Calibrating accelerometer tags with oxygen consumption rate of rainbow trout (Oncorhynchus mykiss) and their use in aquaculture facility: A case study

SIMPLE SUMMARY: Measuring metabolic rates in free-swimming fish would provide valuable insights about the energetic costs of different life activities this is challenging to implement in the field due to the difficulty of performing such measurements. Thus, the calibration of acoustic transmitters with the oxygen consumption rate (MO(2)) could be promising to counter the limitations observed in the field. In this study, calibrations were performed in rainbow trout (Oncorhynchus mykiss), and a subsample of fish was implanted with such a transmitter and then followed under aquaculture conditions. The use of acoustic transmitters calibrated with MO(2) appeared to be a promising tool to estimate energetic costs in free-swimming rainbow trout, and for welfare assessment in the aquaculture industry. ABSTRACT: Metabolic rates are linked to the energetic costs of different activities of an animal’s life. However, measuring the metabolic rate in free-swimming fish remains challenging due to the lack of possibilities to perform these direct measurements in the field. Thus, the calibration of acoustic transmitters with the oxygen consumption rate (MO(2)) could be promising to counter these limitations. In this study, rainbow trout (Oncorhynchus mykiss Walbaum, 1792; n = 40) were challenged in a critical swimming test (U(crit)) to (1) obtain insights about the aerobic and anaerobic metabolism throughout electromyograms; and (2) calibrate acoustic transmitters’ signal with the MO(2) to be later used as a proxy of energetic costs. After this calibration, the fish (n = 12) were implanted with the transmitter and were followed during ~50 days in an aquaculture facility, as a case study, to evaluate the potential of such calibration. Accelerometer data gathered from tags over a long time period were converted to estimate the MO(2). The MO(2) values indicated that all fish were reared under conditions that did not impact their health and welfare. In addition, a diurnal pattern with higher MO(2) was observed for the majority of implanted trout. In conclusion, this study provides (1) biological information about the muscular activation pattern of both red and white muscle; and (2) useful tools to estimate the energetic costs in free-ranging rainbow trout. The use of acoustic transmitters calibrated with MO(2), as a proxy of energy expenditure, could be promising for welfare assessment in the aquaculture industry

Assessing thornback ray growth pattern in different areas of Western-Central Mediterranean Sea through a Multi-Model Inference analysis

The lack of information on age validation often affects ageing studies in cartilaginous fish, even in the most common species. Recently, the annual growth band deposition pattern has been directly validated for thornback ray in the Mediterranean Basin, thus providing a highly reliable protocol for age reading. In this regard, taking advantage of this new information, the present study aims to investigate this species growth for the first time over a wide area of the Western and Central Mediterranean Sea, involving four different FAO geographic sub-areas. In order to provide an accurate description of the species growth, different models were fitted to the age-length data obtained from the observation of vertebral centra thin sections. A total of 720 specimens were analysed (358 females and 362 males) with total length ranging between 11.5 and 86.4 cm. The corrected Akaike's Information criterion (AICc) indicated, among the tested models, the three-parameter von Bertalanffy function as the most robust in describing the species growth. Growth modelling outcomes revealed the thornback rays as capable of growing relatively fast during the first years; the growth rate gradually slows down allowing maximum sizes of about 90–100 cm in total length to be reached. Significant discrepancies in the growth pattern were found between sexes in all investigated areas with the only exception being in the Northern Tyrrhenian Sea. Differences in growth patterns were observed between areas, specifically in the estimated growth rate of the species for each sub-region. The present study, confirmed the importance of the availability of a validated ageing protocol and testing multiple growth models. Moreover, our results highlighted the urgent need to investigate a species growth in a wide geographic area, searching also for possible differences at sub-region level. Providing this information could indeed allow eventual management plans to be adapted to the exact growth pattern that the species exhibit in the region, in this way increasing their effectiveness

