Selective Tidal Stream Transport Research Articles

To hear or not to hear: selective tidal stream transport can interfere with the detectability of migrating silver eels in a Tidal River

Acoustic telemetry provides valuable insights into behavioural patterns of aquatic animals such as downstream migrating European eels (Anguilla anguilla), so called silver eels. The behaviour of silver eels during the migration is known to be influenced by environmental factors, yet so is the performance of acoustic telemetry networks. This study quantifies the impact of these environmental factors on both, migration behaviour and receiver performance to determine possible limiting conditions for detecting tagged eels in tidal areas. A dominance analysis of the selected models describing migration speed, activity and receiver performance was conducted following 234 silver eels that were tagged with acoustic transmitters and observed by a receiver network in the Ems River during two subsequent migration seasons. The results suggest a passive locomotion of silver eels during their downstream migration by taking advantage of selective tidal stream transport (STST). It is further shown that water temperature, salinity, turbidity, precipitation, and especially current velocity were major parameters influencing migration activity and speed. At the same time, analyses of the detection probability of tagged eels under varying environmental conditions indicated a decreased receiver performance during increased current velocities, meaning that high migration activity and -speed coincides with reduced detection probability. Consequently, there is a risk that particularly during phases of increased activity, migration activity may be underestimated due to reduced acoustic telemetry performance. To avoid bias in telemetry studies, it is, therefore, crucial to conduct range tests and adjust the receiver placement in areas and conditions of high current velocities.

Tidal and circadian patterns of European eel during their spawning migration in the North Sea and the English Channel

Technological advances in tracking methods enable the mapping of anguillid eel migration routes from continental habitats to their spawning sites in the ocean. However, the behaviour and orientation abilities of anguillids are still poorly understood, and have only rarely been studied on the continental shelf. Here we present the results of a study into the vertical and horizontal movement behaviour of 42 European eels (Anguilla anguilla L.) tagged with electronic tags that migrated through the North Sea and English Channel towards and into the Atlantic Ocean during their spawning migration. We used actograms, periodograms and linear mixed effects models to determine the periodicity and significance of the timing and pattern of vertical movement and activity. Overall, eels had a complex behavioural repertoire that included classical diel vertical migration (DVM), reverse DVM and vertical movement behaviours that synchronized with tidal patterns. All of the eels that were tracked showed one or more of these behaviours during their time at liberty, and many exhibited all of them. We also observed that the eels had a higher horizontal migration speed when the current in the favourable direction was stronger. This, together with the vertical movement synchronized with the tides, suggests the eels adopt selective tidal stream transport. Finally, tracked eels had a higher vertical movement range at night compared to daytime. We hypothesize that these behaviours are driven by bio-energetic efficient movement, navigation and predator avoidance.

Estimating migration speed of glass eels during their colonization of a Mediterranean lagoon.

Migration speed can have important evolutionary consequences as it can affect the timing of arrival, remaining energy reserves, and habitat choice. Environmental conditions and individual phenotypic traits can impact the migration speed of individuals. In this way, estimating migration speed is of particular importance, especially for species under strong management strategies and colonizing highly diversified habitats, as is the case for the European eel. However, estimating the migration speed of glass eels, which is the life stage when eels colonize continental habitats, presents challenges due to typically low re-capture probabilities and difficulties in tagging individuals. Using recruitment time series at two sites, one at the sea connection and another inland, we estimated the temporal lag between the two migration peaks to compute migration speed. Because we worked on the Mediterranean coasts and in a lagoon, the weak tidal amplitudes may inhibit individuals from efficiently performing the selective tidal stream transport. We obtained migration speed values coherent with the few values available in the literature for Atlantic estuaries. The values we obtained that are lower than those obtained for Atlantic estuaries are also coherent with the weak tides along the Mediterranean coasts and lead to necessary further studies to understand the migratory behavior of glass eels in such hydro-systems.

