Tagged Fish Research Articles

Winter Habitat Selection and Efficacy of Telemetry to Aid Grass Carp Removal Efforts in a Large Reservoir

AbstractGrass Carp Ctenopharyngodon idella were introduced in North America to control aquatic vegetation in small, closed systems. However, when they escape into larger systems in which they can reproduce, they have the potential to cause significant declines and alterations in aquatic vegetation communities. These alterations can in turn affect native species that are dependent on aquatic vegetation. Increased captures and observations of spawning have elevated concerns about Grass Carp establishment in new locations, with particular concern for establishment in Lake Erie and its tributaries. Recent efforts using telemetered fish that co‐locate with wild conspecifics, sometimes in aggregations that are susceptible to harvest, have been used successfully to control invasive Common Carp Cyprinus carpio populations. If Grass Carp aggregate in winter similarly to Common Carp, they might be susceptible to similar control or harvest methods. During the winters (December–March) of 2017–2019, we tracked 86 Grass Carp tagged with acoustic transmitters in Truman Reservoir, Missouri, to evaluate winter habitat selection and to determine the effectiveness of using tagged fish in locating and removing wild fish by comparing harvest at locations of tagged fish to harvest at control sites that we believed were suitable Grass Carp habitat. Discrete‐choice models showed that Grass Carp exhibited strong selection for shallow water, as 75% of locations were in littoral habitats with depths of 3 m or less. On average, we harvested more fish at sites where tagged fish were located (3.6 fish/attempt) than at control sites (1.2 fish/attempt). Full guts in individuals that were harvested may indicate that fish were using shallow‐water habitats to feed. Our results suggested that Grass Carp did not usually form large winter aggregations, and although targeting locations with tagged fish slightly increased harvest success compared to efforts without them, efforts to reduce populations via harvest may be difficult in large systems when fish are widely dispersed.

Laboratory and Field Experimental Validation of Two Different Predation Sensors for Instrumenting Acoustic Transmitters in Fisheries Research

We validated the performance of two types of predation sensors on acoustic telemetry transmitters in a combined field and laboratory study design using juvenile Atlantic Salmon Salmo salar and a predator large Brown Trout Salmo trutta. One tag model was outfitted with an acid‐sensitive predation sensor, and the other was equipped with a tilt‐based orientation sensor. We found similar response times for the two tag types to identify a predation event (time between known ingestion of a tagged fish and triggering of the predation sensor). However, the orientation sensor model was more accurate in laboratory trials, correctly identifying 100% of events in which predators were fed the tagged fish, whereas correct identification of predation events was 50% for the acid‐sensitive sensor in similar trials. The acid‐sensitive tags were smaller (0.65 g in air), and all 10 were eventually expelled by predators in the laboratory (2–22 d after tag ingestion). By contrast, only two of five tags with orientation sensors (1.4 g in air) were expelled in a similar period (13 and 16 d after tag ingestion). Both tags had distinct benefits: acid‐sensitive sensor tags were very small, and orientation sensor tags were seemingly more accurate and transmitted raw orientation data to receivers for postprocessing.

Identifying juvenile and sub-adult movements to inform recovery strategies for a high value fishery—European bass (Dicentrarchus labrax)

Abstract The European bass (Dicentrarchus labrax) support high value commercial and recreational fisheries, however the Spawning Stock Biomass (SSB) of the northern Atlantic stock (ICES divisions 4.b–c, 7.a, and 7.d–h) has rapidly declined to an unsustainable level. The decline in SSB has been attributed to high fishing pressure combined with poor recruitment. By tracking juvenile fish their spatial ecology can be identified, and appropriate fisheries management policies designed to boost recruitment can be implemented. Using acoustic telemetry 146 sub-adult European bass (25.2–60 cm fork length) were tracked for up to 370 d across three sites in the southwest of the UK. Tagged fish were detected 2 724 548 times (Range: 166–106 393 detections per fish). Linear modelling estimated tagged fish were resident within 2.4–20.1 km of the site where they were first caught for 42.9–75.5% of the year. Some fish were however resident throughout summer and winter. Individual fish were also tracked moving up to 317 km to other coastal sites, 81% of which returned to their original capture site. Fisheries management should account for the high site fidelity displayed by juveniles and sub-adults of this species and coastal nursery sites should be considered essential habitat.

