the distribution of these whale species is largely determined by the availability of prey, but it likely is also impacted by direct or indirect interspecific interactions, especially with killer whales (Orcinus orca). Such large-scale pronounced changes in distribution seem to confirm a high degree of plasticity in fin and humpback whale feeding in the Norwegian Sea.

The effect of size-selective predation on prey communities and their traits is well documented, but the relative roles of genetic adaptation and phenotypic plasticity continue to be debated. We looked for evidence of genetic adaption in a population of the water flea Daphnia pulex that faced a novel, introduced predator, Eurasian perch (Perca fluviatilis), selectively preying upon large zooplankton. Theory predicts adaptive changes towards a faster life history. We compared growth, age and length at maturation, egg size, and fecundity of two groups of clones kept in common-garden conditions, 13 clones isolated at around the time of the perch introduction and 14 isolated 3 years after. All animals were photographed daily and observed every third hour to detect maturation and measure the clutch size. Post-introduction clones matured earlier, but this was an indirect response triggered by genetic change in growth: post-introduction clones had faster growth prior to maturation than pre-introduction ones, reaching earlier the size threshold for maturation, but the threshold itself remained unchanged. Post-introduction clones showed also higher clutch size for 2nd and 3rd clutch, and slower growth from maturation (first appearance of eggs) to the moult after the release of the first clutch. Egg size did not differ between the periods. The experiment shows how life-history responses to predation involve multiple interlinked traits and both direct and indirect genetic responses.

Vertebrata lanosa is a small red epiphytic alga growing almost exclusively on Ascophyllum nodosum. It has recently gained attention as a food alga in the North Atlantic. We examined distribution of V. lanosa in relation to environmental factors, by measuring cover of A. nodosum and V. lanosa in sample quadrats at 27 stations in an area in southwestern Norway. The probability of finding high cover (hotspots) of V. lanosa (defined as scores of V. lanosa belonging to the upper 25 % of data) was analysed in relation to height above Chart Datum, wave exposure, cardinal direction, inclination and substratum type. The relationship between amount (cover or volume) of the host alga (A. nodosum) and cover of V. lanosa was also examined. A significant and positive relationship between high cover of V. lanosa and increasing wave exposure was found, which may be attributed to the fact that wave action can cause scrapes and wounds on A. nodosum branches, where spores of V. lanosa have higher chances of successful settlement and survival. The results also showed a significant negative impact of high cover or large volume of A. nodosum on V. lanosa. Finally, the probability of finding high cover of V. lanosa was highest in the middle part of the Ascophyllum zone. The results suggest that the epiphyte and its main host do not have completely overlapping habitat requirements, and that sheltered areas with high biomass of A. nodosum are likely to contain relatively little V. lanosa for harvesting.

To evaluate the safety of the synthetic capsaicin analogue phenylcapsaicin (PheCap; 7-phenylhept-6-yne-acid-hydroxy-3-mathoxylbenzylamide, CAS no 848127-67-3), a 90-day repeated dose oral gavage of 0, 30, 100 or 250 mg/kg body weight (bw)/day toxicity study with a 28-day recovery period was conducted using Wistar rats. Examinations of clinical signs, body and organ weight, haematology, urinalysis, clinical chemistry, food consumption and macroscopic, as well as histopathological tissue examinations were carried out for signs of toxicity. Degenerative, but reversible changes in the liver at 250 mg/kg bw/day, and local irritating effects in the stomach at 100 and 250 mg/kg bw/day were found. These findings were associated with test item-related clinical symptoms, that is, diarrhoea, salivation and moving of bedding material. PheCap did neither cause gene mutations by base pair changes or frame shifts in the genome of the tester stains Salmonella typhimurium TA 98, TA 100, TA 1535, TA 1537 or TA 102 nor induce structural and/or numerical chromosomal damage in human lymphocytes. Therefore, it can be concluded that PheCap is not genotoxic. The No Observed Adverse Effect Level (NOAEL) of PheCap for systemic toxicity is considered to be at 100 mg/kg bw/day which is based on degenerative changes in the liver. Due to irritating effects in the stomach, the NOAEL for local effects was established at 30 mg/kg bw/day.

