Executive Summary – MF0145 Development of data storage tags (DST) (phase 3): tag miniaturisation & development of fishery independent methods of data retrieval.
Introduction
Two “generations” of electronic data storage tag (DST) were developed by CEFAS over the 10 years prior to the start of this project. These have been used successfully to study the geographical movements and behaviour of free-ranging marine fish. CEFAS were the first ever to undertake a large-scale deployment of DSTs on a marine fin-fish species and subsequently the technology has become established world-wide as a valuable method for gaining high quality information on behaviour and distribution of fish in their natural habitat. This R& D project develops from this background and has two separate but linked aims. The first was to miniaturise the Mk 3 electronic data storage tag so that it would be small enough for deployment on male and juvenile plaice, juvenile cod and on Dover sole. The second was to develop fishery independent methods of data retrieval to maximise data recovery and improve the cost benefit of electronic tagging.
The overall key purpose of the work was to develop appropriate specialised technologies to support CEFAS’ biological research programmes on marine fish that provide the understanding of fish behaviour and ecology that underpins fisheries science.
Summary of results
1. DST miniaturisation (Mk 4 DST).
We have succeeded in developing state-of-the-art devices that are the smallest geolocating data storage tags currently available. The design of the tag and the layout and construction of the circuit boards proceeded as planned. Construction of the first prototype tags was delayed due to problems with the memory die. CEFAS engineers work with the memory die manufactures and the die design problems were resolved. Subsequently, testing and production of the tag proceeded largely as planned. Additional financial support derived from CEFAS’ commercial partnership with Lotek Wireless has resulted in increased functionality (e.g. the inclusion of a day-log, on-board light-based geolocation estimation, temperature correction of the on-board clock to within 1ppm (~32secs / year) and the implementation of a family of devices based on a common design. This has added considerable value to the project at no additional cost to Defra. The final tag is within the original size specification but with enhanced functionality. The technical specifications for the tags and circuit diagrams are attached at Appendix II.
2. Fishery independent data retrieval.
We have succeeded in developing a prototype pop-up, GSM telephone tag suitable for deployment on large fish like basking sharks. The data logging circuit is based on the successful CEFAS Mk 3 DST. Data transmission is achieved using a Siemens TC35 cellular GSM telephone engine and relies in the tag drifting close to shore in order to access the terrestrial cellular telephone network. The pop-up function is achieved using an “electric match” that acts as the primary release mechanism. Two tag housings have been designed and built, one of titanium for operations to depths of 1000 m, and a lighter one of PVC for operations to depths of 400 m. Problems were encountered with the circuit design during the tag construction which was eventually traced to signal integrity problems resulting from interference on the connections around the components that interface the micro-controller to the flash memory. Although the fault was rectified, the delays in construction resulted in it not being possible to deploy any tags on basking sharks in 2003 as planned. However, 9 tags have be constructed and are now (April, 2004) ready to be deployed on basking sharks in May and June 2004
Additional Objectives
Due to delays in formulating an agreed follow-on R&D programme, this project was extended during 2003/04 and the following four objectives were added to the programme.
3. Review of development of prototype “pop-up” GSM telephone tag.
Because we have not yet been able to deploy “pop-up” GSM telephone tags on basking sharks, we have not been able critically to review progress and outcome of the development and field test of these tags. This work will take place as part of a new Defra funded project (MF0155) which has the further development of fisheries independent data retrieval as one of its objectives.
4. Appraisal of methods that could be used to monitor behavioural events.
We have examined the available technology that could be used to monitor behavioural events such as feeding. We have identified that monitoring jaw movements is likely to be the simplest and most robust approach for measuring feeding activity. We have also identified that the use of a magnetoresistive sensor located on one jaw and a small magnet located on the opposite jaw is likely to be the best technical solution for monitoring jaw movements.
5. Review of lab-based telemetry systems.
We have reviewed various methods for data acquisition from putative feeding sensors deployed on aquarium-held cod and have identified infrared optical telemetry to be the best technical solution for telemetering information about jaw movements.
6. Build and test a low power [feeding] sensor interface circuit.
We have built and tested a low-power sensor interface circuit and established that the identified sensor will run at a current down to approximately 10 μA in the quiescent state (equivalent to 87 mAh y-1) and at 394 μA when continuously sampling at 32 samples s-1 (equivalent to 3.44 Ah y-1). This sensor circuit should therefore be suitable for integration into an acoustic telemetry tag with a life of up to 12 months. When used as part of a data storage tag application, it may become necessary for the sensor be powered over shorter periods, and during periods of particular interest, in order to achieve multi-year recording.
Future developments.
While further reduction in overall tag size is not currently seen to be a high priority, further refinement and miniaturisation of the basic electronic circuits will be desirable in order maintain the small size, while allowing for the addition of more memory, more advanced on-board processing capabilities, additional sensors (e.g. behaviour sensors) and fisheries independent data retrieval capabilities. However, fisheries independent data retrieval, sensor development and onboard data processing are all identified as priority areas for further development.