Behavioural indicators of welfare in farmed fish

Behaviour represents a reaction to the environment as fish perceive it and is therefore a key element of fish welfare. This review summarises the main findings on how behavioural changes have been used to assess welfare in farmed fish, using both functional and feeling-based approaches. Changes in foraging behaviour, ventilatory activity, aggression, individual and group swimming behaviour, stereotypic and abnormal behaviour have been linked with acute and chronic stressors in aquaculture and can therefore be regarded as likely indicators of poor welfare. On the contrary, measurements of exploratory behaviour, feed anticipatory activity and reward-related operant behaviour are beginning to be considered as indicators of positive emotions and welfare in fish. Despite the lack of scientific agreement about the existence of sentience in fish, the possibility that they are capable of both positive and negative emotions may contribute to the development of new strategies (e. g. environmental enrichment) to promote good welfare. Numerous studies that use behavioural indicators of welfare show that behavioural changes can be interpreted as either good or poor welfare depending on the fish species. It is therefore essential to understand the species-specific biology before drawing any conclusions in relation to welfare. In addition, different individuals within the same species may exhibit divergent coping strategies towards stressors, and what is tolerated by some individuals may be detrimental to others. Therefore, the assessment of welfare in a few individuals may not represent the average welfare of a group and vice versa. This underlines the need to develop on-farm, operational behavioural welfare indicators that can be easily used to assess not only the individual welfare but also the welfare of the whole group (e. g. spatial distribution). With the ongoing development of video technology and image processing, the on-farm surveillance of behaviour may in the near future represent a low-cost, noninvasive tool to assess the welfare of farmed fish.Fundação para a Ciência e Tecnologia, Portugal [SFRH/BPD/42015/2007]info:eu-repo/semantics/publishedVersio

Surgical implantation of electronic tags does not induce medium-term effect: Insights from growth and stress physiological profile in two marine fish species

Background: Telemetry applied to aquatic organisms has recently developed greatly. Physiological sensors have been increasingly used as tools for fish welfare monitoring. However, for the technology to be used as a reliable welfare indicator, it is important that the tagging procedure does not disrupt fish physiology, behaviour and performance. In this communication, we share our medium-term data on stress physiological profile and growth performance after surgical tag implantation in two important marine fish species for European aquaculture, the sea bream (Sparus aurata) and the European sea bass (Dicentrarchus labrax). Results: Blood samples after surgical tag implantation (46 days for the sea bream and 95 days for the sea bass) revealed no differences between tagged and untagged fish in cortisol, glucose and lactate levels, suggesting that the tag implantation does not induce prolonged stress in these species. Moreover, the specific growth rates were similar in the tagged and untagged fish of both species. Conclusion: Surgical tag implantation does not have medium-term consequences for the stress physiology and growth performance of these two marine fish species in a controlled environment. These observations support the use of accelerometer tags as valuable tools for welfare monitoring in aquaculture conditions. This study also shows that tagged fish can be sampled during experiments and considered a representative portion of the population, as they display growth and physiological parameters comparable to those of untagged fish

Residui di metalli pesanti (Zn, Cu, Hg, Cd) nel tessuto muscolare di Anguilla anguilla: valutazione del rischio tossicologico per il consumatore.

In the present survey, metal residues (Zn, Cu, Hg and Cd,) were determined in the muscle of Anguilla anguilla in order to evaluate the risk for human deriving from the consumption of this species. Zinc showed the highest concentrations, (mean: 18.20 μg g-1) followed by copper (mean: 0.48 μg g-1), mercury (mean: 0.15 μg g-1) and cadmium (mean: 0.04 μg g-1). None of the fish samples analysed presented metal concentrations exceeding the limits fixed by the legislation. To asses the potential health impact, the estimated weekly intake was calculated. The estimated weekly intake (Hg: 1.05 μg kg-1 b.w.; Cd: 0.28 μg kg-1 b.w.) was far above the established Provisional Tolerable Weekly Intake for this species

Spatial distribution of marine macro-litter on the seafloor in the northern Mediterranean Sea: the MEDITS initiative

Marine litter is one of the main sources of anthropogenic pollution in the marine ecosystem, with plastic representing a global threat. This paper aims to assess the spatial distribution of plastic macro-litter on the seafloor, identifying accumulation hotspots at a northern Mediterranean scale. Density indices (items km–2) from the MEDITS trawl surveys (years 2013-2015) were modelled by generalized additive models using a Delta-type approach and several covariates: latitude, longitude, depth, seafloor slope, surface oceanographic currents and distances from main ports. To set thresholds for the identification of accumulation areas, the percentiles (85th, 90th and 95th) of the plastic spatial density distribution were computed on the raster data. In the northern Mediterranean marine macro-litter was widespread (90.13% of the 1279 surveyed stations), with plastic by far the most recurrent category. The prediction map of the plastic density highlighted accumulation areas (85th, 90th and 95th percentiles of the distribution, respectively, corresponding to 147, 196 and 316 items km–2) in the Gulf of Lions, eastern Corsica, the eastern Adriatic Sea, the Argo-Saronic region and waters around southern Cyprus. Maximum densities were predicted in correspondence to the shallower depths and in proximity to populated areas (distance from the ports). Surface currents and local water circulation with cyclonic and anticyclonic eddies were identified as drivers likely facilitating the sinking to the bottoms of floating debrisS

New insight into the toxic effects of lithium in the ragworm Perinereis cultrifera as revealed by lipidomic biomarkers, redox status, and histopathological features

