Biological and Ethological Response of Black Sea Golden Grey Mullet (Chelon auratus Risso, 1810) Fries to Different Salinities and Temperatures

The aim of this paper was to investigate the biological and ethological response of golden grey mullet Chelon auratus (Risso, 1810) fries collected from Romanian Black Sea shallow waters to different salinities and temperatures, in order to document the optimal conditions for controlled rearing. The species’ potential for aquaculture is enhanced by its eurihalyne and eurithermal adaptability, allowing it to grow in a variety of ecosystems, including the Romanian Black Sea area, with its highly variable salinity and temperature specificities. Three experimental set-ups were designed: a salinity tolerance test, with 5 salinity regimes (0.3‰, 5‰, 10‰, 15‰ and 20‰), a temperature tolerance experiment, involving both temperature decrease (down to 8°C) and increase (up to 34°C), and an extreme salinity test, reaching a maximum value of 95‰. The aggregated results obtained from the three experiments indicated that golden grey mullet fries can indeed tolerate a wide range of temperatures (8°C - 36°C) and salinities (5‰-70‰), with the optimal range between 10‰ and 30‰ salinity, at temperatures of 10°C - 25°C. The practical purpose of this investigation was supporting the diversification of local mariculture species, as mullets can be excellent candidates for the enhancement of aquaculture in the area.

Effect of Different Routes of Vaccination against Aeromonas salmonicida on Rearing Indicators and Survival after an Experimental Challenge of Pikeperch (Sander lucioperca) in Controlled Rearing

Bacterial diseases are a significant problem in the controlled rearing of fish. Furunculosis (Aeromonas sp.), flavobacteriosis (Flavobacterium sp.), and pseudomonadosis (Pseudomonas sp.) are currently the most frequently identified diseases in recirculating aquaculture systems of various fish species. Such a situation is also observed in pikeperch rearing. Due to the emerging difficulties of effective prophylaxis using commercial vaccines, interest in the use of autovaccinations is increasing, not only in ichthyopathology but also in other veterinary fields. Our research aimed to assess the effect of the vaccination method on the overall condition of the fish and survival after the experimental infection with Aeromonas salmonicida. Pikeperch were vaccinated by (1) bath, (2) a single i.p. injection, or (3) feed. The fish were measured and weighed on day 0 and after 28 and 56 days of the experiment. Specific growth rate, daily growth rate, condition factor, and feed conversion ratio were calculated. On days 7, 14, 21, and 28 of the experiment, ceruloplasmin and lysozyme levels were rated. In addition, a challenge test was performed. The obtained results showed that the method of vaccination is important and affects the growth of fish, the overall condition of fish, and survival after experimental infection.

Using automation to combat the replication crisis: A case study from controlled-rearing studies of newborn chicks

The accuracy of science depends on the precision of its methods. When fields produce precise measurements, the scientific method can generate remarkable gains in knowledge. When fields produce noisy measurements, however, the scientific method is not guaranteed to work—in fact, noisy measurements are now regarded as a leading cause of the replication crisis in psychology. Scientists should therefore strive to improve the precision of their methods, especially in fields with noisy measurements. Here, we show that automation can reduce measurement error by ~60% in one domain of developmental psychology: controlled-rearing studies of newborn chicks. Automated studies produce measurements that are 3-4 times more precise than non-automated studies and produce effect sizes that are 3-4 times larger than non-automated studies. Automation also eliminates experimenter bias and allows replications to be performed quickly and easily. We suggest that automation can be a powerful tool for improving measurement precision, producing high powered experiments, and combating the replication crisis.

Atlantic bluefin tuna spawn at suboptimal temperatures for their offspring

Life-history traits such as spawning migrations and timing of reproduction are adaptations to specific environmental constraints and seasonal cycles in many organisms' annual routines. In this study we analyse how offspring fitness constrains spawning phenology in a large migratory apex predator, the Atlantic bluefin tuna. The reproductive schedule of Atlantic bluefin tuna varies between spawning sites, suggesting plasticity to local environmental conditions. Generally, temperature is considered to be the main constraint on tuna spawning phenology. We combine evidence from long-term field data, temperature-controlled rearing experiments on eggs and larvae, and a model of egg fitness, and show that Atlantic bluefin tuna do not spawn to optimize egg and larval temperature exposure. The timing of spawning leads to temperature exposure considerably lower than optimal at all spawning grounds across the Atlantic Ocean. The early spawning is constrained by thermal inhibition of egg hatching and larval growth rates, but some other factors must prevent later spawning. Matching offspring with ocean productivity and the prey peak might be an important driver for bluefin tuna spawning phenology. This finding is important for predictions of reproductive timing in future climate warming scenarios for bluefin tuna.

