Patent Description:
A device for monitoring physical activity and breathing frequency in fish is described. The device is configured to be installed in the fish's operculum (or gill cover of the fish), and by means of an acceleration sensor, to record the accelerations thereof in the plane of the gill cover and in the normal direction thereof to said plane.

The method for monitoring the accelerations of the gill cover enables the breathing frequency of the fish and the movements resulting from the swimming activity to be extracted, jointly and simultaneously, in order to determine the metabolic state and well-being of the animal. The measurements obtained with the device may be complemented with measurements of environmental parameters of the facility or culture medium, obtained both in real time and predictively.

Aquaculture is the only animal production sector with a wide growth margin worldwide. Currently, aquaculture contributes <NUM>% of the products derived from the sea, this contribution being expected to increase by about <NUM> million tons in the year <NUM>.

In the last decade, important advances have been made in the formulation of diets, diagnosis and disease prevention and genetic improvement programs. However, an urgent demand from the industry is the development and implementation of new biological monitoring systems for both the environment and the cultured animals. The ultimate goal is to remotely and non-invasively monitor the metabolic and/or health state of cultured animals. This practice is necessary for the development of new cultivation techniques that enable guaranteeing animal well-being while maximising production efficiency in a scenario of global change, with an increase in temperature, acidification of seawater and a decrease in the concentration of dissolved oxygen in the water.

The use of tags to identify or mark fish, as described in <CIT>, has been a known method for more than <NUM> years. In their initial version, these tags were passive elements which simply identified the animal. These tags are usually attached to the body or to a fin. In document <CIT>, tags that are fixed to the fish's operculum (or gill cover) are described, but they are passive tags without any electronic elements in them.

More recently electronic versions have appeared, in which the reading of the tag is carried out wirelessly by radio frequency, but they are also limited to identifying each animal with a unique code, as for example in those described in document <CIT>.

One of the methods used for monitoring fish activity status is based on video camera recording and image analysis (document <CIT>). This method is complex and difficult to use routinely in the open sea or with high cultivation densities.

On the other hand, for years, miniaturised acceleration sensors have been used to study the activity of people. In the post "<NPL>) describe an algorithm for detecting the different activities of a person based on the acceleration sensor located in their pocket. The procedure is based on the acceleration to detect the type of movement carried out (running, walking, sitting, etc.). This algorithm is not compatible with the movement patterns of other living beings.

Similarly, document <CIT> refers to a system and method for detecting movement patterns in any type of object, animal or person by means of a device with a movement sensor that is attached to the individual. The system and method require classifying the type of movement according to a previously classified pattern. Classifying movement is not a sufficient condition to determine physical activity and breathing frequency, jointly and simultaneously, in fish.

In the post "Accelerometer tags: detecting and identifying activities in fish and the effect of sampling frequency", Broell et al. (<NUM>) describe the use of implantable acceleration sensors in fish to monitor the activity thereof. More specifically, the publication refers to an algorithm for detecting the different activities of fish such as the moment of feeding or escape. They use the acceleration obtained from an acceleration sensor located on the first dorsal fin by means of a Velcro®, without considering the breathing frequency.

A similar approach is described in "<NPL>) for evaluating the metabolic activity of fish by means of acceleration sensors, without considering the breathing frequency, and estimating the oxygen consumption based on the dynamics of the accelerations of the fish.

Finally, document <CIT> describes a system, method and apparatus for monitoring and/or displaying characteristics of a target. A remote unit is provided which is worn in a remote target's body or embedded in moving or standing objects. Each remote unit includes a data acquisition circuit and one or more internal sensors integrally formed on a self-contained application specific integrated circuit, or integrated circuit chipset. The system provides enhanced viewing capabilities by combining video images with collected data regarding the target.

The present invention describes a device for controlling and monitoring a metabolic state, activity and well-being of fish according to claim <NUM>, which allows autonomously, remotely and individually monitoring physical activity and breathing frequency. The present invention also describes a method for controlling and monitoring a metabolic state, activity and well-being of fish according to claim <NUM>.

Thus, the present invention enables the technical problems of the state of the art of obtaining the breathing frequency of the fish, and the physical activity, jointly and simultaneously; and of monitoring the level of physical activity related to breathing frequency, swimming speed and oxygen consumption, to be solved.

The device comprises a substrate, for example flexible, preferably a tag, which in the simplest form thereof comprises: an acceleration sensor; a control unit (microcontroller) configured to partially or completely execute an activity-monitoring routine; a memory; a battery; an external measurement unit for downloading data, and optionally for processing thereof; optionally, a transmitter-receiver for optical, electrical, magnetic or electromagnetic communication between the substrate attached to the fish's operculum (or gill cover of the fish) and the external unit.

The acceleration sensor is an inertial device which provides acceleration data in three orthogonal axes, called x, y, z; and which enables the detection of small movements of the gill cover and the displacement of the fish, in the form of accelerations. The accelerations are stored in the memory and processed, completely or partially, by the microcontroller in order to quantify the breathing frequency and the level of physical activity.

