Smart biosensing device for tracking fish behaviour

Biosensor technology for tracking individual challenged fish behaviour has the potential to revolutionize aquaculture, allowing farmers and breeders to orientate selective breeding towards more robust and efficient fish or improve culture conditions for a more sustainable and ethical production. The proposed solution within the AQUAEXCEL2020 EU project is a stand-alone, small and light (1 g) device (AEFishBIT), based on a tri-axial accelerometer and a microprocessor. It is externally attached to the operculum to monitor physical activity by mapping accelerations in x- and y-axes, while operculum beats (z-axis) serve as a measurement of respiratory frequency. The conducted operculum attachment protocol does not show signs of tissue damage or growth impairment in active feeding gilthead sea bream. AEFishBIT offers a wide range of new information based on individual behaviour, allowing to point out the asynchrony of movements as an indirect measure of aging and adaptability to farming environment, as well as to discriminate different coping behaviour (proactive or reactive) of gilthead sea bream challenged with low water oxygen concentrations. AEFishBIT also provides reliable information of disease outcome in fish parasitized with an intestinal myxozoan, emerging as a powerful tool for sensing the quality of the environment and improving selective breeding protocols.The study has received funding from the European Union’s Horizon 2020 research and innovation programme, GA no 652831 (AQUAEXCEL2020)

Selection for growth is associated in gilthead sea bream (Sparus aurata) with diet flexibility, changes in growth patterns and higher intestine plasticity

Farmed gilthead sea bream (Sparus aurata) is able to grow efficiently with new feed formulations based on plant ingredients. Here, two experimental diets with standard and high inclusion levels of plant ingredients were formulated to assess the suited use of plant-based diets in fish with different growth genetic backgrounds. To pursue this issue, a long-term feeding trial (12-months) was conducted with fish (17 g initial body weight) of 16 families coming from the broodstock of PROGENSA project, that were grown communally in the IATS-CSIC experimental facilities. All fish in the study (2545) were PIT-tagged, and their pedigree was re-constructed with 96% success by using a SMsa1 multiplex of 11 microsatellites, which revealed the main parents contributions of 5 females and 6 males. Each diet was randomly assigned to replicate 3000 L tanks, gathering each replicate a similar family composition through all the feeding trial. Data on growth performance highlighted a strong ge- netic effect on growth trajectories, associated with enhanced growth during winter in fish selected for faster growth. No main dietary effects were found on growth rates or condition factor, and regression-correlation analyses of growth rates across families on both diets suggest that genome by diet interaction was weak, while genetic variation accounted for most of the growth phenotypic variation. Hepatosomatic index (HSI) and me- senteric fat index (MSI) of five families, covering the growth variability of the population, were regulated nu- tritionally and genetically, but without statistically significant genome by diet interactions. Fish from faster growing families showed shorter intestines after being fed the control diet, but this phenotype was masked by the enriched plant-based diet. Collectively, the results demonstrate that selection for faster growth is associated in gilthead sea bream with different growth trajectories and a high diet flexibility and intestine plasticity.Versión del editor2,04

Recent advances in the crosstalk between adipose, muscle and bone tissues in fish

Control of tissue metabolism and growth involves interactions between organs, tissues, and cell types, mediated by cytokines or direct communication through cellular exchanges. Indeed, over the past decades, many peptides produced by adipose tissue, skeletal muscle and bone named adipokines, myokines and osteokines respectively, have been identified in mammals playing key roles in organ/tissue development and function. Some of them are released into the circulation acting as classical hormones, but they can also act locally showing autocrine/paracrine effects. In recent years, some of these cytokines have been identified in fish models of biomedical or agronomic interest. In this review, we will present their state of the art focusing on local actions and inter-tissue effects. Adipokines reported in fish adipocytes include adiponectin and leptin among others. We will focus on their structure characteristics, gene expression, receptors, and effects, in the adipose tissue itself, mainly regulating cell differentiation and metabolism, but in muscle and bone as target tissues too. Moreover, lipid metabolites, named lipokines, can also act as signaling molecules regulating metabolic homeostasis. Regarding myokines, the best documented in fish are myostatin and the insulin-like growth factors. This review summarizes their characteristics at a molecular level, and describes both, autocrine effects and interactions with adipose tissue and bone. Nonetheless, our understanding of the functions and mechanisms of action of many of these cytokines is still largely incomplete in fish, especially concerning osteokines (i.e., osteocalcin), whose potential cross talking roles remain to be elucidated. Furthermore, by using selective breeding or genetic tools, the formation of a specific tissue can be altered, highlighting the consequences on other tissues, and allowing the identification of communication signals. The specific effects of identified cytokines validated through in vitro models or in vivo trials will be described. Moreover, future scientific fronts (i.e., exosomes) and tools (i.e., co-cultures, organoids) for a better understanding of inter-organ crosstalk in fish will also be presented. As a final consideration, further identification of molecules involved in inter-tissue communication will open new avenues of knowledge in the control of fish homeostasis, as well as possible strategies to be applied in aquaculture or biomedicine