Relationships between maturational status and migration behavior of homing chum salmon Oncorhynchus keta in inner bays of the Sanriku coast

The correlations among gonad maturity and various homing behaviors of chum salmon, Oncorhynchus keta, were evaluated using acoustic tracking of tagged fish in Otsuchi Bay, Japan. There was a negative correlation between the time duration from release of tagged fish until river entry and the plasma 17α, 20β-dihydroxy-4-pregnen-3-one (DHP) levels, an indicator of final maturation. Females with high DHP entered the rivers soon after the release, whereas females with low DHP (<10 ng/ml) took a few days to more than one week until river entry. Similar correlation was also found in males. A pattern of river entry correlated with maturational conditions was also observed in fish entering the rivers of neighboring bays. DHP concentrations of fish caught in the rivers were consistently higher. On the other hand, more than half of released salmon departed from the bay regardless of their plasma DHP level, suggesting that maturational status does not force homing adults to enter the most available nearest rivers. Fish entering the rivers experienced ambient temperatures less than 8 °C, which is approximately 5 °C lower than that of the bay. These results indicate that homing salmon hold their position in the bay until just before spawning, which may be attributable to low temperature avoidance. This characteristic type of river entry may be suitable to geographical features and thermal regimes of this region.

Computer vision based individual fish identification using skin dot pattern

Precision fish farming is an emerging concept in aquaculture research and industry, which combines new technologies and data processing methods to enable data-based decision making in fish farming. The concept is based on the automated monitoring of fish, infrastructure, and the environment ideally by contactless methods. The identification of individual fish of the same species within the cultivated group is critical for individualized treatment, biomass estimation and fish state determination. A few studies have shown that fish body patterns can be used for individual identification, but no system for the automation of this exists. We introduced a methodology for fully automatic Atlantic salmon (Salmo salar) individual identification according to the dot patterns on the skin. The method was tested for 328 individuals, with identification accuracy of 100%. We also studied the long-term stability of the patterns (aging) for individual identification over a period of 6 months. The identification accuracy was 100% for 30 fish (out of water images). The methodology can be adapted to any fish species with dot skin patterns. We proved that the methodology can be used as a non-invasive substitute for invasive fish tagging. The non-invasive fish identification opens new posiblities to maintain the fish individually and not as a fish school which is impossible with current invasive fish tagging.

A Novel Miniaturized Biosensor for Monitoring Atlantic Salmon Swimming Activity and Respiratory Frequency.

Simple SummaryGood fish welfare is one of the prerequisites for sustainable aquaculture. Knowing how fish respond to the production conditions would allow us to better understand their biology and to further optimize production. The new miniaturized biosensor AEFishBIT was successfully used to monitor individual physical activity and respiratory frequency of two Mediterranean farmed fish species (gilthead sea bream and European sea bass). In this study, we aimed to test the use of AEFishBIT to monitor the performance of Atlantic salmon under experimental conditions. An adapted tagging procedure for salmon was developed and used to record salmon responses to handling and changing light conditions. AEFishBIT data showed a stabilization of swimming activity 8 h after handling and tagging with changes in activity or activity and respiratory quotient after changes in light intensity regimes. The results of this study supported the use of AEFishBIT to generate new behavior insights in Atlantic salmon culture.The advanced development of sensor technologies has led to the emergence of fish biosensors that are currently used for research and commercial purposes. AEFishBIT is a miniaturized biosensor attached to fish operculum that measures physical activity and respiration frequencies. In this study, we determined the effect of the tagging method and evaluated the use of this biosensor to monitor post-smolt Atlantic salmon in a tank-based system. The use of piercing fish tag had a negative impact on the gills and operculum, unlike the identical protocols used in gilthead sea bream and European sea bass. In contrast, a surgical thread did not show any apparent tissue damage. Two data recording schedules were considered to monitor immediate early reaction to fish handling and light regime changes (records every 15 min over 2 days) or adaptation to new light conditions (records every 30 min over 4 days). Data showed stabilization of physical activity 8 h post-tagging, with different steady states for the activity/respiratory ratio after changes in light intensity that reflected a different time course adaptation to new light conditions. High correlations were observed between AEFishBIT and video recording data. These findings supported the use of AEFishBIT as a promising tool for smart sensing of Atlantic salmon.

