Behavioral Responses in Zebrafish (Danio rerio) Exposed to Heavy Metal and Insecticide Induced Stress

Background: Changes in fish behavior can help identify accidental chemical pollution. Heavy metals and pesticides are two of the most found pollutants to investigate the different behavioral responses of fish to these two types of pollutants exposure. Methods: Real-time computer imaging was utilized to record parameters of fish behaviors, including swimming speed, turning frequency, depth and distance between fish. Deltamethrin and cadmium were 0.015 ppm and 3.5 ppm, respectively. It was conducted for a total period of 180 min. Fish behaviors were recorded with dechlorinated water during the first 60 mins, then deltamethrin and cadmium was introduced to observe behavioral responses of zebrafish during the next 120 mins. Result: As a result of increased swimming activity, the first response of zebrafish is avoidance followed by a changed distribution in the test chamber. The duration of hyperactivity during deltamethrin exposure was lasted 35 minutes larger than Cd exposure and the average swimming depth showed totally different trends with increased from 140 mm to 226 mm during deltamethrin exposure but decreased from 161 to 84 mm during cadmium exposure. It is proved that these different responses do exist under in the two chemicals studied and this may contribute to the development of biological early warning system to separate accidental chemical pollution types.

Biology and Environmental Preferences of Wahoo, Acanthocybium solandri (Cuvier, 1832), in the Western and Central Pacific Ocean (WCPO)

Wahoo Acanthocybium solandri is a common bycatch pelagic species in oceanic fisheries targeting tuna and tuna-like species. Biology and environmental preferences are important parameters in understanding life history of fish species including wahoo. Despite the socio-economic importance of wahoo in many coastal countries, little is known about their biological and fisheries information in the Western and Central Pacific Ocean (WCPO). These parameters were analyzed on the basis of samples collected via the Chinese tuna long-line Fishery Observer Programme in 2012. Results obtained from this study show that the fork length (FL) of wahoo ranged from 59 to 169 cm with an average of 111.3 cm, and two dominant size groups were identified at 100 to 130 cm for males and 90 to 130 cm for females. Body size did not significantly differ between female and male wahoo specimens. Wahoo specimens expressed a positive allometric growth (b = 3.183), and the sex ratio was 1.9:1 (female/male), which differed significantly between both sexes. Only female wahoo were observed in catches of FL > 150 cm. The estimated lengths at 50% maturity (FL50) of female and male wahoo were 84 cm and 83 cm, respectively. Gonadosomatic index (GSI) of wahoo was at its peak in November, and on the basis of the stomach content analysis, wahoo mainly preyed on fish (84.64%), cephalopods (14.26%), and crustaceans (1.1%), found on the basis of prey number. The optimal swimming depth and water temperature of wahoo in the WCPO were found to range between 70 and 110 m and 23.1 and 24 °C, respectively. The updated life history information presented in this work helps to address current data limitations and provides critical information for future assessments of wahoo stocks in the WCPO.

An overview of behavioral, physiological, and environmental sensors used in animal biotelemetry and biologging studies

Background The ability to remotely monitor the behavior of animals and their interactions with their environment has revolutionized how ecologists conduct studies. The creative use and placement of sensors on both biologging and biotelemetric platforms can greatly expand the amount of information that can be garnered from ecological studies. Results Sophisticated transmitters and data loggers, which once were built by the biologists that used them, are available off the shelf from many commercial manufacturers. The ability to purchase a wide variety of electronic tags has allowed for a wider adoption of electronic tags across ecology, but has resulted in many biologists utilizing them with little understanding of how they function. The purpose of this review is to provide a reader-friendly description of the many sensors available to monitor the behavior, physiology, and environment of both terrestrial and aquatic animals. Our approach here is firstly to describe the electrical and mechanical principles behind each type of sensor and secondly to present one or two classic examples of how they have been used to provide insights into the biology of species from a diversity of taxa. Behavioral sensors that record the speed, acceleration, tilt angle, and direction of movement of an animal as well as its swimming depth or flight altitude will be described. Additional sensors are mentioned that detect feeding and spawning behavior as well as the proximity to conspecifics, prey, and predators. Physiological sensors will be described that monitor muscular, sensory, brain, gastric activity as well as body temperature, and sound production. Environmental sensors will be described that measure irradiance, dissolved oxygen, and magnetic field intensity. It is our hope that this review serves as springboard for biologists to develop innovative ways to learn more about their subjects using the myriad sensors that are available today, and the exciting new sensors to be developed in the future.