This study explores the hunting habitat and activity patterns of the soprano pipistrelle Pipistrellus pygmaeus in relation to insect densities and light conditions during summer at 62°N in western Norway. Here, the first soprano pipistrelles emerge at several thousand lux and are common in woodland at more than 1000 lux. In this study, bats tagged with transmitters emerged from their roosts on average one hour before sunset and were airborne for more than five hours each night. During the first hours they always hunted in woodland, but shifted to hunt above the fiord during the night. This shift occurred on average 2 h and 25 min after evening emergence and 1 h and 30 min after sunset. In addition to using radio telemetry, bat contacts over the fiord were counted using ultrasound detectors and car transects. Simultaneously, insects were collected using suction traps and light levels were measured. There was a highly significant effect of light intensity on the number of bats hunting along the fiord. Predictions based on a second order polynomial generalised linear model (GLM) shows that soprano pipistrelles will start to hunt above the fiord when light levels drop below approximately 25 lux. It also suggests a slight reduction of insects as bat numbers increase along the shoreline. The GLM model explains approximately 92% of the variation in the dataset. Ultrasound recordings show that soprano pipistrelles attack far more prey per effort near the shores compared to areas further away. The results found in this study strongly suggest that habitat selection is a trade-off between food energy intake and other factors, e.g. predation risk.

The dominant colour through the intermoult cycle of Carcinus mamas (Linnaeus, 1758) changes from green to orange, then to red. The external developmental stages of the rhizocephalan parasite Sacculina carcini Thompson, 1836 are correlated with this cycle such that the youngest stages predominantly occur when the crabs are green, the intermediate stages when they are orange, and the oldest when they are red. Fouling by the barnacle Balanus crenatus Bruguiere, 1789 increases through this cycle as well, with both sacculinised and unparasitised crabs of orange or red colour being significantly more fouled than green crabs. Sacculinised green crabs with younger external parasite stages are generally least fouled, whereas orange and red crabs with late parasite stages are most fouled, but only female crabs show a statistically significant positive association between Sacculina infection and fouling. For both sexes, time since moulting, indicated by crab colour, is the most important predictor for fouling by B. crenatus.

AbstractHost–parasite systems have been useful in understanding coevolutionary patterns in sympatric species. Based on the exceptional interaction of the long‐lived and highly host‐specific freshwater pearl mussel (FPM; Margaritifera margaritifera) with its much shorter‐lived host fish (Salmo trutta or Salmo salar), we tested the hypotheses that a longer duration of the parasitic phase increases fitness‐related performance of mussels in their subsequent post parasitic phase, and that temperature is the main factor governing the duration of the parasitic phase. We collected juvenile mussels from naturally and artificially infested fish from eight rivers in Norway. Excysted juvenile mussels were maintained separately for each collection day, under similar temperature and food regimes, for up to 56 days. We recorded size at excystment, post excystment growth, and survival as indicators of juvenile fitness in relation to the duration of the parasitic phase. We also recorded the daily average temperatures for the entire excystment period. We observed strong positive relationships between the length of the parasitic phase and the post parasitic growth rate, size at excystment and post parasitic survival. Temperature was identified as an important factor governing excystment, with higher temperatures decreasing the duration of the parasitic phase. Our results indicate that juvenile mussels with the longest parasitic phase have better resources (larger size and better growth rate) to start their benthic developmental phase and therefore to survive their first winter. Consequently, the parasitic phase is crucial in determining subsequent survival. The temperature dependence of this interaction suggests that climate change may affect the sensitive relationship between endangered FPMs and their fish hosts.

This chapter begins with a brief description of zonation in the pelagic and benthic realms, followed by a description of the topographies of coastal and fjord biotopes, the continental shelf and slope, and the deep ocean. These biotopes shape the habitats for bottom associated marine organisms. This is followed by a description of the physical characteristics of the pelagic ecosystem, including circulation of water masses in fjord ecosystems and a description of the light environment in marine waters. The most numerous fish in the pelagic habitat belong to so-called mesopelagic species. The most common mesopelagic organisms in European deep coastal waters and fjords are pearlside (Maurolicus muelleri), northern lanternfish (Benthosema glaciale), the shrimps (Pasiphaea spp. and Sergestes spp.) and krill (Meganyctiphanes norvegica). The chapter further deals with an overview of temperate organisms (benthos and fish) that inhabit the littoral, sublittoral, continental shelf and slope, deep fjords, and the deep sea.