Are tag-based integrated stock assessments robust to IUU fishing?

Integrated stock assessments depend on reliable catch and observational data to produce unbiased estimates of fish stock biomass and productivity. However, biases in catch data due to unreported catch are common among many of the world’s fisheries, especially those that are high value and therefore more vulnerable to illegal fishing. Some of these fisheries rely on tag-recapture data to support the estimation of biomass in integrated assessments and set precautionary catch limits intended to safeguard the fish stocks from overexploitation. Tag-recapture data is generally considered to be a more powerful indicator of stock abundance than survey data if the underlying assumptions are met. The effect of unreported catches that include tagged fish on biomass estimates in tag-based integrated assessments is unclear. We used a simulation analysis to determine the impact of under-reported catch on a hypothetical Patagonian toothfish (Dissostichus eleginoides) stock. Several catch scenarios are presented that cover different magnitudes and trend types of under-reported catch. We used the CASAL model (commonly employed to assess toothfish stocks) as both the operating model and the estimation model to evaluate how the various scenarios affected estimation performance of biomass depletion. Biomass depletion was increasingly underestimated as the magnitude of under-reporting increased, regardless of trend in catch. When unreported catch exceeds twice the amount reported combined with unreported tag returns, the estimation model will fail to detect biomass has been depleted below a target reference point of 50 % within 20 years of fishing. The lack of detection will falsely indicate current catch limits are sustainable when in reality they are not. Importantly, these estimates remained largely unchanged among different trends in under-reported catch. For assessments reliant on tag-recapture data, this suggests that it is more critical to estimate the overall quantity of unreported catch and the number of unreported tagged fish than the trend.

The consequences of dam passage for downstream-migrating American eel in the Penobscot River, Maine

American eel (Anguilla rostrata) often pass hydropower dams during adult spawning migrations. We conducted a 4-year acoustic telemetry study that characterized passage risks through two dams (West Enfield and Milford) in the Penobscot River, Maine, USA. We released tagged fish (n = 355) at two sites, estimated survival and delay under variable river conditions, and compared performance among dammed and free-flowing river sections. Survival rates (standardized per river kilometre, rkm) were lower at West Enfield (Φrkm = 0.984 ± 0.006 SE) and Milford (Φrkm = 0.966 ± 0.007 SE) compared with undammed River sections (Φrkm = 0.998 ± 0.0003 SE). Cumulative mortality was 8.7% (4.4 km) and 14.2% (5.5 km) through dammed sections and 8.7% throughout the rest of the river (58.1 km). Fish that already passed an upstream dam incurred higher downstream mortality compared with individuals without passage experience. Additionally, fish endured long delays at dams, and &gt;10% of fish were delayed &gt;24 h. Low flows exacerbated the risk of mortality and delay. These results offer evidence for direct, latent, and sublethal consequences of dam passage for migrating eels.