Effects of genetics and early life mild hypoxia on individual growth and size variation in gilthead sea bream (Sparus aurata)

The present study evaluated, in an 18-month gilthead sea bream trial, the time course effects of genetics on individual size variation and growth compensation processes in the offspring of families selected by growth in the PROGENSA breeding program. Families categorized as fast, intermediate and slow growing had different growth trajectories with a more continuous growth in fast growth families. This feature was coincident with a reduced size variation at the beginning of the trial that clustered together the half-sib families sharing the same father. Correlation analysis evidenced that the magnitude of compensatory growth was proportional to the initial size variation with no rescaling of families at this stage. By contrast, the finishing growth depensation process can mask, at least partially, the previous family convergence. This reflects the different contribution across the production cycle of genetics and environmental factors in growth, production and welfare. How early life experiences affect growth compensatory at juvenile stages was also evaluated in a separate cohort, and intriguingly, a first mild-hypoxia pulse at 60-81 days posthatching (dph) increased survival rates by 10% preventing growth impairment when fish were exposed to a second hypoxia episode (112-127 dph). The early hypoxia experience did not have a negative impact on growth compensatory processes at juvenile stages. By contrast, a diminished capacity for growth compensation was found with repeated or late hypoxia experiences. All this reinforces the use of size variation as a main criterion for improving intensive fish farming or selective breeding into practice.This work was supported by the project Bream-AquaINTECH: From Nutrition and Genetics to Sea Bream Aquaculture Intensification and Technological Innovation, RTI2018-094128-B-I00. Additional funding was received from the EU project PerformFISH (Integrating Innovative Approaches for Competitive and Sustainable Performance across the Mediterranean Aquaculture Value Chain) (H2020-SFS-2016-2017; 727610). This publication reflects the views only of the authors, and the European Commission cannot be held responsible for any use which may be made of the information contained therein. PSM contract was funded by EU project PerformFISH. EP was founded by a Postdoctoral Research Fellow (Juan de la Cierva-Incorporación, Reference IJCI-2016-27637) from MINECON

Changes in transcriptomic and behavioural traits in activity and ventilation rates associated with divergent individual feed efficiency in gilthead sea bream (Sparus aurata)

Feed conversion ratio (FCR) is an important trait to target in fish breeding programs, and the aim of the present study is to underline how the genetic improvement of FCR in gilthead sea bream (Sparus aurata) drives to changes in transcriptional and behavioural patterns. Groups of fish with high (FCR+) and low (FCR-) individual FCR were established at the juvenile stage (161–315 dph) by rearing isolated fish on a restricted ration. Fish were then grouped on the basis of their individual FCR and they grew up until behavioural monitoring and gene expression analyses were done at 420 dph. The AEFishBIT datalogger (externally attached to operculum) was used for simultaneous measurements of physical activity and ventilation rates. This allowed discrimination of FCR+ and FCR- groups according to their different behaviour and energy partitioning for growth and locomotor activity. Gene expression profiling of liver and white muscle was made using customized PCR-arrays of 44 and 29 genes, respectively. Up to 15 genes were differentially expressed in liver and muscle tissues highlighting a different metabolic scope of FCR+ and FCR- fish. Hepatic gene expression profile of FCR- fish displayed a lower lipogenic activity that was concurrent with a down-regulation of markers of mitochondrial activity and oxidative stress, as well as a reallocation of body fat depots with an enhanced flux of lipids towards skeletal muscle. Muscle gene expression profile of FCR- fish matched with stimulatory and inhibitory growth signals, and an activation of energy sensors and antioxidant defence as part of the operating mechanisms for a more efficient muscle growth. These new insights contribute to phenotype the genetically mediated differences in fish FCR thanks to the combination of transcriptomic and behavioural approaches that contribute to better understand the mechanisms involved in a reliable FCR improvement of farmed gilthead sea bream