Chapter 2 Planning Marine Field Studies Jennifer Devine, Jennifer DevineSearch for more papers by this authorKeno Ferter, Keno FerterSearch for more papers by this authorHenrik Glenner, Henrik GlennerSearch for more papers by this authorJon Thomassen Hestetun, Jon Thomassen HestetunSearch for more papers by this authorKnut Helge Jensen, Knut Helge JensenSearch for more papers by this authorLeif Nøttestad, Leif NøttestadSearch for more papers by this authorMichael Pennington, Michael PenningtonSearch for more papers by this authorDavid John Rees, David John ReesSearch for more papers by this authorAnne Gro Vea Salvanes, Anne Gro Vea SalvanesSearch for more papers by this authorKjersti Sjøtun, Kjersti SjøtunSearch for more papers by this authorArved Staby, Arved StabySearch for more papers by this author Jennifer Devine, Jennifer DevineSearch for more papers by this authorKeno Ferter, Keno FerterSearch for more papers by this authorHenrik Glenner, Henrik GlennerSearch for more papers by this authorJon Thomassen Hestetun, Jon Thomassen HestetunSearch for more papers by this authorKnut Helge Jensen, Knut Helge JensenSearch for more papers by this authorLeif Nøttestad, Leif NøttestadSearch for more papers by this authorMichael Pennington, Michael PenningtonSearch for more papers by this authorDavid John Rees, David John ReesSearch for more papers by this authorAnne Gro Vea Salvanes, Anne Gro Vea SalvanesSearch for more papers by this authorKjersti Sjøtun, Kjersti SjøtunSearch for more papers by this authorArved Staby, Arved StabySearch for more papers by this author Book Editor(s):Anne Gro Vea Salvanes, Anne Gro Vea Salvanes Department of Biology, University of Bergen, Bergen, NorwaySearch for more papers by this authorJennifer Devine, Jennifer Devine Institute of Marine Research (IMR), Bergen, NorwaySearch for more papers by this authorKnut Helge Jensen, Knut Helge Jensen Department of Biology, University of Bergen, Bergen, NorwaySearch for more papers by this authorJon Thomassen Hestetun, Jon Thomassen Hestetun Department of Biology, University of Bergen, Bergen, NorwaySearch for more papers by this authorKjersti Sjøtun, Kjersti Sjøtun Department of Biology, University of Bergen, Bergen, NorwaySearch for more papers by this authorHenrik Glenner, Henrik Glenner Department of Biology, University of Bergen, Bergen, NorwaySearch for more papers by this author First published: 01 December 2017 https://doi.org/10.1002/9781119184362.ch2 AboutPDFPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShareShare a linkShare onFacebookTwitterLinked InRedditWechat Summary This chapter presents various ways to design a scientific survey for marine field studies, including a description of the most used designs. This is followed by descriptions of some currently employed survey designs for littoral and benthos field studies: an oceanic survey to estimate the abundance of mackerel; a bottom trawl survey to monitor demersal fish populations; a hydroacoustic survey to study the diel vertical migration of mesopelagic organisms, and lastly, a survey design to study barotrauma in physoclistous fish species. The design of a survey can influence the outcomes of the analysis implementing a design that will allow for answering the question without bias is crucial. There are two standard survey designs for field studies. One common design is a stratified random survey. The other common survey design for field studies is a systematic survey. An important aspect for designing a field survey is to determine how and how much to sample at each station. Marine Ecological Field Methods: A Guide for Marine Biologists and Fisheries Scientists RelatedInformation

We present a life-history model based on the assumptions that juvenile survival follows a negative exponential function and that fecundity gain increases linearly with time to maturity. This model predicts that the optimal fitness is achieved when survival at maturity is 0.368 (e(-1)). Survival at the time of maturity is therefore an invariant. We tested this prediction by using published data from infection experiments with mammalian nematodes, where both the initial number of juveniles colonizing a habitat (host) and the numbers surviving at the time of maturation were known. We found that the mean survival at maturity, both across and within species, was remarkably close to our predicted mean. As a control, we also looked at studies where the parasite species was adapted to a host species other than the one used in the reported experiment. In these experiments the mean survival at maturity differed from what our model predicted. Maturation at a fixed survival probability therefore appears as an adaptive trait evolved in a predictable environment, in this case, a host species. Our result further suggests that measures designed to increase juvenile parasite mortality, such as drugs or vaccines, will select for faster developmental rates.

The high loss of newly released hatchery-reared European lobster (Homarus gammarus) juveniles for stock enhancement is believed to be the result of maladaptive anti-predator behaviour connected to deprived stimuli in the hatchery environment. Our objective was to learn if an enriched hatchery environment enhances shelter-seeking behaviour and survival. In the “naïve” treatment, the juveniles were raised in single compartments without substrate and shelter whereas juveniles in the “exposed” treatment experienced substrate, shelter and interactions with conspecifics. Three experiments with increasing complexity were conducted. Few differences in shelter-seeking behaviour were found between treatments when one naïve or one exposed juvenile were observed alone. When observing interactions between one naïve and one exposed juvenile competing for shelter, naïve juveniles more often initiated the first aggressive encounter. The third experiment was set up to simulate a release for stock enhancement. Naïve and exposed juveniles were introduced to a semi-natural environment including substrate, a limited number of shelters and interactions with conspecifics. Shelter occupancy was recorded three times during a period of 35 days. Exposed juveniles occupied more shelters, grew larger and had higher survival compared with naïve juveniles. Our results demonstrate that experience of environmental complexity and social interactions increase shelter-seeking ability and survival in hatchery reared lobster juveniles.