A Review of Marking and Tagging Methods for Blue Catfish, Channel Catfish, and Flathead Catfish

AbstractCatfishes (Ictaluridae) are among North America’s most important ichthyofauna for human consumption and recreation. As such, research on Blue Catfish Ictalurus furcatus, Channel Catfish I. punctatus, and Flathead Catfish Pylodictis olivaris has been abundant in historic and contemporary literature. A common technique for studying catfish involves marking or tagging fish to understand behavior, sampling efficiency, and population dynamics. Marking and tagging methods used in these studies may be divided into eight primary types, including fin clips, strap tags, anchor tags, transbody tags, injectable tags, skin alterations, origin markers, and telemetry. Each of these methods is appropriate for specific objectives and characterized by varying retention rates and data resolution (i.e., batch or individual identification) that warrant consideration when designing projects. For example, fin clips may be most appropriate as a short‐term mark requiring batch identification (e.g., stocking evaluation), whereas telemetry might be most appropriate as a long‐term tag requiring individual identification (e.g., habitat selection). This review summarizes marking and tagging methods used for evaluation of Blue, Channel, and Flathead catfish and synthesizes results using examples from previously conducted catfish research. Further discussion is included on information gaps, emerging trends, and guidance for scientists planning and conducting studies that require marking of catfish.

Evaluation of Visual Implant Elastomer, PIT, and p‐Chip Tagging Methods in a Small‐Bodied Minnow Species

AbstractReliable fish tagging methods are needed to conduct studies (e.g., movement, habitat, abundance) that inform conservation and management decisions; however, dependable tagging approaches are lacking for many small‐bodied fishes. Therefore, our study objective was to determine survival, tag retention (visible implant elastomer [VIE], PIT, or light‐activated microtransponder [“p‐Chip”]) and tagging effects on short‐term growth of the federally threatened Arkansas River Shiner Notropis girardi. We also examined the use of anesthesia to reduce fish mortality (i.e., reduce handling time) and improve tagging efficiency. Fish tagged with p‐Chips had the highest survival (87%), whereas VIE‐tagged fish had the second highest survival (67%). Visible implant elastomer tags were retained in our fish 88% of the time, and retention was also high using p‐Chips (72%). Location of the VIE tag did not significantly affect survival or retention rates. Survival of PIT‐tagged fish significantly increased from 53% to 83% when handling time was reduced; however, tag retention was relatively low in both cases (50% and 45%, respectively). The majority of tagged fish across experiments (83–100%) gained weight regardless of tag type. If the research or management goal is to tag Arkansas River Shiner or similar species with individual identification, p‐Chips appear to be an appropriate tag. Particularly if cost is limiting or higher tag retention is needed, VIE tags would also be appropriate for batch tagging (i.e., no individual identification). Additional studies to broaden application of tagging to other small‐bodied species would be beneficial.

Habitat use and activity patterns of female Deacon Rockfish (Sebastes diaconus) at seasonal scales and in response to episodic hypoxia

We combined a high-resolution acoustic telemetry array with presence/absence receivers to conduct a preliminary study of the seasonal movements, activity patterns, and habitat associations of the newly described Deacon Rockfish (Sebastes diaconus). Eleven mature female Deacon Rockfish were tagged and monitored during an 11-month period, at a nearshore rocky reef off Seal Rock, Oregon, USA, an area of recurring seasonal hypoxia (defined as dissolved oxygen concentration [DO] < 2 mg l−1). Two tags were detected leaving the study area by day 35, indicating predation or emigration. Three tags became inactive within the array, indicating tag loss or fish death. Six “resident” fish inhabited the array for 246–326 days. Resident fish exhibited high site fidelity, small home ranges (mean 95% KDE = 4907 m2), and consistent activity patterns for the duration of the summertime high-resolution array (5 months), except during seasonal hypoxia. Resident fish were strongly diurnal in summer, with high levels of daytime activity above the bottom in relatively rugose habitat, followed by nighttime rest periods in deeper, less rugose habitat. During summertime hypoxia, resident fish exhibited less daytime activity during daytime hours with no rest periods at night, inhabited shallower water depths, and moved well away from their core activity areas on long, erratic forays. During the winter, diel patterns were less evident with higher activity levels at night (than in the summer) and lower activity levels in the day (than in the summer). We propose that some Deacon Rockfish continuously inhabit nearshore reefs throughout the year, but that daily/seasonal movement patterns, seasonally occurring hypoxia, and prey preferences for planktonic organisms influence relocation.