The migration of stocked, trapped and transported, and wild female American silver eels through the Gulf of St. Lawrence

The stocking of juvenile eels and trap and transport programs of large yellow (American) eels (Anguilla rostrata) were initiated in Ontario to mitigate mortalities observed at hydroelectric dams and to increase escapement from the upper St. Lawrence River and Lake Ontario (Canada). A total of 380 migrating female silver eels (stocked, trapped and transported, and wild) were tagged with acoustic transmitters between 2011 and 2014. Their migration and escapement at the exit of the Gulf of St. Lawrence, the Cabot Strait, were recorded using acoustic receivers. Escapement rates varied between 8.9% and 20.0% annually (mean = 11.4%). A high proportion of stocked eels were detected (N = 27 of 43 detected at Cabot Strait), demonstrating their ability to escape the Gulf. No differences in migration speed or crossing locations at Cabot Strait were found among the three categories. Eels crossing Cabot Strait did not display diel and tidal patterns, but their estimated swimming depth indicated diel vertical migrations. The low escapement rates observed may be related to predation events and (or) the low and variable detection efficiency of the acoustic receivers’ line.

Refining the interpretation of oxygen isotope variability in free-swimming organisms

Serially sampled δ18O from fossil and modern cephalopods may provide new insight into the behavior and longevity of individuals. Interpretation of these data is generally more difficult than similar data from bivalves or brachiopods because the measured δ18O from shell combines both seasonal change and depth change over the life of an individual. In this paper, a simple null model is presented combining the three fundamental controls on a measured δ18O profile in a free-swimming organism: swimming behavior, seasonal water column temperature change, and time averaging in sampling. Model results indicate that seasonal variability in δ18O in a free-swimming organism can be interpreted in locations with strong seasonality through most of the swimming range but is complicated by swimming velocity and is sometimes best expressed by changes in δ18O variance rather than simple sinusoidal patterns. In other locations with a stable thermocline or seasonal ranges in only a small portion of the water column, no variability caused by seasonality would be expected. Furthermore, large ranges of δ18O (~4‰) are possible within and between individuals in settings with persistent thermoclines like the tropics, depending on the swimming depth limits and behavior of individuals. These results suggest that future interpretation of serially sampled δ18O should consider seasonal water column variation from either modern or modeling sources in addition to comparison to co-occurring benthic and planktic organisms. Additionally, this modeling casts doubt on the promise of isotope sclerochronology alone as a growth chronometer in ammonites and other free-swimming fossil organisms and highlights the need for other methods of quantitatively determining age.

Herring submesoscale dynamics through a major spawning wave: duration, abundance fluctuation, distribution, and schooling

In this study, a series of 17 repeated acoustic trawl surveys within a ca. 1500 km2 area covering the major spawning location for Norwegian spring-spawning herring (Clupea harengus) was conducted over a period of about 1 month. Local herring abundance increased from ca. 25 000 to 237 000 t, a significant proportion of the total spawning stock, in just 3 d and subsequently decreased to <30 000 t over the next 7 d. The abundance change was due to a single major spawning wave developing over the observation period, and an estimated 46 000 t of eggs and milt were deposited during the short time spent at the spawning ground. There was no difference in spawning activity between day and night, but herring were more associated with deep trenches and also generally stayed deeper in more dense schools during daylight than night-time. Schooling behaviour and distribution were also strongly state-dependent, and both school swimming depth and school height decreased as spawning progressed, as did the bottom depth where the schools were located. The massive herring spawning events seem to be low-risk adaptations to an environment where predators are abundant, with rapid spawning in huge aggregations as a strategy for predator swamping.