Predicting near-term, out-of-sample fish passage, guidance, and movement across diverse river environments by cognitively relating momentary behavioral decisions to multiscale memories of past hydrodynamic experiences

Predicting the behavior of individuals acting under their own motivation is a challenge shared across multiple scientific fields, from economic to ecological systems. In rivers, fish frequently change their orientation even when stimuli are unchanged, which makes understanding and predicting their movement in time-varying environments near built infrastructure particularly challenging. Cognition is central to fish movement, and our lack of understanding is costly in terms of time and resources needed to design and manage water operations infrastructure that is able to meet the multiple needs of human society while preserving valuable living resources. An open question is how best to cognitively account for the multi-modal, -attribute, -alternative, and context-dependent decision-making of fish near infrastructure. Here, we leverage agent- and individual-based modeling techniques to encode a cognitive approach to mechanistic fish movement behavior that operates at the scale in which water operations river infrastructure is engineered and managed. Our cognitive approach to mechanistic behavior modeling uses a Eulerian-Lagrangian-agent method (ELAM) to interpret and quantitatively predict fish movement and passage/entrainment near infrastructure across different and time-varying river conditions. A goal of our methodology is to leverage theory and equations that can provide an interpretable version of animal movement behavior in complex environments that requires a minimal number of parameters in order to facilitate the application to new data in real-world engineering and management design projects. We first describe concepts, theory, and mathematics applicable to animals across aquatic, terrestrial, avian, and subterranean domains. Then, we detail our application to juvenile Pacific salmonids in the Bay-Delta of California. We reproduce observations of salmon movement and passage/entrainment with one field season of measurements, year 2009, using five simulated behavior responses to 3-D hydrodynamics. Then, using the ELAM model calibrated from year 2009 data, we predict the movement and passage/entrainment of salmon for a later field season, year 2014, which included a novel engineered fish guidance boom not present in 2009. Central to the fish behavior model’s performance is the notion that individuals are attuned to more than one hydrodynamic signal and more than one timescale. We find that multi-timescale perception can disentangle multiplex hydrodynamic signals and inform the context-based behavioral choice of a fish. Simulated fish make movement decisions within a rapidly changing environment without global information, knowledge of which direction is downriver/upriver, or path integration. The key hydrodynamic stimuli are water speed, the spatial gradient in water speed, water acceleration, and fish swim bladder pressure. We find that selective tidal stream transport in the Bay-Delta is a superset of the fish-hydrodynamic behavior repertoire that reproduces salmon movement and passage in dam reservoir environments. From a cognitive movement ecology perspective, we describe how a behavior can emerge from a repertoire of multiple fish-hydrodynamic responses that are each tailored to suit the animal’s recent past experience (localized environmental context). From a movement behavior perspective, we describe how different fish swim paths can emerge from the same local hydrodynamic stimuli. Our findings demonstrate that a cognitive approach to mechanistic fish movement behavior modeling does not always require the maximum possible spatiotemporal resolution for representing the river environmental stimuli although there are concomitant tradeoffs in resolving features at different scales. From a water operations perspective, we show that a decision-support tool can successfully operate outside the calibration conditions, which is a necessary attribute for tools informing future engineering design and management actions in a world that will invariably look different than the past.

Modes of ingress by larvae and juveniles of marine fishes into estuaries: From microtidal to macrotidal systems

AbstractWe review published research on the ingress of larvae and early juveniles of marine fishes into estuaries subjected to different tidal regimes and provide perspectives on the abilities and responses of these early‐life stages to the physico‐chemical, hydrodynamic and biological drivers that facilitate such ingress. We focus on documenting ingress and the mechanisms employed by early‐stage fishes from coastal waters to enter different types of microtidal and macrotidal estuaries but also include information on ingress into mesotidal systems. Spawning localities for estuary‐associated marine fishes are assessed with respect to ontogeny of larvae and their ability to ingress estuaries during the preflexion and postflexion stages. The processes and physico‐chemical cues employed by larvae and early juveniles to locate estuaries are reviewed, with olfactory cues being recognised as especially important. Particular emphasis is directed to vertical migratory behaviours and selective tidal stream transport (STST) employed by many larvae ingressing macrotidal estuaries, contrasting with mainly passive flood‐tide entry and active swimming modes typically used by larvae and early juveniles that enter microtidal estuaries and estuarine lakes and lagoon systems.