Exposure Time of Wild, Juvenile Sockeye Salmon to Open‐Net‐Pen Atlantic Salmon Farms in British Columbia, Canada

AbstractThe role that open‐net‐pen farms for Atlantic Salmon Salmo salar play in the global decline of stocks of wild salmonids (Salmo spp. and Oncorhynchus spp.) is contentious; Canada’s west coast is no exception. We identified the proportion of acoustic‐tagged juvenile Sockeye Salmon Oncorhynchus nerka migrating through the main migration routes of the Discovery Islands region of British Columbia and measured both residence time in a major waterway hosting several Atlantic Salmon farms and exposure times to individual farms. One‐third of tagged fish migrated through this channel, with median residence times of 32.6 h in 2017 and 46.0 h in 2018. The median time near individual farms was 4.4 min in 2017 when farms were fallow and 10.9 min in 2018 when farms were stocked. The increase in 2018 was probably not caused by farm activity because the proportion of total time spent in the channel was the same across years. Sockeye Salmon used all major migration pathways, but the lack of farms and rapid migration speeds in the westernmost passage offers the lowest potential exposure to fish farms. These are the first individual‐level data available to inform assessments of the transmission risk of infectious agents from farms to wild salmonids.

Survival and Movement Patterns of Rainbow Trout Stocked in a Groundwater‐Influenced Warmwater Stream

AbstractStocking Rainbow Trout Oncorhynchus mykiss to create additional angling opportunities is common; however, the spatial and temporal dynamics of such stocking practices are unclear in groundwater‐influenced, warmwater streams. Our objectives were to determine Rainbow Trout dispersal from a stocking location on Spavinaw Creek, Oklahoma and to quantify apparent survival of two cohorts of Rainbow Trout stocked in November 2018 and February 2019. Rainbow Trout were PIT‐tagged prior to autumn (N = 495) and winter (N = 605) stocking and located poststocking using both an active floating array and two passive fixed arrays. We actively tracked a 6‐km extent every 2–3 weeks poststocking and found that PIT‐tagged Rainbow Trout dispersal ranged from 0 to 4 km with ~90% of detected tagged fish remaining within 1 km of the stocking location. Directional movement by stocked Rainbow Trout was evident with upstream movements related to increases in daily water discharge and downstream movements related to decreases in daily discharge. Estimated apparent weekly survival of Rainbow Trout was lowest during the first 2 weeks poststocking (91% and 75% for autumn and spring cohorts, respectively). Apparent weekly survival rates for both autumn and spring stocked fish increased through winter and spring when maximum water temperatures were below 25℃, reaching survival rates of 99% by the end of spring. Rainbow Trout persisted in Spavinaw Creek throughout the summer; however, the weekly apparent survival rate declined for both cohorts (93%) when maximum daily water temperatures exceeded 25°C. Our results can be used to guide stocking decisions in similar warmwater streams and suggest that Rainbow Trout persist through spring and summer poststocking under the conditions encountered during our study.

