Aquaculture Newsletter

Dissolved Oxygen, Conductivity, Temperature and Currents



Introducing the HOBO U26-001 Dissolved Oxygen and temperature data logger. Using optical sensing technology from In-Situ Inc the U26 is a very reliable and stable platform to measure and log dissolved oxygen levels and changes in the environment. The only consumable part is the U26-RDOB-1 sensor cap, which lasts six months before needing replacement. With excellent supply lines from the manufacturer we can support and advise on the management of these consumables throughout the life of the product. In seawater you can use the anti-fouling guard to stop buildup of organics and precipitates on the surface of the sensor. This logger must be used with either the BASE U-4 or U-DTW-1 waterproof shuttle and HOBOware Pro software to calibrate, launch and readout the logger in the field.



The HOBO U20-001-04 Stainless Steel or Titanium 0-4m range water level logger can be used as a logging barometer in order to convert mass based mg/L data to %DO using barometric pressure data



In order to process dissolved oxygen data as well as monitoring the general health of the marine environment it is important to take measurements of the changing salinity levels in the water the fish or shellfish stock are living in. The HOBO U24-002C salinity/conductivity logger is an ideal tool for this, especially where there are changes in salinity associated with estuaries or river mouths in addition to high rainfall. In the open ocean it may only be necessary to take a conductivity or salinity measurement at the start and end of a dissolved Oxygen measurement due to the general stability ocean water salinity however fish farms at coastal locations may be subject to changes in salinity levels, all of which may affect to breeding and feeding cycles of the fish as well as affecting recorded levels of dissolved Oxygen. The U24-002C can be used in conjunction with the U26-001 dissolved Oxygen logger using the same base or shuttle interfaces and software



Measuring water temperature is vital in the proper management of the fish resource in a fish farm so having low cost temperature only dataloggers would be an excellent field  tool. The HOBO U-TBI-001 Tidbit V2,   U22-001 & UA series temp (and light level UA-002) dataloggers are small and highly accurate ±0.2°C devices (UA is ±0.5°C)  that can be set at depths of up to 300m (150m for U22 & 30m for UA). With a five year battery life (Tidbit and U22, 1 year for UA) these can be used indefinitely and these also can be interfaced to a Windows PC or Mac using the same  coupling devices as for all the other loggers used here running HOBOware or  HOBOware Pro  software





The measurement of current flows in seawater can provide an insight on how nutrients and oxygen passes through the environment and also where  potential contaminants come from. Finding low cost marine current  meters can be challenging at the best of times however Lowell Instruments LLC has produced a range of low cost tilting current meters such as the TCM-1 and TCM-3, which utilize Accelerometers and Magnetometers to determine both current velocity and compass bearing, for a fraction of the cost of equivalent marine grade EM current  meters. These can pair up with the  proprietary MAT-1 data logger which allows unattended recording of data and storage to a micro SD Card and depending on logging rate, battery life of up to 36 months