Mechanisms for longitudinal transport on early life stages in benthic-pelagic fishes within a tide-dominated estuary

Mechanisms that control the longitudinal transport of larvae and juveniles in nursery grounds such as estuaries are reported for some species. However, the behaviour and population consequences of these mechanisms are still uncertain. In this study, we tested selective tidal-stream transport from the along-channel (up- and downstream) and cross-channel (from one margin to the other) perspectives for two kinds of fish: estuarine-resident gobies (Pomatoschistus spp.) and marine estuarine-opportunistic anchovies (Engraulis encrasicolus). Three cruises were conducted in the lower Guadalquivir estuary, on the ebb and on the flood of spring tides in summer. Plankton samples were collected across a channel section, at three stations (one in the middle of the channel and two in adjacent shallower areas), near the surface and near the bottom simultaneously. In addition, multiple physico-chemical variables (temperature, turbidity, dissolved oxygen, pH, salinity, chlorophyll-a, along with wind and current direction and velocity) were measured to examine the different correlations used by the studied fish in their strategies. The benthic distribution of gobies indicated that they used flood currents near the bottom of lateral (shallow) areas to ingress into and remain in the estuary, temperature and/or dissolved oxygen being their main possible cues. On the contrary, the anchovies were more abundant near the surface, especially on the ebb tide, showing downstream advection, which was mainly influenced by salinity. However, the largest individual anchovies in the lateral/shallow zones suggested a behavioural ontogeny, which, together with wind induced transport, could contribute to their retention. This comparison also enhanced the knowledge of the habitat distribution of two species common and abundant in estuaries, anchovies and gobies.

Agent-based modelling of juvenile eel migration via selective tidal stream transport

Recruitment of temperate eel species Anguilla anguilla, A. rostrata &A. japonica has declined over the last few decades due to human activities, such as overfishing and construction of migratory barriers (e.g. dams, weirs and sluices) and hazardous energy infrastructure (e.g. turbines, intakes and outfalls). Numerical models, substantiated with data from field and laboratory studies, can potentially predict and quantify the relative impacts of such activities, thereby assisting in the sustainable management of eel populations. Here, we present an agent-based model (ABM) of juvenile eel migration up estuaries. The model includes relevant eel behaviours and environmental conditions that, according to the literature, influence upstream migration. Crucially, by assessing the local salinity gradient and relative flow direction, the modelled eels (agents) self-determine whether the tide is flooding or ebbing and orientate themselves for navigation, with no top-down instructions. This allows the agents to decide which particular behaviour to undertake as part of Selective Tidal Stream Transport (STST). The developed ABM is coupled to a hydrodynamic model of the Thames Estuary and the results substantiated by comparison against eel trap data. Combinations of the various STST behaviours are systematically tested and the influence they have on up-estuary migration is assessed in terms of relative energy expenditure. The parameterised model is then used predictively at Milford Haven Waterway to investigate potential impacts on the juvenile eel population due to entrainment in a power plant cooling water intake and outfall. Results from the Thames model case study indicate that including bed anchoring behaviour is essential for achieving a good comparison with the eel trap data and the choice of salinity detection threshold is also important. If daylight avoidance (diel) behaviour is not included, the most energy efficient migration is achieved using just two STST behaviours (ebb tide bed anchoring and upward migration during flood). With diel behaviour included, energy expenditure is greater, but some efficiency is regained by including all of the STST behaviours. For the Milford Haven case study, the model predicted a juvenile eel intake and outfall entrainment rate of 2.0% and 4.7%, respectively. It is concluded that the ABM is a valuable tool for assessing potential impacts on the recruitment of eels (extendable to other species) and could be used to assist in site-selection and low impact design of energy infrastructure in tidal environments.

Rhythmic activity of inshore migration of tropical freshwater glass eels of the genus Anguilla

Compared with temperate Anguilla, little is known about the early marine migration and recruitment mechanisms of these tropical eels. To understand the ecological and behavioural mechanisms of their inshore migration in tropical Anguilla, systematic research on their periodicity of inshore migration was conducted for 24 h over 9 to 13 consecutive days before and after the new moon dates four times in one year. Glass eel (juvenile) collections (151 to 4371 specimens during each survey period) in the Poigar River, north Sulawesi Island, Indonesia indicated a lunar periodicity, in which peak recruitment continued for 2 to 4 days during the new moon period; then, the recruitment sharply decreased before and after the new moon. Daily glass eel migration occurred in two peaks during the ebb (20:00) and flood (02:00) tides, while there was no significant different glass eel recruitment between the flood tide and ebb tides. Although the “selective tidal stream transport” that glass eels utilize during the flood tide for recruitment is widely accepted to be the main mechanism of inshore migration behaviour through estuaries to freshwater habitats for temperate glass eels, we did not find this mechanism during this study. These results suggest that the main recruitment mechanism for tropical glass eels may be associated with both endogenous rhythms (biological clock) and exogenous factors (tidal orientation) in the study site. The rhythmic activity of migrating tropical glass eels found in this study also contributes not only to understanding the biological and ecological implications but also provides clues for stock management and conservation of Anguilla, which have been critically declining in recruitment worldwide in recent decades.

