Development and Evaluation of a Chinook Salmon Smolt Swimming Behavior Model

Hydrologic currents and swimming behavior influence routing and survival of emigrating Chinook salmon in branched migratory corridors. Behavioral particle-tracking models (PTM) of Chinook salmon can estimate migration paths of salmon using the combination of hydrodynamic velocity and swimming behavior. To test our hypotheses of the importance of management, models can simulate historical conditions and alternative management scenarios such as flow manipulation and modification of channel geometry. Swimming behaviors in these models are often specified to match aggregated observed properties such as transit time estimated from acoustic telemetry data. In our study, we estimate swimming behaviors at 5 s intervals directly from acoustic telemetry data and concurrent high-resolution three-dimensional hydrodynamic model results at the junction of the San Joaquin River and Old River in the Sacramento-San Joaquin Delta, California. We use the swimming speed dataset to specify a stochastic swimming behavior consistent with observations of instantaneous swimming. We then evaluate the effect of individual components of the swimming formulation on predicted route selection and the consistency with observed route selection. The PTM predicted route selection fractions are similar among passive and active swimming behaviors for most tags, but the observed route selection for some tags would be unlikely under passive behavior leading to the conclusion that active swimming behavior influenced the route selection of several tagged smolts.

Movement shapes the structure of fish communities along a cross-shore section in the California Current

Pelagic fish communities are shaped by bottom-up and top-down processes, transport by currents, and active swimming. However, the interaction of these processes remains poorly understood. Here, we use a regional implementation of the APex ECOSystem Model (APECOSM), a mechanistic model of the pelagic food web, to investigate these processes in the California Current, a highly productive upwelling system characterized by vigorous mesoscale circulation. The model is coupled with an eddy-resolving representation of ocean currents and lower trophic levels, and is tuned to reproduce observed fish biomass from fisheries independent trawls. Several emergent properties of the model compare realistically with observations. First, the epipelagic community accounts for one order of magnitude less biomass than the vertically migratory community, and is composed by smaller species. Second, the abundance of small fish decreases from the coast to the open ocean, while the abundance of large fish remains relatively uniform. This in turn leads to flattening of biomass size-spectra away from the coast for both communities. Third, the model reproduces a cross-shore succession of small to large sizes moving offshore, consistent with observations of species occurrence. These cross-shore variations emerge in the model from a combination of: (1) passive offshore advection by the mean current, (2) active swimming towards coastal productive regions to counterbalance this transport, and (3) mesoscale heterogeneity that reduces the ability of organisms to return to coastal waters. Our results highlight the importance of passive and active movement in structuring the pelagic food web, and suggest that a correct representation of these processes is needed for realistic simulations with marine ecosystem models.

Pelagic larval polyclads that practice macrophagous carnivory

ABSTRACTWe report evidence that hatchling polyclads of several genera feed in the plankton on large prey. These ciliated swimmers, despite apparently lacking means to concentrate food or even detect it at a distance, subdue and consume fast-moving active-swimming plankters such as crustacean larvae and copepods, or molluskan veligers. We describe feeding events in captivity using videomicroscopy, and identify several wild-caught predatory pelagic polyclad larvae to genus or species level by DNA barcoding. Remarkably, one of these types is identified unambiguously with a species previously observed as Müller’s larvae, which live as conventional planktotrophs on an inferred diet of small phytoflagellates. Therefore we conclude first that while so-called “direct-developing” polyclad flatworms may hatch with juvenile-like morphology, at least some of these are functionally larvae. Second, that some species of polyclad have at least a triphasic life cycle, with a first larval stage living in the plankton on primary producers followed by a second larval stage living in the plankton by macrophagous carnivory, before presumably settling to the benthos for adult life.

Discovery of a colossal slickhead (Alepocephaliformes: Alepocephalidae): an active-swimming top predator in the deep waters of Suruga Bay, Japan

A novel species of the family Alepocephalidae (slickheads), Narcetes shonanmaruae, is described based on four specimens collected at depths greater than 2171 m in Suruga Bay, Japan. Compared to other alepocephalids, this species is colossal (reaching ca. 140 cm in total length and 25 kg in body weight) and possesses a unique combination of morphological characters comprising anal fin entirely behind the dorsal fin, multiserial teeth on jaws, more scale rows than congeners, precaudal vertebrae less than 30, seven branchiostegal rays, two epurals, and head smaller than those of relatives. Mitogenomic analyses also support the novelty of this large deep-sea slickhead. Although most slickheads are benthopelagic or mesopelagic feeders of gelatinous zooplankton, behavioural observations and dietary analyses indicate that the new species is piscivorous. In addition, a stable nitrogen isotope analysis of specific amino acids showed that N. shonanmaruae occupies one of the highest trophic positions reported from marine environments to date. Video footage recorded using a baited camera deployed at a depth of 2572 m in Suruga Bay revealed the active swimming behaviour of this slickhead. The scavenging ability and broad gape of N. shonanmaruae might be correlated with its colossal body size and relatively high trophic position.