Variation in Black Bass Angler Characteristics by Stream Size and Accessibility in Oklahoma’s Ozark Highland Streams

AbstractFishing in streams and rivers is a popular outdoor recreation activity in eastern Oklahoma, where most anglers target black bass (Micropterus) species. Since the early 1990s, when the last assessment of black bass fishing in the region was conducted, broadscale factors such as harvesting behavior, state fishery regulations, and bass population dynamics have changed. In 2018, we conducted creel and fish tagging surveys in three tributaries of Lake Tenkiller (Caney Creek, Baron Fork, and Illinois River) that differed in size and accessibility to provide current estimates of catch, harvest, and effort directed toward black bass. We then related these estimates to angler socioeconomic characteristics. The amount of angler effort was concomitant with stream size and accessibility, being greatest in the largest stream with the most access (Illinois River). However, catch rates were highest in the medium‐sized stream (Baron Fork). Harvest rates and exploitation were near zero in all systems. Anglers fishing Caney Creek, the smallest and least accessible stream, were nearly all local, coming from zip codes ~42 km away, with low median household incomes compared to anglers at the other streams who came from a broader array of more distant zip codes and had higher median household incomes. Anglers fishing the smallest stream were also more interested in harvesting fish and having higher creel limits than anglers at the other two systems. In the Oklahoma Ozark Highlands, stream size and accessibility appear to be a significant factor in angler demographics, potentially necessitating different management strategies.

Tag use to monitor fish behaviour in aquaculture: a review of benefits, problems and solutions

AbstractA variety of tagging techniques are now available to monitor fish behaviour, physiology and their environmental experience. Tagging is frequently used in aquaculture research to monitor free‐swimming individuals within farmed populations. However, for information gathered from tagged fish to be representative of farmed populations, tagging must not fundamentally affect fish behaviour, physiology or survival. Here, we systematically review studies that used tags to monitor farmed fish behaviour and test factors that affect tag retrieval and tag‐related mortality. Most studies using tags assessed movement and swimming behaviour in salmonids, predominantly in Europe and North America. Mortality of tagged fish was 10 times higher in sea‐cages (mean = 25%, range = 0–61.5%,n = 22 studies) than in tanks (mean = 2.5%, range = 0–17%,n = 23 studies), while mortality of tagged fish in sea‐cages was markedly higher in longer trials (from 4% in single day trials to 36% after 100 days). Higher‐than‐usual mortality rates among tagged fish, together with largely unknown sublethal effects on behaviour, should caution against using tagging studies to make decisions related to farm management. Moreover, key metrics such as mortality rates of tagged and untagged fish or evidence of sublethal effects are often unreported. We make several recommendations to improve future tagging studies and increase transparency in reporting. A greater insight into the causes of tagged fish mortality in sea‐cages is required to secure animal welfare and data validity in studies that use tags to assess fish behaviour in aquaculture.

An acoustic sensor transmitter for in situ assessment of water quality and fish behaviour during chemical treatment of a parasite-infected river system: tag design and practical use

BackgroundBehaviour of potential host fish during chemical treatment against the ectoparasite Gyrodactylus salaris is a vital factor in designing treatment strategies, evaluating risk factors and establishing insights into previously failed treatments. The effectiveness of any chemical treatment may be compromised if fish either are forced to, or seek out actively, areas of the river where the water quality is less affected by the chemicals. The aim of this study was to develop and apply an acoustic fish tag for fish localization with sensors for in situ measurement of water conductivity and temperature to investigate fish behaviour before, during and after an aluminium (Al) treatment. The sensor tag allowed discrimination between water qualities, and thereby quantification of exposure to treatment water.FindingsAdult Atlantic salmon and anadromous brown trout from river Lærdalselva were tagged with external conductivity transmitters and followed daily by a network of passive receivers and by manual tracking 1 week ahead of treatment, during a 2-week aluminium (Al) treatment period and one week after an Al treatment. The results show no avoidance behaviour related to the Al treatment and most of the fish exhibited a behaviour during the treatment that did not differ significantly from the behaviour observed before or after the treatment. Data collected from the tags showed that the fish experienced increased conductivity during Al administration, suggesting successful exposure to treatment water. The tag gave verifiable environmental information and functioned well in the turbulent and acoustically demanding river environment, albeit with variable detection range.ConclusionsThe conductivity and temperature tag provided novel data on fish behaviour and exposure during the Al treatment period. Results show that fish exhibit normal behaviour during this period and no avoidance response can be detected in the collected data.