Murchison Bay in the Northern part of Lake Victoria has for decades received a daily wastewater load of 0.2% of its volume from Kampala City, through the Nakivubo channel. In spite of this, the Water Treatment Works abstracts raw water from this bay and has been able to produce drinking water of sufficient quality for the capital. This study monitored various physical chemical components within the bay during 2000-2003 to understand the processes responsible for the acceptable quality of raw water. Four sampling stations were located along a transect from the channel mouth towards the open lake.Results: showed that the wastewater did not accumulate in the bay, instead was already strongly diluted 2.5 km from the channel mouth. This caused an abrupt reduction in conductivity and the concentrations of the nutrients total phosphorus (Tot-P), orthophosphate (PO4-P) and total nitrogen (Tot-N).Inshore-offshore exchange of water was mediated by flows from daily and sub-daily water level fluctuations and wind-driven currents. As a daily average, 2% of the Murchison Bay flowed in and out and the incoming wastewater was diluted 9.7 times.During the dry season from June to August (D2), when the weather was influenced by the south-east monsoon, the thermal stratification in the main lake disappeared and cooler and deoxygenated water from deeper depths entered the bay influencing its water quality.The daily flushing of water in and out of the bay due to water level variation was identified as the main factor diluting the bay water. (C) 2015 Elsevier GmbH. All rights reserved.

Male investment in testes and sperm duct gland in the polygamous nest breeding two-spotted goby Gobiusculus flavescens (Fabricius) was investigated in relation to time in reproductive season and individual physical parameters. This small teleost fish is most likely the most abundant species found along the rocky shores of the North East Atlantic. The two-spotted goby has a single reproductive season, during which nest-caring males can raise several clutches of offspring. According to the literature the males are on average larger than the females. Here we report for the first time a population showing a reversal of this trend, with males on average being smaller than females, a difference likely caused by a large proportion of small males. Early in the breeding season these small males have typical sneaker characters, with relatively large testes and small seminal duct glands compared to the larger dominant territorial males. The presence of these two alternative male reproductive tactics is confirmed by histological studies, which shows the presence of sperm in the sperm duct glands (SDG) of smaller males, but not in the SDG of intermediate and larger males. To our knowledge, males with typical sneaker characters have not been reported in earlier studied populations of two-spotted goby. Interestingly we found that testes investment declined significantly over the course of the breeding season, and that this reduction was significantly more pronounced in small compared to the large males. Further, a significant increase in seminal duct gland (SDG) mass was observed for the smaller males over the breeding season. We propose that this indicates a possible shift in mating tactic by smaller males from a parasitic to a nest-holding tactic over the course of the breeding season. Thus, the observed size dependent plasticity in investment in SDG over time suggests that the reproductive tactic of G. flavescens is conditional, and possibly influenced by mate availability and male--male competition.

Pelagic fish typically swim in shoals, but a full understanding of behaviour, including individual spatiotemporal dynamics and the relationships between individuals and the social unit, can only be achieved through studies of individual fish. We studied horizontal and vertical movement of tagged individual Atlantic herring (Clupea harengus L.) inside a semi-enclosed ecosystem throughout the dynamic spawning season. Twenty-four fish were successfully tagged with acoustic transmitters and followed for up to 62 d (average 28 d) using a network of ultrasonic receivers. Herring samples from gillnets provided information about gonadal maturity. During pre-spawning, all individuals remained within the range of a single receiver, but with marked and predictable diel vertical migrations (DVMs). As maturation progressed, the number of herring on the spawning grounds gradually increased, while swimming depth and DVMs gradually decreased. However, the daily vertical distance moved by single individuals increased markedly as spawning approached, and the individual variability in both horizontal and vertical positioning also increased over time. During the period assumed to include spawning, individuals moved more frequently between the receivers, with dives towards the bottom presumed to represent spawning events. The results indicate a development from low variability in individual positioning and strong school coherence before spawning, to high variability during spawning that could reflect individual states of maturation. The study demonstrates that novel acoustic tagging technology opens up the possibility of investigating the dynamic trade-offs between collective behaviour and individualism in schooling pelagic fish.