Complex effect of caffeine and dioxidine on behavioral responses in mice in Porsolt test

Relevance. In light of the popularization of the use of caffeine-containing products, the question of the combined use of caffeine with substances exhibiting a toxic effect remains open. The doses of caffeine, which have a pronounced antidepressant effect, are also insufficiently studied. The aim of the study was to study the effect of repeated administration of caffeine and dioxidine on the behavioral responses of mice in the Porsolt test. Materials and methods. The experiment was carried out on 36 outbred male mice, divided into 6 groups. Experimental groups for 15 days of the study received caffeine at a dose of 40 mg/kg (first) or 100 mg/kg (second), dioxidine at a dose of 200 mg/kg (third), together with caffeine 40 mg/kg or 100 mg/kg, and dioxidine (fourth and fifth groups, respectively). The animals of the control group were injected with saline. To study the behavior, the Porsolt test was carried out, evaluating the following indicators on the 1st, 8th and 15th days of the experiment: the total time of immobilization, active swimming, climb, the number of grooming and shaking off acts. Results . The administration of caffeine at a dose of 40 mg/kg caused an increase in the time of active swimming and a decrease in the duration of immobilization on the 8th and 15th days. When caffeine was used at a dose of 100 mg/kg, an increase in the time of active swimming was noted with a single exposure, with an experiment duration of 8-15 days, an increase in the duration of immobilization was observed. Dioxidine caused a significant decrease in the time of active swimming and an increase in the duration of immobilization during all days of the experiment. The combined use of caffeine (40 mg/kg and 100 mg/kg) and dioxidine on the 1st day led to a decrease in immobilization and the time of active swimming. In both groups, 100 % animal mortality was observed by the 15th day. Conclusion. The results of the study indicate the presence of an antidepressant effect in caffeine at a dose of 40 mg/kg on the 8th and 15th days of the experiment and the absence of this effect in caffeine at a dose of 100 mg/kg with a duration of administration of 8-15 days. The use of dioxidine led to the absence of antidepressant activity and the presence of the opposite effect. The combined administration of caffeine (40 mg/kg and 100 mg/kg) and dioxidine led to 100 % mortality in the experimental groups by the 15th day of the experiment

Rethinking swimming performance tests for bottom-dwelling fish: the case of European glass eel (Anguilla anguilla)

Systematic experiments on European eel (Anguilla anguilla) in their juvenile, early life stage (glass eel), were conducted to provide new insights on the fish swimming performance and propose a framework of analysis to design swimming-performance experiments for bottom-dwelling fish. In particular, we coupled experimental and computational fluid dynamics techniques to: (i) accommodate glass eel burst-and-coast swimming mode and estimate the active swimming time (tac), not considering coast and drift periods, (ii) estimate near-bottom velocities (Ub) experienced by the fish, rather than using bulk averages (U), (iii) investigate water temperature (T) influence on swimming ability, and (iv) identify a functional relation between Ub, tac and T. Results showed that burst-and-coast swimming mode was increasingly adopted by glass eel, especially when U was higher than 0.3 ms-1. Using U rather than Ub led to an overestimation of the fish swimming performance from 18 to 32%, on average. Under the range of temperatures analyzed (from 8 to 18 °C), tac was strongly influenced and positively related to T. As a final result, we propose a general formula to link near-bottom velocity, water temperature and active swimming time which can be useful in ecological engineering applications and reads as $${\rm{U}}_{\rm{b}}=0.174\cdot \left({{\rm{t}}_{\rm{ac}}}^{-0.36}\cdot {\rm{T}}^{0.77}\right)$$ U b = 0.174 · t ac - 0.36 · T 0.77 .

Preliminary study of closed system transportation, rearing and observation of the eggs Oryzias javanicus (Bleeker 1854) from Tunda Island