Residence and movement patterns of the marbled flounder Pseudopleuronectes yokohamae around a spawning ground in southern Suo Nada, Seto Inland Sea, Japan

The residence and movement patterns of the marbled flounder Pseudopleuronectes yokohamae were investigated around a spawning ground located off the coast of Nagasaki point, southern Suo Nada, Seto Inland Sea, Japan. Twenty marbled flounder (9 females and 11 males) tagged with ultrasonic transmitters were released on November 29, 2017, before the peak spawning season (peak spawning season: mid–late December), and their distributions were recorded by 15 acoustic receivers until January 21, 2018. Eighteen fish roamed around in the study site or disappeared from the study site but appeared again. The 18 fish then emigrated from the study site by mid-December. The remaining two (1 female and 1 male) of the 20 tagged fish resided until mid-January and continuously roamed around areas of silt–clay to very coarse sand bottom sediments both day and night during the peak spawning season. Movement patterns of marbled flounder may be related to spawning site selection or reproductive behaviors. The fish that emigrated may have roamed around the study site or surrounding areas in order to judge whether to spawn there, but most of them may not have in the study site. In contrast, the remaining two fish may have reproduced within the study site.

Genetic diversity and structure of the commercially important native fish pacu (Piaractus mesopotamicus) from cultured and wild fish populations: relevance for broodstock management

Pacu (Piaractus mesopotamicus) is one of the most important Neotropical freshwater fish species produced by aquaculture in South America. This study is the first attempt to inquire about aquaculture stocks in Argentina regarding genetic diversity and structure. Neither genetic characterization nor pedigree records are available for pacu stocks in farms in Argentina. The presence of hybrids in both natural environment (Lower Paraná River) and farms has not been evaluated yet at the southern region of pacu distribution. Genetic characterization of pacu broodstocks, corresponding to 8 farms, and wild individuals from four areas at Lower Paraná River was performed. Pacu hybrids were not detected neither in wild nor in farm stocks analyzed. In general, similar levels of genetic diversity were observed between cultured and wild fish populations. Global genetic differentiation (Fst = 0.055) indicated a low level of structure and AMOVA showed that genetic variation was mostly within populations. Reduced contemporary effective population size (Ne) was observed, and probably reflects the bottleneck by founder effect in farmed fish populations. Moreover, kinship analysis showed that in fish farms, on average, 43.00% of the individuals were genetically related, whereas in wild population it was 36.40%. We recommend that broodstock management practices, such as using large Ne, single pair mating, precise records, and tagging of brood fish, should be implemented to avoid unintentional mismanagement.