Persistent Hydrodynamic Cues Elicit Orientation-Specific Behavioral Sensitivities and Kinematic Responses in Dispersed Crab Larvae

The estuarine mud crab Panopeus herbstii navigates a complex, but structured, hydrodynamic environment throughout its life history. The effects of hydrodynamic cues associated with turbulent flows on larval behavior are relatively well understood in the context of selective tidal stream transport (STST) phenomena during the dispersed (pelagic) larval stages preceding benthic settlement. In contrast, the potential relevance of hydrodynamic cues associated with spatiotemporally persistent flow features, which are typical of estuarine regions of enhanced productivity such as fronts and clines, remains much less certain. To investigate the behavioral relevance of persistent hydrodynamic cues, larval assays were conducted in a flume system that uses a laminar slot jet to produce steady fluid shear layers. Further, to ascertain whether or not the spatial orientation of the shear layers relative to gravity significantly affected larval behavior, assays were conducted in upwelling, downwelling, and horizontal shear flows, corresponding to the direction of the bulk flow produced by the jet. The flow was quantified using particle image velocimetry (PIV) and tuned to produce ecologically-relevant hydrodynamic conditions for larval assays. Changes in larval swimming kinematics show a distinct response to shear flows in all orientations relative to no-flow conditions, and the macro effect of these changes is to enhance depth-keeping and induce area-restricted search behaviors. Furthermore, the specifics of larval behavioral responses depend on the directional orientation of the shear flow, and the statistical properties of the strength of the hydrodynamic cue (vorticity) eliciting these responses are also shown to be shear flow orientation-specific. Orientation-specific hydrodynamic sensitivity and behavioral response strategies in the presence of persistent hydrodynamic cues may enable larvae to effectively forage and sample to locate and exploit nearby resource patches, while also inducing dispersal trajectories towards favorable benthic settlement habitats through depth regulation and effective STST. In this regard, hydrodynamic cues associated with spatiotemporally persistent flow features are likely fundamental drivers of decapod crab larvae behavior and may act as another mechanism of larval patchiness by directly impacting finescale population distributions and resultant dispersal trajectories.

Adult Sockeye Salmon Assessment in a Tidal, Turbid River: A Comparison of Sonar and Test Fishing Methods

AbstractThe feasibility of using sonar in Alaska's lower Kvichak River, a region with a 3.8 m tidal flux, to assess the abundance of adult Sockeye Salmon Oncorhynchus nerka was evaluated as a replacement for an in‐river gill‐net test fishery. Test fish indices are one tool that is used to manage commercial and subsistence fisheries in Bristol Bay. On this river, an observation tower project near the clear headwaters provides accurate abundance estimates for this species, but fishery managers require timelier estimates for in‐season daily management. The lower‐river test fish index is timelier, but it is less precise than tower estimates are. We had to determine whether to replace the test fish project with sonar based on how well each compared with tower estimates and an assessment of their cost and effort. Two dual‐frequency identification sonars (DIDSONs) were deployed along one bank of the lower river (one pointed toward shore and one away from shore) to assess salmon passage across all tidal stages in an attempt to produce an index with higher precision. Compared with the tower estimates, the test fish index showed a slightly stronger correlation in each of the three study years than the sonar index did, despite the stronger sampling power of the sonar. The test fish and sonar indices were strongly correlated. In the lower river, upriver salmon migration (85–98%) occurred primarily during ebb tides and downriver passage (97–100%) during flood tides, indicating that salmon do not use selective tidal stream transport to minimize their energy expenditures in this river. We were able to successfully use fixed‐location sonar in a tidal nearshore region to produce an index of fish abundance. Our recommendation was to continue the test fishing project rather than to replace it with sonar because of the similarity between their indices and the higher cost of the sonar project.

