The objective of this poster is to show how the idea of adding animal movement data from current acoustic fish tags and future “Integrated Tags” to existing and future Ocean Observation Systems provides information of high economic value and complements biologging data which is only obtainable from larger fish because of the size of the tags.
An Emerging World Wide Fish Tracking Network
Acoustic tagging has been a well established tool for determining movements and behaviour of free-swimming fish for decades. In recent years, there has been a significant expansion of acoustic Passive Tracking (see Heupel, Semmens and Hobday, 2006, for a review) in which stationary receivers log the passage or residency of tagged fish over extended periods of time. LaCroix and Voegeli (2000) first demonstrated the feasibility of employing passive tracking employing a long line (42 km in this case) on the ocean floor to monitor fish passage. This concept formed the basis of the Pacific Ocean Shelf Tracking Project (POST) whose infrastructure includes a number of acoustic curtains extending from California to Alaska with the initial intent of determining what was happening to salmon smolt when they leave the rivers and enter the ocean. In addition, the arrays have provided valuable data on the migration of a number of other species.
The success of the early initiatives described above has led to an expanding number of projects such as the Australian Acoustic Tracking and Monitoring Systems (AATAMS), Florida Atlantic Coast Telemetry Project (FACT) and the Ocean Tracking Network (OTN). The network has two important features
All receivers are capable of detecting all transmitters
ID codes transmitted from each tag are unique (i.e. each individual animal can be identified)
which combine to provide the means and motivation for various initiatives to come together as an informal worldwide tracking network. This is allowing researchers to gather data on tagged fish far beyond what would be possible with a project specific installation. Figure 1 shows the extent of the network in coastal waters around the world. Not shown in the Figure, but also a valuable source of information, are extensive arrays of receivers in various river systems and estuaries enabling data exchange between marine and fresh water environments.
Figure 1. The Emerging Worldwide Fish Tracking Network
Table 1 summarizes the key characteristics of the existing network:
Transmitter Size and Life
Various, ranging from a few grams suitable for very small fish (down to 10 grams or less) to larger more powerful versions. Transmitting life in excess of a year, and often extending over a number of years, is common.
Number of Tagged Fish
Currently, the number of fish with active transmitters is over 20,000 and this number is growing.
Transmitted periodically (typically on the order of once per minute).
All transmitters send a unique ID code. Some versions also transmit sensor data (depth, temperature and/or acceleration being the most common).
Data is logged from any transmitter within range (a few hundred metres to more than a kilometre depending on the particular transmitter ).
In the simplest versions, data is accessed by recovering the receiver. Other versions support remote communication via satellite or underwater modem.
The current and planned infrastructure has two major shortcomings:
For many species, knowledge of the nature of open ocean migration is important but, as can be seen form Figure 1, there is virtually no coverage outside coastal waters.
Because of the difficulty, and often impossibility, of researchers obtaining approvals for surface buoys, the vast majority of receivers are underwater meaning that access to data, either by recovery of the receiver itself or acoustic upload, is infrequent, time consuming and expensive.
Integration of a tracking receiver into ocean observing systems now in place addresses both issues above. Candidate observing systems include various fixed surface buoys, Argo profiling floats and buoys used in the Global Drifting Program. As each of these programs involves thousands of buoys and central data collection, such integration would cause the biological data obtained from existing tagging programs to be greatly increased. Clearly, the coverage of such receiving sites of opportunity will be much sparser than current coastal receiving arrays which have been installed at critical points where fish are known to pass. On the other hand, almost all detections would have major value as has been demonstrated time and time again in the past when extension of receiving arrays has shown fish migrations far in excess of what had been previously assumed (see O’Dor, 2009, for example).
While integration details would be different for each type of observing system, they shouldn’t be onerous. A basic receiver which can be polled for detection data consists of a hydrophone which is approximately a 16 mm by 16 mm cylinder and a 5 cm by 15 cm printed circuit board which consumes about 3milliwatts. Higher performance receivers (i.e. more range capability) are possible if the power budget can be increased.
Future Integrated Tags will Fill in the Data Gaps
Biologging tags of various types have been invaluable for “the collection of habitat utilization, movement patterns and behaviour of large marine predators” as they move through the ocean (see Costa, 2009, for example). However, for the large majority of species too small to carry these tags, one of two compromise approaches is used:
Archival Tags which store sensor values in memory with data recovered when and if the fish is recaptured
Acoustic Telemetry Tags as described above which transmits sensor data in real time
Each approach, of course, has its limitations. With Archival Tags, no data is recovered unless the fish is recaptured while, with Telemetry Tags, no data is available for the time that the tag is not near a receiver (potentially significant in the case of migrating fish). The Integrated Tag concept now under development combines the features of both approaches and adds a small acoustic modem which uploads stored sensor data when in the presence of a compatible receiver (i.e. the same role as is performed by a satellite transmitter in many biologging tags).
Two capabilities significantly enhance the value of this type of tag:
Business Card Sensor is essentially a miniature acoustic receiver within the tag which logs the ID code of any other fish which comes within range.
While these sensors are not feasible for the smallest acoustic tag, tags will be significantly smaller than biologging tags permitting them to be used on fish weighing on the order of one kilogram or more. Versions of Integrated Tags without one or both of these capabilities also have the potential to deliver more useful data than is currently possible and would be usable on smaller fish.
The integration of acoustic telemetry receivers into existing and future ocean observing systems and the development of Integrated Tags of various types will provide a great deal more data from existing tagging programs as well as create additional new types of data which to date have only been obtainable from fish large enough to carry biologging tags or which are likely to be recaptured making the use of archival tags realistic. Figure 2 shows how this information comes together and how increasing any “dimension” – number of simple or integrated tags, number of dedicated receivers, receivers integrated with ocean observatories or mobile receivers – creates the potential for higher quality data on where fish went, what they experienced and their interaction with other fish.
tracking receivers into Ocean Observatory Systems and Integrated Tag development
Costa, D.P. (2009) TOPP as a Marine Life Observatory: Using Electronic tags to monitor the movements, behaviour and habitats of marine vertebrates. Community White Paper OceanObs’09. Ocean Observing 2009
Heupel, M. R., J. M. Semmens and A. J. Hobday (2006). Automated acoustic tracking of aquatic animals: scales, design and deployment of listening station arrays. Marine and Freshwater Research 57(1): 1-13.
Lacroix, G.L., and Voegeli, F. A. 2000. Development of automated monitoring systems for ultrasonic transmitters. In Advances in fish telemetry. Edited by A. Moore and I. Russell. CEFAS, Lowestoft. pp. 37-50.
O’dor, Ron (2009) The Ocean Tracking Network. Community White Paper OceanObs’09. Ocean Observing 2009