Editorial

i DOI: https://doi.org/10.3318/BIOE.2021.05 Biology and Environment: Proceedings of the Royal Irish Academy,Vol. 121, No. 1, i–ii (2021). © Royal Irish Academy Cite as follows: Osborne, B. 2021 Editorial / In this issue. Biology and Environment: Proceedings of the Royal Irish Academy 2021. DOI: 10.3318/ BIOE.2021.05 EDITORIAL Bruce Osborne Over one year ago the first case of COVID-19 was recorded in Ireland, but I wonder who remembers the actual date?* Also, does anyone remember all the things we thought we knew about COVID19 and how it should be tackled that turned out, in the end, to be either false or at best equivocal? It will only affect the vulnerable; travel is not important for the transmission of the disease; masks do not work; children can act as vectors, etc. I could go on, but I think you get the picture.To the non-cognoscenti this may seem very strange, but scientific opinions can often differ dramatically, even amongst the so-called experts, only reaching some consensus when there is strong supporting evidence for a particular viewpoint. Unfortunately, this is the way that science works.Of course,several (arguably avoidable) mistakes were made but even now, more than one year after the first recorded case, there are still differing views about how we should proceed or should have proceeded.Thankfully , there now seems to be light at the end of the tunnel, but if you asked me one year ago whether we would still be impacted by this virus in 2021 to the extent that we are I, like many other people, I think, would have answered with a resounding ‘no’! During this last year we have experienced several false dawns and, borrowing another, slightly modified and well-worn cliché, we should not be over-confident that we are out of the woods yet! Despite the impacts of COVID-19 I can report another successful year for Biology and Environment, with the publication of three issues, including a special issue based on a selection of papers presented at Ireland’s first National Biodiversity Conference in 2019.We received approximately one hundred submissions in the last year (with a rejection rate >40%), and many of the papers that were finally accepted underwent significant revisions before they were deemed ready for publication. Encouragingly submissions were received from fourteen countries and covered a diverse range of biological and environmental topics;we hope to build on this and to further internationalise the journal. I can also report that we already have a significant portfolio of papers that are being processed for the next two issues of 2021. Finally, I would like to give my annual thanks to both Jonathan Dykes andTrevor Mullins for their invaluable contributions to the production of Biology and Environment in what has turned out to be very challenging times. *29 February 2020 Lake-dwelling brown trout Lake trout populations support an important recreational fishing industry in Ireland, but information on their behaviour and conservation status—including the extent to which they are exploited by anglers—is lacking. Kennedy et al., in this issue, used acoustic telemetry to track several tagged adult brown trout in Lough Erne, Co. Fermanagh. Although the study was complicated by the shedding of tags and the reduced survival of tagged fish, the authors estimated survival rates of 40–70%. Survival was greatest with the larger adults and most of those were found in the northern deeper part of the lake where there was a higher rate of zooplankton productivity. Rather surprisingly, given the size of Lough Erne and the small number of tagged fish used, a significant proportion were captured by anglers, giving a high (>11%) exploitation rate.Whilst several fish entered feeder tributaries to spawn before returning to the lake, this was often short lived, probably due to the high risk of predation in these relatively narrow and shallow streams. Unusually, several tagged fish overwintered in the lake and spawning was presumably associated with suitable gavel habitats where they could lay their eggs. Importantly >40% of the fish that spawned outside the lake did so in one single tributary probably because it contains habitats that are...

Residential movements of top predators in Chile’s most isolated marine protected area: Implications for the conservation of the Galapagos shark, Carcharhinus galapagensis, and the yellowtail amberjack, Seriola lalandi

Abstract Marine protected areas (MPAs) are becoming a widely used tool for the conservation of biodiversity and for fishery management; however, most of these areas are designed without prior knowledge of the basic ecological aspects of the species that they are trying to protect. This study investigated the movement of two top predators: the Galapagos shark, Carcharhinus galapagensis, and the yellowtail amberjack, Seriola lalandi, in and around the Motu Motiro Hiva Marine Park (MMHMP) using MiniPAT satellite tags to determine the effectiveness of this MPA for the protection of these species. The Galapagos sharks (n = 4) spent most of their tag deployment periods inside the MMHMP. However, high intraspecific variability was observed in their movement dynamics. Daily individual maximum movements ranged from 17 to 58 km and the maximum distance from Salas y Gómez Island, the only emergent island within the MMHMP, ranged from 31 to 139 km. The maximum linear distance travelled for a female juvenile Galapagos shark (152 cm total length) was 236 km, which is greater than the maximum distance previously documented for juveniles of this species (&lt;50 km). For the yellowtail amberjack (n = 1), 91% of the satellite geolocations were within the MMHMP, with a maximum daily distance travelled of 6 km. The maximum distance travelled between points was 111 km and the maximum distance from Salas y Gómez Island was 62 km. All archival tagged fish spent most of their time at depths of &lt;50 m and never left the epipelagic zone. Daytime versus night‐time differences were pronounced in all individuals but showed high interindividual variability. This study provides a baseline on the movement of these two top predators in the MMHMP and provides valuable insights for the creation of MPAs in the region and elsewhere.