Estimating the energetic savings for green sturgeon moving by selective tidal stream transport

As fish move, they incur an energetic cost of transport (COT) from the use of aerobic muscles. Water currents are an integral component of the physical world of fishes, and if water currents are present, fish may pay higher costs fighting the currents, or may use the currents to facilitate movement and reduce COT. Some fish use “selective tidal stream transport” (STST) to move efficiently through tidal regions, swimming into the water column when the current is favorable, and returning to the bottom during opposing tides. This behavior has been reported in marine fish migrating through tidal habitats, but it is also likely of value in daily movements of fish residing in those habitats. It is extremely difficult to directly measure COT in wild fish; however, it is possible to combine analysis of field telemetry data of individual swimming efforts and measurements of metabolic costs of swimming from respirometry in order to estimate the COT in the wild, and to calculate the costs or savings of swimming with or against currents. We describe this novel analytical approach and demonstrate it using data from two green sturgeon tracked in San Francisco Bay, California. In this analysis, when moving at the surface and employing STST, the fish benefited from the current, swimming within 85.5% of optimal efficiency. When conducting non-STST movements near the bottom, swimming was less efficient, with a COT similar to swimming directly into the current. These results suggest that green sturgeon may opportunistically utilize stream transport in daily movements, swimming at the surface and orienting with currents to achieve substantial energetic savings.

Selective tidal stream transport in silver European eel (Anguilla anguilla L.) – Migration behaviour in a dynamic estuary

Different fish species use selective tidal stream transport (STST) to efficiently migrate through strong tidal systems to complete their life cycle, but the use of STST by silver European eels (Anguilla anguilla L.) is still controversial. In this study, we found strong evidence that silver European eels apply STST. The results illustrate that eels can distinguish between ebb and flood and suggest that tides play a role in orientation, either directly or indirectly. The general migration speed was higher in the downstream part of the estuary compared to the upstream part, while tidal migration speed was equal in both parts, indicating that eels migrated more consistently in the downstream part. The results of this study give insight in how a diadromous species migrates through an estuary and underline the importance of the tides.

Not easy to catch: multiple covariates influence catch rates of brown shrimp (Crangon crangon L.), potentially affecting inferences drawn from catch and landings data

Abstract Brown shrimps (Crangon crangon) occur in high densities in the southern North Sea and support a large, but so far unmanaged fishery with >500 vessels. Cohort-based stock assessment is not possible, and catch per unit effort from scientific surveys and commercial landings are the only variables collected. Landings per unit effort are currently used to approximate the state of stock and to trigger catch restrictions, but, although decisive in interpreting unit catches or landings, factors affecting catch rates are rarely understood. Using data from two long-term (1997–2010) scientific surveys conducted in autumn and winter, respectively, in the southern North Sea and from a vertically resolving stow net deployed at two stations in the German Wadden Sea (2005–2007), we investigate the effects of season, reproductive state, size, tidal state, daylight, and water depth on catch rates of brown shrimp. Log-linear random intercept models revealed an influence of all factors examined on the catch rate. Depth had a clear effect on the composition of size and reproductive state, supporting the hypothesis that brown shrimp utilize selective tidal stream transport to migrate to depths preferred during certain periods within their life cycle. The vertical distribution of brown shrimp across the water column revealed that on average two thirds to three quarters of the brown shrimps were located above reach of the standard shrimp catching gear. Our findings indicate that multiple factors and interactions affect catch rates of brown shrimp and, thus, need to be accounted for when interpreting unit catches or landings for management purposes. We suggest that brown shrimps are not primarily demersal, and that stock size estimates solely relying on beam trawl data may underestimate the true density of shrimps per area.