Spontaneous Preference for Slowly Moving Objects in Visually Naïve Animals

To perceive the world successfully, newborns need certain types of visual experiences. The development of object recognition, for example, requires visual experience with slowly moving objects. To date, however, it is unknown whether newborns actively seek out the best visual experiences for developing object recognition. To address this question, I used an automated controlled-rearing method to examine whether visually naïve animals (newborn chicks) seek out slowly moving objects. Despite receiving equal exposure to slowly and to quickly rotating objects, the majority of the chicks developed a preference for slowly rotating objects. This preference was robust, producing large effect sizes across objects, experiments, and successive test days. These results indicate that newborn brains rapidly develop mechanisms for orienting young animals toward optimal visual experiences, thus facilitating the development of object recognition. This study also demonstrates that automation can be a valuable tool for studying the origins and development of visual preferences.

The development of newborn object recognition in fast and slow visual worlds

Object recognition is central to perception and cognition. Yet relatively little is known about the environmental factors that cause invariant object recognition to emerge in the newborn brain. Is this ability a hardwired property of vision? Or does the development of invariant object recognition require experience with a particular kind of visual environment? Here, we used a high-throughput controlled-rearing method to examine whether newborn chicks ( Gallus gallus ) require visual experience with slowly changing objects to develop invariant object recognition abilities. When newborn chicks were raised with a slowly rotating virtual object, the chicks built invariant object representations that generalized across novel viewpoints and rotation speeds. In contrast, when newborn chicks were raised with a virtual object that rotated more quickly, the chicks built viewpoint-specific object representations that failed to generalize to novel viewpoints and rotation speeds. Moreover, there was a direct relationship between the speed of the object and the amount of invariance in the chick's object representation. Thus, visual experience with slowly changing objects plays a critical role in the development of invariant object recognition. These results indicate that invariant object recognition is not a hardwired property of vision, but is learned rapidly when newborns encounter a slowly changing visual world.

Bacterial and parasitic factors diagnosed in eel farmed in Poland in the years 2010-2014

European eel Anguilla anguilla L. is a fish species highly valued in European fisheries, currently reared under controlled conditions (Aquatic Recirculation System - RAS). In order to protect the health of fish, regular check-ups are carried out in specialized veterinary laboratories. Health hazards are recognized on the basis of clinical, pathological, microbiological, and parasitological surveys. The aim of the study was to analyze the results of health assessment of eels reared under controlled conditions, which was performed in the Diagnostics Laboratory of Fish and Crayfish Diseases, Department of Veterinary Hygiene, Voivodeship Veterinary Inspectorate in Olsztyn, in the period from 2010 to 2014. The results are presented according to the etiologic agents, divided into bacterial and parasitic diseases. In this period, 73 samples (100%) were examined, including 5 samples (6.85%) from glass eels and 68 (93.15%) from elvers. Microorganisms isolated from the collected material were mainly conditionally pathogenic, such as Pseudomonas fluorescens, Aeromonas hydrophila, Shewanella putrefaciens, Aeromonas sobria, Flavobacterium spp., and Chryseobacterium indologenes. The parasitological examination revealed infection with Trichodina spp., Ichthyophtirius multiphilliis, and Pseudodactylogyrus spp. The most frequently diagnosed were gill monogeneans, detected in 34 cases (75.55% of all positive parasitological test results). In 21 cases (61.8%) the infestation manifested itself as a disease. The remaining 13 cases were asymptomatic carriers (38.2%). The analysis shows that the main problem in the controlled rearing of eel are parasitic infestations, which may be endemic and pose a constant threat. Systematic monitoring and preventive measures are necessary throughout the rearing and fattening of fry to maintain a good health status of eels.