Wild Oryzias javanicus from Tunda Island has potential as a native Indonesian aquatic ornamental fish and a model for research in the laboratory. The preliminary stage for raising wild fish is transporting from nature to the aquacul-ture environment. Generally, to minimize fish stress during transport in a closed system, anesthetics are added to the transport media. Furthermore, good adaptation in the aquaculture environment will lead to the process of reproduction as the ultimate goal of domestication of wild fish. The research objective is to analyze the transportation of closed systems and the rearing of O. javanicus post-transportation from Tunda Island. Research observations were carried out on behavior, survival, the number of eggs, and male: female sex ratio. Transport using an additional anesthetic treatment of 0.4 mL L-1 and without anesthesia, with fish density of 16 L-1. Anesthesia used is the commercial product Ocean Free® Special Arowana Stabilizer. Transportation is carried out for 11 hours. After that, rearing post-transportation is carried out for 16 days. The results showed that the transportation of O. javanicus can use a closed system without the addition of anesthesia with a density of 16 L-1 for 11 hours. In post-transport maintenance, fish begin active swimming on day 5, swim in groups continuously on day 6, start responding to natural food on day 3 and artificial feed on day 7, and produce a final survival of 91.67%. During maintenance, O. javanicus produces 104 eggs, 0.94 ± 0.06 mm in diameter and has an attaching filaments and a non-attaching filaments in the chorion. Oryzias javanicus is an egg depositor that can spawn with a 1: 1 and 1: 2 sex ratio.

Discriminating between sleep and exercise-induced fatigue using computer vision and behavioral genetics

Following prolonged swimming, Caenorhabditis elegans cycle between active swimming bouts and inactive quiescent bouts. Swimming is exercise for C. elegans and here we suggest that inactive bouts are a recovery state akin to fatigue. Previously, analysis of exercise-induced quiescent (EIQ) bouts relied on laborious manual observation, as existing automated analysis methods for C. elegans swimming either cannot analyze EIQ bouts or fail to accurately track animal posture during these bouts. It is known that cGMP-dependent kinase (PKG) activity plays a conserved role in sleep, rest, and arousal. Using C. elegans EGL-4 PKG, we first validate a novel learning-based computer vision approach to automatically analyze C. elegans locomotory behavior and distinguish between activity and inactivity during swimming for long periods of time. We find that C. elegans EGL-4 PKG function predicts EIQ first bout timing, fractional quiescence, bout number, and bout duration, suggesting that previously described pathways are engaged during EIQ bouts. However, EIQ bouts are likely not sleep as animals are feeding during the majority of EIQ bouts. We find that genetic perturbation of neurons required for other C. elegans sleep states also does not alter EIQ dynamics. Additionally, we find that EIQ onset is sensitive to age and DAF-16 FOXO function. In summary, we have validated a new behavioral analysis software that enabled a quantitative and detailed assessment of swimming behavior, including EIQ. We found novel EIQ defects in aged animals and animals with mutations in a gene involved in stress tolerance. We anticipate that further use of this software will facilitate the analysis of genes and pathways critical for fatigue and other C. elegans behaviors.

Influence of turbulence and in-stream structures on the transport and survival of grass carp eggs and larvae at various developmental stages

Understanding the response of grass carp to flow and turbulence regimes during early life stages is fundamental to monitoring and controlling their spread. A comprehensive set of hydrodynamic experiments was conducted with live grass carp eggs and larvae, to better understand their drifting and swimming patterns with 3 different in-stream obstructions: (1) a gravel bump, (2) a single cylinder, and (3) submerged vegetation. The hydrodynamic behavior of eggs and larvae with each obstruction was continuously monitored for about 85 consecutive hours. Transient spatial distributions of the locations of eggs and larvae throughout the water column were generated for each flow scenario. Results show that the active swimming capabilities of larvae allow them to seek areas of low turbulence and low shear stresses, and that eggs are susceptible to damage by high levels of turbulence, which was further corroborated with tests in an oscillating grid-stirred turbulence tank. Our study seeks to better inform field collection of grass carp during early life stages, and to guide the design of alternative approaches to control the dispersal of this invasive species in North America.

Multicellular behaviour enables cooperation in microbial cell aggregates

Oligosaccharides produced from the extracellular hydrolysis of biological materials can act as common goods that promote cooperative growth in microbial populations, whereby cell–cell aggregation increases both the per capita availability of resources and the per-cell growth rate. However, aggregation can also have detrimental consequences for growth, as gradients form within aggregates limiting the resource accessibility. We built a computational model, which predicts cooperation is restricted in dense cell aggregates larger than 10 µm because of the emergence of polymer and oligomer counter gradients. We compared these predictions to experiments performed with two well-studied alginate-degrading strains of Vibrio splendidus , which varied in their ability to secrete alginate lyase. We observed that both strains can form large aggregates (less than 50 µm), overcoming diffusion limitation by rearranging their internal structure. The stronger enzyme producer grew non-cooperatively and formed aggregates with internal channels that allowed exchange between the bulk environment and the aggregate, whereas the weak enzyme producer showed strongly cooperative growth and formed dense aggregates in which cells near the core mixed by active swimming. Our simulations suggest that the mixing and channelling reduce diffusion limitation and allow cells to uniformly grow in aggregates. Together, these data demonstrate that bacterial behaviour can help overcome competition imposed by resource gradients within cell aggregates. This article is part of a discussion meeting issue ‘Single cell ecology’.