Energetically efficient behaviour may be common in biology, but it is not universal: a test of selective tidal stream transport in a poor swimmer

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 584:161-174 (2017) - DOI: https://doi.org/10.3354/meps12352 Energetically efficient behaviour may be common in biology, but it is not universal: a test of selective tidal stream transport in a poor swimmer Sergio Silva1,2,*, Consuelo Macaya-Solis1, Martyn C. Lucas1 1Department of Biosciences, University of Durham, South Road, Durham DH1 3LE, UK 2Departamento de Zooloxía, Xenética e Antropoloxía Física, Facultade de Bioloxía, Campus Vida, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain *Corresponding author: sergio.silva@usc.es ABSTRACT: Selective tidal stream transport (STST) is a common migration strategy for a wide range of aquatic animals, facilitating energetically efficient transport, especially of species considered poor swimmers. We tested whether this mechanism applies during the upstream migration of a poor swimmer, the European river lamprey Lampetra fluviatilis, in a macrotidal estuary. Lamprey (n = 59) were acoustically tagged and tracked in a 40 km section of the River Ouse estuary (NE England) in autumn 2015. Against expectations, lamprey did not use STST and migrated upstream during flood, ebb and slack tide periods. Lamprey also migrated during both day and night in most of the study area, probably due to the high turbidity. The global migration speed (all individuals, over the entire track per individual) was (mean ± SD) 0.15 ± 0.07 m s-1. The migration speed varied significantly between tidal periods (0.38 ± 0.04 m s-1 during flooding tides, 0.12 ± 0.01 m s-1 during ebbing tides and 0.28 ± 0.01 m s-1 during slacks). It was also higher in areas not affected by tides during periods of high freshwater discharge (0.23 ± 0.08 m s-1) than in affected areas (0.17 ± 0.14 m s-1). If the energetic advantages of STST are not employed in macrotidal environments, it is likely that the fitness costs of that behaviour exceed potential energy savings, for example due to increased duration of exposure to predation. In conclusion, STST is evidently not universal in relatively poor swimmers; its use can vary between species and may vary under different conditions. KEY WORDS: Energy efficiency · Selective tidal stream transport · Fish migration · Telemetry · Estuary · Anadromous · River lamprey · Lampetra fluviatilis Full text in pdf format Supplementary material PreviousNextCite this article as: Silva S, Macaya-Solis C, Lucas MC (2017) Energetically efficient behaviour may be common in biology, but it is not universal: a test of selective tidal stream transport in a poor swimmer. Mar Ecol Prog Ser 584:161-174. https://doi.org/10.3354/meps12352 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 584. Online publication date: December 07, 2017 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2017 Inter-Research.

Modeling the migration of the American eel in the Gulf of St. Lawrence

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 549:183-198 (2016) - DOI: https://doi.org/10.3354/meps11706 Modeling the migration of the American eel in the Gulf of St. Lawrence Mélanie Béguer-Pon1,2,*, Kyoko Ohashi2, Jinyu Sheng2, Martin Castonguay3, Julian J. Dodson1 1Département de Biologie, Université Laval, Québec City, Québec G1V 0A6, Canada 2Department of Oceanography, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada 3Institut Maurice-Lamontagne/Fisheries and Oceans Canada, CP 1000, Mont-Joli, Québec G5H 3Z4, Canada *Corresponding author: melanie.beguer@gmail.com ABSTRACT: Telemetry experiments allow documentation of aquatic animal movements in the ocean, and numerical models can contribute to our understanding of the mechanisms underlying the observed movement patterns. In this study, we used mature (silver-stage) American eel Anguilla rostrata migration out of the St. Lawrence Estuary (SLE)-Gulf of St. Lawrence (GSL) system to illustrate how an individual-based model coupled with a 3-dimensional ocean circulation model can help us understand fish behaviour, and complement ongoing and future telemetry experiments. A suite of 23 numerical simulations that combined various vertical and horizontal swimming behaviours of virtual eels (‘v-eels’) was conducted to evaluate which behaviours most closely matched the observed migratory patterns of silver eels in the GSL. Results indicated that v-eels migrating through the SLE-GSL must employ active swimming and complex orientation strategies in order to migrate in the time suggested by telemetry experiments. The use of selective tidal stream transport is sufficient for v-eels to escape entrapment in the Estuary; however, this behaviour requires active swimming rather than simply drifting in the direction of the appropriate currents in the Estuary in order to eventually exit the GSL within the time frame observed in the field. Orientation towards higher salinity and/or greater water depths in the Gulf was not sufficient for v-eels to successfully escape the GSL, suggesting the use of other variables such as the geomagnetic field gradient is required. The model also allows exploration of the potential effects of climate change on the duration of migration, through changes in hydrological conditions. KEY WORDS: Orientation cues · Telemetry · Particle-tracking · Spawning migration · Ocean Tracking Network · Ocean circulation model · Anguilla rostrata Full text in pdf format PreviousNextCite this article as: Béguer-Pon M, Ohashi K, Sheng J, Castonguay M, Dodson JJ (2016) Modeling the migration of the American eel in the Gulf of St. Lawrence. Mar Ecol Prog Ser 549:183-198. https://doi.org/10.3354/meps11706 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 549. Online publication date: May 10, 2016 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2016 Inter-Research.