Lithium (Li) is a toxic monovalent alkaline metal used in household items common to industrial applications. The present work was aimed at investigating the potential toxic effects of LiCl on the redox status, fatty acid composition, and histological aspects of the marine ragworm Perinereis cultrifera. Sea worms were exposed to LiCl graded doses (20, 40, and 80 mg/L) for 48 h. Compared with the control group, the saturated fatty acids (SFA) decreased while monounsaturated (MUFA) and polyunsaturated fatty acids (PUFA) increased upon exposure to LiCl. The increase in PUFA n-3 and PUFA n-6 was concomitant to an increase in docosahexaenoic (DHA: C22:6n-3), eicosapentaenoic (EPA: C20:5n-3), and docosapentaenoic acid (C22:5n-6) fatty acids. Results showed that LiCl-treated specimens accumulate lithium with increasing exposure gradient. Indeed, the exposure to LiCl doses promoted oxidative stress with an increase of the ferric reducing antioxidant power (FRAP), malondialdehyde (MDA), hydrogen peroxide (H2O2), advanced oxidation protein product (AOPP), and protein carbonyl (PCO) as well as the enzymatic and non-enzymatic antioxidants (non-protein thiols (NPSH), catalase (CAT), superoxide dismutase (SOD), reduced glutathione (GSH), glutathione peroxidase (GPx), glutathione S-transferase (GST), and metallothionein (MT)) levels in all treated groups. Our biochemical findings have been affirmed by the histopathological observations showing hyperplasia and loss of the intestine structure in treated specimens. Overall, our findings give new insights on the toxic effect of LiCl on the redox status of P. cultrifera body tissue and highlighted the usefulness of the FA composition as an early sensitive bioindicators to better understand LiCl mechanism of toxicity in marine polychaetes

Assessment of the effects of captivity on first sexual maturity of wild-caught and hatchery produced mullet (Mugil cephalus)

INTRODUCTION In fish, puberty is susceptible to multiple, interacting environmental cues. As a result, farming conditions may have varying influences on the age of first sexual maturity, causing precocious puberty in some species or delayed and even completely blocked puberty in others. Therefore, this study aimed at characterizing pubertal development in grey mullet (Mugil cephalus), an important fish candidate for domestication and aquaculture production. MATERIALS AND METHODS Two stocks of grey mullet were compared: wild-caught (WC; Apulia, Italy) and hatchery produced (HP; National Center for Mariculture, Eilat, Israel) grey mullet, both subjected to captive conditions consist of ambient seawater salinity (40 ppt; Gulf of Eilat, Red Sea) and photo-thermal regime. The age of the fish was estimated based on their scales. Growth performance and gonadal development were monitored in 2- and 3- year old fish (2y and 3y). RESULTS AND CONCLUSIONS Our results revealed that all 2y fish had immature gonads. The majority of 2y females exhibited late perinucleolar oocytes as the most advanced oocyte stage. Yet, HP females had significantly larger oocytes than WC specimens. Testis from an immature age 2y HP specimen showed small seminiferous lobules. Only spermatogonia, along with somatic cells were visible. Gonad section from a 2y HP intersex showed the presence of all stages of spermatogenesis. Scattered perinucleolar stage oocytes were visible, indicating that both WC and HP, had immature testes. Following 3y age category revealed that WC females were larger than cognate males. Although not significant, the HP mullets appear to exhibit a similar trend. Gonadosomatic index (GSI) values in 3y HP females and males were significantly higher than those of the WC of the same age. Undifferentiated gonads were found in 20% of WC fish compared to 5% in the HP fish. While only 33% had reached vitellogenic oocytes level, 54% of the HP females reached this level of development. Males exhibited a significant difference in development: 100% of the WC males showed first stages of spermatogenesis, while 67% of the male population in the HP group produced mature sperm. HP females, sampled during natural spawning season, reached maturity and ovulation. Their GSI exceeded 15%. Interestingly, approximately 50% of the HP females’ GSI exhibited markedly developed gonads with GSI values ranging between 10-20% while all the others were lagging far behind, having GSI values between 0.2 to 0.3 %. GSI values in WC females were also divided into 2 sub groups and found to be significantly lower than those of the hatchery produced females (1-6% and <1% respectively). Males also exhibited two GSI groups pattern, higher GSI values were exhibited by HP fish (1.5%-2.75% and <1% compared to 0.2-0.5% and <0.15%). Suggesting hierarchy plays a major role affecting gonadal development in mullets. In summary, the 3 yr old HP mullet females and males exhibited enhanced gonadal maturation as compared to that of the WC captive-reared fish, probably as a result of domestication. The project received funding from the European Union 7FP (GA 603121, DIVERSIFY)