From operculum and body tail movements to different coupling of physical activity and respiratory frequency in farmed gilthead sea bream and European sea bass. Insights on aquaculture biosensing

The AEFishBIT tri-axial accelerometer was externally attached to the operculum to assess the divergent activity and respiratory patterns of two marine farmed fish, the gilthead sea bream (Sparus aurata) and European sea bass (Dicentrarchus labrax). Analysis of raw data from exercised fish highlighted the large amplitude of operculum aperture and body tail movements in European sea bass, which were overall more stable at low-medium exercise intensity levels. Cosinor analysis in free-swimming fish (on-board data processing) highlighted a pronounced daily rhythmicity of locomotor activity and respiratory frequency in both gilthead sea bream and European sea bass. Acrophases of activity and respiration were coupled in gilthead sea bream, acting feeding time (once daily at 11:00 h) as a main synchronizing factor. By contrast, locomotor activity and respiratory frequency were out of phase in European sea bass with activity acrophase on early morning and respiration acrophase on the afternoon. The daily range of activity and respiration variation was also higher in European sea bass, probably as part of the adaptation of this fish species to act as a fast swimming predator. In any case, lower locomotor activity and enhanced respiration were associated with larger body weight in both fish species. This agrees with the notion that selection for fast growth in farming conditions is accompanied by a lower activity profile, which may favor an efficient feed conversion for growth purposes. Therefore, the use of behavioral monitoring is becoming a reliable and large-scale promising tool for selecting more efficient farmed fish, allowing researchers and farmers to establish stricter criteria of welfare for more sustainable and ethical fish production.European Union’s Horizon 2020 Research and Innovation Programme under grant agreement No. 652831 (AQUAEXCEL2020, Aquaculture infrastructures for excellence in European fish research towards 2020).ProID2017010062, from Canarian Agency for Research, Innovation and Information Society (Gobierno de Canarias), co-funded with European Structural and Investment Funds (2014-2020)FICASES, Fish Cage Sensor System (TEC2017-89403-C2-2-R) from Spanish Ministry of Economy, Industry and Competitiveness, co-funded with European Regional Development Funds (2014-2020).Peer reviewe

Use of accelerometer technology for individual tracking of activity patterns, metabolic rates and welfare in farmed gilthead sea bream (Sparus aurata) facing a wide range of stressors

The biosensor technology has the potential to revolutionize the aquaculture industry, but the selection of tagging method, operational mode (stand-alone vs. wireless systems) and telemetry technology ultimately depends on living species, life stage and research question. In particular, AEFishBIT is a small and stand-alone device composed of a tri-axial accelerometer, a microprocessor, a battery, and a RFID tag that was designed to be externally attached to the operculum. This unique location serves to provide simultaneous measurements of activity patterns (signals of x- and y-axes) and respiratory frequency (z-axis signal) processed by on-board algorithms. The validity of measurements was initially proved in exercised fish in a swim tunnel respirometer, and its use as a reliable tool for the individual monitoring of whole-organism traits in free-swimming gilthead sea bream was tested then in fish facing a wide range of biotic and abiotic stressors. The impact of the tagging method, based on the use of monel piercing fish tags with a flexible heat shrink polyethylene ring, was also evaluated and no signs of growth impairment, operculum damage or gill lamellae haemorrhage were found 10 days post-tagging. The autonomy of the device was 6 hours of continuous recording with re-programmable lag times and recording schedules of 2 min windows at regular intervals along the experimental period (2-8 days). Such procedure underlined a negative linear correlation between fasting weight loss and operculum breaths, becoming respiratory frequency a reliable indicator of basal metabolic rates. Biosensing signals also highlighted the more continuous physical activity and increased respiratory rates of young fish when comparisons were made between one- and three-year old fish. Also, AEFishBIT measurements evidenced a generalized increase of respiratory frequency during severe hypoxia (2-3 ppm), but the individuals classified as proactive fish also shared an increased physical activity for supporting escape reactions in a milieu with low oxygen availability. Likewise, we also observed an overall increase of physical activity with the decrease of tank space availability, which can contribute to establish stricter criteria of welfare in farmed fish. Finally, the reduction of respiratory frequency was a consistent diagnostic marker of the progression of parasitic enteritis in experimentally infected fish with the myxozoan Enteromyxum leei. Altogether, this work constitutes the proof of concept of the use of biosensor technology as a reliable tool for individual fish phenotyping of whole-organism traits in farmed fish, contributing to improve animal welfare and productivity of aquaculture industry.European Union’s Horizon 2020 Research and Innovation Programme under grant agreement No. 652831 (AQUAEXCEL2020, Aquaculture infrastructures for excellence in European fish research towards 2020).Ramón y Cajal Postdoctoral Research Fellowship RYC2018-024049-I/AEI/10.13039/501100011033Peer reviewe