The microcontroller provides the computing power for executing, completely or partially, the activity-monitoring routine that enables the calculation of physical activity and breathing frequency. For this, it has multiple modules that enable the control, storage, processing, and communication of the data generated by the acceleration sensor. The microcontroller provides a communication interface with the external unit that enables the programming, configuration and download of the data generated by the acceleration sensor. Likewise, it provides an internal interface to communicate with said acceleration sensor.

The memory is preferably non-volatile and is used to store the activity-monitoring routine, the acquired accelerations and the data resulting from the analysis of the physical activity and breathing frequency. The microcontroller has a power management unit to minimise battery consumption during periods of inactivity. The microcontroller has an event planning unit for the temporal execution of the experiments (data collection from the acceleration sensor and complete or partial processing). Events can be programmed in the memory or triggered from the external unit.

The battery is, in an exemplary embodiment, rechargeable and high-performance to provide enough energy to the rest of the components of the electronic circuit (acceleration sensor, microcontroller, memory, and the transmitter-receiver when present) during the useful life of the device.

The substrate is temporarily or permanently located in the gill cover of the fish to be monitored. Implantation in the gill cover can be done for example by means of perforations for the fixing thereof, or by means of a clamp mechanism, or by means of an adhesive substance. By means of the acceleration sensor, the movements of the fish while swimming, as well as the movements of the gill cover, jointly and simultaneously, are recorded in the form of accelerations. Both movements, which are fused into a single multidimensional signal, are separated by processing the data acquired by the acceleration sensor and are used to determine the swimming activity and the frequency at which the fish breathes. The data obtained by the acceleration sensor located in the gill cover is stored in memory and, subsequently, completely or partially processed by the control unit. In order to read the data from the device, for example, the fish is captured, the substrate is removed and the information stored in memory is downloaded onto a computer by means of the external drive; or, without removing the device, the data is downloaded by means of optical, electrical, magnetic, or electromagnetic communication.

The activity-monitoring routine is based on the calculation of the gill cover frequency in the direction that is normal to the plane of the gill cover, z axis. In addition, a statistical calculation of the accelerations that are coplanar to the gill cover, xy plane, is carried out to obtain an indicator of fish activity.

If the fish shows symptoms of stress, malnutrition or disease, among others, it will breathe at an abnormal frequency, and the behaviour thereof may be affected by erratic movements of high activity or a rest state. After a behaviour study, which is specific to each species, culture condition and development phase, it is possible to establish a comfort function, such that based on the acceleration sensor readings, the breathing frequency and physical activity having been extracted, the metabolic state and degree of well-being of the animal is determined. This determination may eventually be refined by means of readings of environmental parameters, obtained both in real time and predictively by means of other sensors.

As previously described, there are commercial tags for identifying fish, but in all cases they are passive and only transmit an identification code of the animal. There are also research groups which work with acceleration sensors in fish, but they only record patterns of swimming movement, without taking into account the breathing frequency in any case. Thanks to the device of the present invention, which records swimming and breathing movements, jointly and simultaneously, with a single sensor device, reliable measurements of the degree of well-being of the fish can be obtained.

In an exemplary embodiment, the components of the electronic circuit are mounted on the preferably flexible substrate by means of encapsulation techniques such as, for example, inverted circuit technology, wire soldering or surface mounting. Also in an exemplary embodiment, the water-resistamt (or impervious) coating is made of insulating epoxy to prevent water contact with the components of the electronic circuit.

In an exemplary embodiment, the control unit is configured to completely execute an activity-monitoring routine comprising filtering and analysing the multidimensional signal obtained by the acceleration sensor. The analysis determines the breathing frequency and physical activity of the fish. The external unit downloads the data obtained in the analysis.

In an exemplary embodiment, the control unit is configured to partially execute an activity-monitoring routine. In the external processing unit, after downloading the data, these are filtered and processed to determine the breathing frequency and physical activity.

In another exemplary embodiment, the control unit is configured to acquire the accelerations that are stored in memory. In the external processing unit, after downloading the data, these are filtered and processed to determine the breathing frequency and physical activity.

To complement the description that is being made and for the purpose of helping to better understand the features of the invention according to a preferred practical exemplary embodiment thereof, a set of drawings is attached as an integral part of said description in which the following is depicted in an illustrative and non-limiting manner:.

Below, an exemplary embodiment of the present invention is described with the aid of <FIG>.

The substrate of the device for monitoring fish of the present invention is configured to be placed on the fish's operculum (or gill cover of a fish) to determine different types of physical activity and breathing frequency. <FIG> shows the substrate of the device (<NUM>) already placed on the gill cover of a fish (<NUM>) and the three orthogonal axes (x, y, z) in which the accelerations are measured have been represented. For the monitoring, the acceleration measurements in the xy plane (<NUM>) are used, which is coplanar to the gill cover, from which the swimming movement of the fish is extracted; and, in addition, the measurements of acceleration in the z axis (<NUM>), which is normal to the gill cover, from which the breathing frequency of the fish is obtained based on the movements of the gill cover.