Periodicities of inshore migration and selective tidal stream transport of glass eels, Anguilla japonica, in Hamana Lake, Japan

During inshore migration, glass eels experience great environmental changes they must adapt to, but there have been few studies on the behavior of juvenile Japanese eels, Anguilla japonica, entering estuaries. To investigate the relative effects of periodic environmental changes on their inshore migration and ascending behavior from the bottom to swim with flood tidal currents, year-round collections were carried out from December 2003 to December 2005 inside Hamana Lake, Japan, where strong tidal flows occur. Glass eel collections (N = 543) near the inlet to the lake indicated that recruitment occurred mainly in winter from November to May. Time-series autocorrelation analysis of average daily catch rates found negative autocorrelation coefficients at 16–20 days periodicities and positive ones at 30–32 days periodicities in the 2004–2005 season, suggesting that the amount of recruiting glass eels fluctuates with a lunar cycle. Abundances of glass eels showed a diel rhythm and a tidal rhythm with eels appearing only at night and catches during flood tide being higher than during ebb tide, indicating ‘Selective Tidal Stream Transport’ that eels utilize flood tidal-streams selectively at night to migrate inshore. The generalized additive models (GAM) for the abundance suggested that relatively long timescale factors such as ‘recruitment season’ and ‘lunar age’ could affect the abundance of glass eels. The GAM for glass eel presence/absence indicated that the timing of glass eel ascending into the water column during flood tide at night was at 150–180 min after low tide, which tended to synchronize with the rise of water temperature caused by the inflow of warm water from the Pacific coast outside the lake. Results suggested that a temperature increase at the beginning of flood tide may be a cue for the ascending behavior, or at least could be a zeitgeber of the circatidal rhythm regulating the ascending behavior.

Investigating the Effect of Oceanographic Conditions and Swimming Behaviours on the Movement of Particles in the Gulf of St. Lawrence Using an Individual-Based Numerical Model

ABSTRACTIn this study an individual-based numerical model with three-dimensional (3D) and time-dependent fields of circulation and hydrography is used to examine the effects of the physical environment and various biological behaviours on the distribution and movement of particles in the Gulf of St. Lawrence and adjacent waters. The 3D circulation and hydrographic fields are simulated by a numerical ocean circulation model. The model domain covers the St. Lawrence Estuary (SLE), the Gulf of St. Lawrence (GSL), the Scotian Shelf, the Gulf of Maine, and their adjacent waters. The basis of the individual-based model is a numerical scheme that tracks the movement of particles carried by ocean currents. Several swimming behaviours of marine animals are considered with efficient seaward migration in the GSL as the goal. Electronic tagging data for the American eel (Anguilla rostrata) are used as guidance in specifying the behaviours. It is demonstrated that particles that undergo an observed behaviour, known as selective tidal stream transport, are able to exit the SLE more efficiently than particles that are carried passively by the 3D ocean currents. Outside the SLE, particles that search for and swim towards higher salinity move further downstream than those that have a preference for deeper water or swim in random directions.

Smells Like Home: The Role of Olfactory Cues in the Homing Behavior of Blacktip Sharks, Carcharhinus limbatus.