Intelligent smart device for tracking fish behaviour

Trabajo presentado en el XII Conference of the Iberian Association for Comparative Endocrinology (AIEC), celebrado en Faro (Portugal), del 26 al 28 de septiembre de 2019With the use of electronic tracking technology, data on fish movements, physiology and environmental parameters can be collected from each tagged individual. The perfect tag - small size, lasting activity, long distance data transmission (e.g. radiotransmitters, acoustic transmitters, pop-up satellite archival tags) - does not exist, and the choice of telemetry technology and tagging method (external, intracelomic, intragastric) depends on fish species, life stage and research question. The proposed solution within the AQUAEXCEL2020 EU project is a stand-alone, small and light (1 g) device (AEFishBIT), composed of a tri-axial accelerometer, a microprocessor, a battery and an RFID tag for quick-smart identification. The device is externally attached to the operculum to monitor physical activity by mapping accelerations in x- and y-axes, while operculum beats (z-axis) serve as a measurement of respiratory frequency. Initial functional validation has been made with gilthead sea bream and European sea bass juveniles in swimming test chambers, highlighting a high correlation of oxygen consumption and swimming activity with the calculated AEFishBIT records (MartosSitcha et al., 2019; Frontiers in Physiology 10:667). Current studies with free-swimming fish reveal that the attachment protocol does not have a negative impact on growth performance in active feeding fish, offering a wide range of new information based on individual behaviour: i) the switch from nocturnal to diurnal rhythms of activity across season, ii) the different energy partitioning for growth and maintenance, iii) the asynchrony of movements as an indirect measure of aging and adaptability to culture environment, and iv) the different coping behaviour of fish challenged with low water oxygen concentrations. AEFishBIT also provides reliable information of disease outcome in fish parasitized with the intestinal myxozoan Enteromyxum leei, emerging as the ideal complement for sensing the quality of the environment and improving selective breeding protocols.AQUAEXCEL2020 EU Project, GA 65283

Selection for growth is associated in gilthead sea bream (Sparus aurata) with diet flexibility, changes in growth patterns and higher intestine plasticity

Farmed gilthead sea bream (Sparus aurata) is able to grow efficiently with new feed formulations based on plant ingredients. Here, two experimental diets with standard and high inclusion levels of plant ingredients were formulated to assess the suited use of plant-based diets in fish with different growth genetic backgrounds. To pursue this issue, a long-term feeding trial (12-months) was conducted with fish (17 g initial body weight) of 16 families coming from the broodstock of PROGENSA project, that were grown communally in the IATS-CSIC experimental facilities. All fish in the study (2545) were PIT-tagged, and their pedigree was re-constructed with 96% success by using a SMsa1 multiplex of 11 microsatellites, which revealed the main parents contributions of 5 females and 6 males. Each diet was randomly assigned to replicate 3000 L tanks, gathering each replicate a similar family composition through all the feeding trial. Data on growth performance highlighted a strong genetic effect on growth trajectories, associated with enhanced growth during winter in fish selected for faster growth. No main dietary effects were found on growth rates or condition factor, and regression-correlation analyses of growth rates across families on both diets suggest that genome by diet interaction was weak, while genetic variation accounted for most of the growth phenotypic variation. Hepatosomatic index (HSI) and mesenteric fat index (MSI) of five families, covering the growth variability of the population, were regulated nutritionally and genetically, but without statistically significant genome by diet interactions. Fish from faster growing families showed shorter intestines after being fed the control diet, but this phenotype was masked by the enriched plant-based diet. Collectively, the results demonstrate that selection for faster growth is associated in gilthead sea bream with different growth trajectories and a high diet flexibility and intestine plasticity