<FIG> shows the electronic circuit diagram of the device (<NUM>). This electronic circuit is installed on a flexible substrate and protected from water by an impervious coating.

In an exemplary embodiment of the invention, the control unit (<NUM>) includes a communication interface (<NUM>) with an external unit (<NUM>). This communication is carried out by means of an optical, electrical, magnetic and/or electromagnetic transmitter/receiver. In the external unit (<NUM>) the activity-monitoring routine is executed, completely or partially.

The interface (<NUM>) enables the programming of the control unit (<NUM>) by the external unit (<NUM>).

The control unit (<NUM>) may further be configured to execute, in a microprocessor (<NUM>), completely or partially, the activity-monitoring routine. The control unit (<NUM>) further executes an experiment-planning routine. This routine enables the timing and synchronisation of the data collection of the acceleration sensor (<NUM>) to be controlled during a determined period of time.

Likewise, the control unit includes an energy manager (<NUM>) to reduce energy consumption during periods of data collection. The subsystem for computing the acquired acceleration data (<NUM>) comprises a data analysis routine to determine the breathing frequency and the physical activity.

Preferably the battery (<NUM>) is of minimal size and weight but high performance to allow long periods of execution of the data-analysis routine.

In a preferred embodiment of the invention, the electronic circuit is arranged in an encapsulation that is as small as possible to minimise the weight and size of the device.

In a preferred embodiment, the electronic components are surface-mounted, and are chosen with the minimum size. The battery can be button-type, rechargeable with a minimum diameter. The support substrate for the entire system is preferably made of a flexible organic material to allow one of the ends thereof to bend on itself in order to connect the button-type battery on both sides.

<FIG> shows the different stages of the activity-monitoring routine that includes the procedure for calculating physical activity and breathing frequency in fish proposed in the present invention. The first necessary step is to obtain the acceleration data (<NUM>) in the three orthogonal axes x, y, z (ax, ay, az) either from the accelerometer (<NUM>), from the memory (<NUM>) or from the external unit (<NUM>).

The ac accelerations that are coplanar to the gill cover are contained in the xy plane, and the an acceleration that is normal to the gill cover corresponds to the z axis. These data are obtained with the acceleration sensor (<NUM>) or are stored in the memory (<NUM>) after being acquired, or are available in the external unit (<NUM>).

In an exemplary embodiment, the mean value (<NUM>) is subtracted from the acceleration data in the an direction that is normal to the gill cover, for example, the z-axis accelerations (az), and, subsequently, a count is made of the number and distance of maximums, and thus the breathing frequency (<NUM>) is determined. Likewise, the mean value is also subtracted from the ac coplanar acceleration data, for example, the x-axis (ax) and y-axis (ay) accelerations, respectively (<NUM>). From the results obtained, a physical activity rate (<NUM>) is determined.

Finally, a step of storing (<NUM>) in the memory (<NUM>) or in the external unit (<NUM>), the data obtained from the breathing frequency (<NUM>) and the activity rate (<NUM>) is carried out.

Claim 1:
A device for controlling and monitoring a metabolic state, activity and well-being of fish, intended to be attached to a fish's operculum, wherein the device comprises a substrate (<NUM>) with an electronic circuit and a waterresistant coating that covers the electronic circuit, the device being configured to join temporarily or permanently to the fish's operculum, of which the physical activity and breathing frequency is to be controlled and monitored during periods of ingestion and non-feeding throughout the day, wherein the electronic circuit comprises:
- a three orthogonal-axis (x, y, z) acceleration sensor (<NUM>) configured to acquire coplanar and normal accelerations of the fish's operculum jointly and simultaneously,
- a control unit (<NUM>) connected to the acceleration sensor (<NUM>) and which contains at least one microcontroller (<NUM>) configured to process the coplanar and normal accelerations obtained by the three orthogonal-axis (x, y, z) acceleration sensor (<NUM>), separating swimming movements and movements of gill cover to determine swimming activity from the accelerations in the z (az) axis which is normal to the fish's operculum and a frequency at which the fish breathes from the accelerations in x, y (ax, ay) axes which are coplanar to the fish's operculum, by executing at least one activity-monitoring routine,
- a memory (<NUM>) configured to store data acquired by the acceleration sensor (<NUM>) and/or data generated by the microcontroller (<NUM>) when executing an activity-monitoring routine, and
- a battery (<NUM>) connected to the control unit (<NUM>),
wherein the substrate (<NUM>) is configured to establish communication with an external device (<NUM>) to which the data acquired by the acceleration sensor (<NUM>) and/or the data generated by the microcontroller (<NUM>) are sent.