Animal navigation in the marine environment is believed to be guided by different sensory cues over different spatial scales. Geomagnetic cues are thought to guide long-range navigation, while visual or olfactory cues allow animals to pinpoint precise locations, but the complete behavioral sequence is not yet understood. Terra Ceia Bay is a primary nursery area for blacktip sharks, Carcharhinus limbatus, on southwestern Florida's Gulf of Mexico coast. Young-of-the-year animals show strong fidelity to a specific home range in the northeastern end of the bay and rapidly return when displaced. Older juveniles demonstrate annual philopatry for the first few years, migrating as far south as the Florida Keys each fall, then returning to Terra Ceia Bay each spring. To examine the sensory cues used in homing, we captured neonate (<3 weeks old) blacktip sharks from within their home range, fitted them with acoustic tags, and translocated them to sites 8 km away in adjacent Tampa Bay and released them. Intact animals returned to their home range, within 34 h on average, and remained there. With olfaction blocked, fewer animals returned to their home range and they took longer to do so, 130 h on average. However, they did not remain there but instead moved throughout Terra Ceia Bay and in and out of Tampa Bay. Since sharks from both treatments returned at night in tannic and turbid water, vision is likely not playing a major role in navigation by these animals. The animals in this study also returned on incoming or slack tides, suggesting that sharks, like many other fish, may use selective tidal stream transport to conserve energy and aid navigation during migration. Collectively, these results suggest that while other cues, possibly geomagnetic and/or tidal information, might guide sharks over long distances, olfactory cues are required for recognizing their specific home range.

Modeling Larval Transport and Settlement of Pink Shrimp in South Florida: Dynamics of Behavior and Tides

AbstractThe pink shrimp Farfantepenaeus duorarum, one of the commercially important Penaeidae, reproduces offshore of the southwest Florida (SWF) shelf. Larvae migrate to nursery grounds in estuarine Florida Bay. Using a numerical approach, we investigated the role of spawning location, larval traits, and physical forces on the transport of pink shrimp larvae. First, the Regional Oceanic Modeling System that is based on tides, air–ocean fluxes, and freshwater flows was used to simulate the SWF shelf oceanography. The model replicates the tides, winds, salinity, currents, and seasonality of the shelf. Secondly, the Regional Oceanic Modeling System was coupled offline with the Connectivity Modeling System, in which virtual larvae were released near the surface from two spawning sites, Dry Tortugas and Marquesas, and tracked until the time for settlement (about 28–30 d). Virtual larvae moved vertically in the water column following ontogenetic behaviors previously observed in the field: diel vertical migration (DVM) and selective tidal stream transport (STST). Lagrangian trajectories indicated that migration paths changed radically between summer and winter during model years (1995–1997). Maximum settlements occurred in summer by larvae crossing the SWF shelf, while the lowest settlement occurred in winter by larvae moving through passes in the Florida Keys. Modeling results demonstrated an effective east‐northeast transport across the SWF shelf during summer as a result of the tidal currents, the subtidal currents, and the combined DVM and STST behaviors. The current phase captured during the initial DVM period was critical to determine the direction in which larvae move, favorable (east and northward) or unfavorable (south and westward), before the STST behavior captures the eastward tidal current that brings larvae to the nursery grounds. Unfavorable currents were driven by the summer easterlies and low salinities at the coast. Results indicated that Marquesas is the more effective spawning ground, with 4.5 times more likely settlement of originating larvae compared with Dry Tortugas. Model‐estimated seasonal settlement patterns concurred with postlarval influxes previously observed at Florida Bay boundaries.Received June 26, 2014; accepted December 7, 2014

Hydrostatic pressure affects selective tidal stream transport in the North Sea brown shrimp (Crangon crangon).

The brown shrimp (Crangon crangon) is a highly abundant invertebrate in the North Sea, with its life cycle stages ranging from deep offshore spawning to shallow onshore nursery areas. To overcome the long distances between these two habitats, brown shrimp are suspected to use selective tidal stream transport (STST), moving with the cyclic tide currents towards their preferred water depths. However, it is not known which stimulus actually triggers STST behavior in brown shrimp. In this work, we determined the influence of different hyperbaric pressures on STST behavior of juvenile brown shrimp. Brown shrimp activity was recorded in a hyperbaric pressure chamber that supplied constant and dynamic pressure conditions simulating different depths, with and without a tidal cycle. Subsequent wavelet and Fourier analysis were performed to determine the periodicity in the activity data. The results of the experiments show that STST behavior in brown shrimp varies with pressure and therefore with depth. We further show that STST behavior can be initiated by cyclic pressure changes. However, an interaction with one or more other environmental triggers remains possible. Furthermore, a security ebb-tide activity was identified that may serve to avoid potential stranding in shallow waters and is 'remembered' by shrimp for about 1.5 days without contact with tidal triggers.