Guest Blog: ciBioBase and Arctic charr habitat in Windermere, U.K.

By Dr. Ian J. Winfield and Joey van Rijn

The Arctic charr (Salvelinus alpinus) is well appreciated as an important fisheries species in many northern areas of the world.  In addition, it is equally important to evolutionary biologists because of this species’ frequent development of ‘morphs’ or ‘types’ and their bearing on our understanding of mechanisms of speciation (Figure 1).  In the U.K., this fascinating fish is also recognised as having great nature conservation value.

Figure 1.  A female (top) and male (bottom) Arctic charr from Windermere, U.K.  Photo courtesy of the Center for Ecology and Hydrology)

Windermere is England’s largest lake and has been at the forefront of several areas of Arctic charr research for many decades, with the notable exception of studies of their spawning grounds (Figure 2).  Despite their long appreciated significance for the coexistence of autumn- and spring-spawning Arctic charr types, local spawning grounds have not been studied in any detail since their original brief description in the 1960s.  At that time, laborious and spatially-limited direct observations by divers showed that spawning requires the availability of gravel or other hard bottom habitat.  New information on these critical areas is needed by ecologists and evolutionary biologists and, more urgently, by fisheries and conservation organisations responsible for the management of Windermere.

Figure 2.  Breathtaking view of Windermere’s north basin; home to several spawning populations of Arctic charr.  Photo courtesy of Dr. Ian Winfield.

We are currently using the newly developed bottom hardness capability of ciBioBase to survey and characterise the spawning grounds of Arctic charr in Windermere.  Limited underwater video is being used for ground-truthing, but the combination of a Lowrance HDS-5 sounder with ciBioBase is allowing us to investigate the known spawning grounds with unprecedented speed (Figure 3).  For the first time, we have been able to document in detail the bathymetry and bottom features of a long-monitored (for spawning fish) spawning ground just north of the island of North Thompson Holme in the lake’s north basin.  ciBioBase is also enabling us to examine other known spawning grounds in Windermere and to expand our coverage to other potential areas previously unstudied.

Figure 3. An example ciBioBase output of bottom composition on and around the Arctic charr spawning ground of North Thompson Holme in the north basin of Windermere

The rapidity of the field component of hydroacoustic surveys is well known.  ciBioBase now offers us a similarly fast method of hydroacoustic data analysis for key environmental characteristics in relation to the spawning of Arctic charr.  This new approach helps us to dramatically increase our return on investment and also allows us to review results within hours of coming off the water, leading in some cases to us adapting our field plans on the basis of initial results.

Dr. Ian J Winfield is a Freshwater Ecologist at the Centre for Ecology & Hydrology in Lancaster, U.K.  He has over 30 years of research experience in fish and fisheries ecology, hydroacoustics, and lake ecosystem assessment and management.  Dr. Winfield sits on several regional, national and international advisory boards and is the current President of the Fisheries Society of the British Isles (FSBI).

Joey van Rijn is an undergraduate student currently following a BSc. degree course in Applied Biology at the University of Applied sciences, HAS Den Bosch, in the Netherlands. He is experienced in ecological and particularly phenological research including work on temperature-induced differences between urban and rural areas in the timing of blossoming and leaf unfolding in shrubs.  He has also been involved with the development of fish ways for standing waters in the Netherlands. Joey is currently undertaking a research internship at the Centre for Ecology & Hydrology in Lancaster, U.K., where his research mainly focuses on using hydroacoustics to investigate Arctic charr spawning grounds in Windermere.

Legacy applications of commercial sonar

At Contour Innovations we stand on the shoulders of giants who proved commercial depthfinders are precise scientific instruments for the measurement of aquatic plant abundance and distribution in lakes.   As early as 1980, researchers saw the potential for fathometers/chart recorders/depth finders/sonar/echosounders – whatever you want to call them – to substantially reduce time, effort, and cost in assessing aquatic plant communities in lakes (Maceina and Shireman 1980).

The commercial sounders of the 1980’s had only a fraction of the power and resolution of what Lowrance manufactures today (not to mention integration with GPS) and investigators still boasted of the quality and cost-effectiveness of the data acquired.  Here are some excerpts:

Maceina and Shireman (1980): “The principle advantage of utilizing a recording fathometer for vegetation surveys is that savings in time and manpower can be accomplished.  In Lake Baldwin, 14 transects covering a total distance of 11.3 km were completed in three hours.” p 38.

Duarte (1987): “Direct harvesting is an expensive and time-consuming procedure (see Downing and Anderson 1985).  Two SCUBA divers require 20 min on average to harvest the biomass of six replicate quadrats at a single depth.  In contrast, six replicate echosounder transects require only 8-35 min to obtain biomass estimates for all depths, with the actual time required dependent on the littoral slope and the depth to which the plants grow.  Additional advantages of the echosounder method are (1) a continuous record of the vegetation, rather than at discrete depths only, with the latter resulting in inaccuracies when the mean biomass values are estimated, (2) nondestructive sampling, which allows monitoring of the growth of stands over time and (3) simultaneous recording of other variables such as percent cover (Stant and Hanley 1985), volume occupied by the submerged vegetation, and littoral slope (Duarte and Kalff 1986), which influences macrophyte biomass.” p. 734

In fact, Duarte (1987) publishes biomass prediction equation from acoustic estimates of plant height (a ciBioBase output) for 22 aquatic plant species.

Thomas et al. (1990): “Fortunately, shallow range (0-7 m) chart recorders are standard on many low cost (less than $400) commercial echosounders, so the data acquisition equipment costs are relatively low with respect to fisheries acoustic assessments, which makes this procedure relatively nontechnical and very cost effective” p. 810

The concept of using commercial acoustics for mapping lake bottoms is established and proven.  Contour Innovations has refined, streamlined, and automated the methodology with ciBioBase and delivers an intuitive visualization of the complex underwater world we call littoral zones.

A Raytheon DE-719 “fathometer” relic when plant biovolume was measured on paper charts with the use of planimeters.  Photo from www.euronet.nl.
Paper chart from a Raytheon DE-719 displaying dense hydrilla canopies and bottom in a central Florida lake.  Reproduced from Maceina and Shireman 1980; J. Aquat. Plant Manage.

Classic Literature
Duarte, C.M. 1987. Use of echosounder tracings to estimate the aboveground biomass of submerged plants in lakes. Canadian Journal of Fisheries and Aquatic Sciences 44: 732-735

Maceina, M and Shireman, J. 1980. The use of a recording fathometer for determination of distribution and biomass of Hydrilla. Journal of Aquatic Plant Management 18:34-39.

Maceina, M.J., Shireman, J.V., K.A. Langland, and D.E. Canfield Jr. 1984. Prediction of submerged plant biomass by use of a recording fathometer.  Journal of Aquatic PlantManagement 22: 35-38.

Stent, C.J. and Hanley, S. 1985. A recording echosounder for assessing submerged aquatic plant populations in shallow lakes. Aquatic Botany 21: 377-394

Thomas, G.L., Thiesfeld, S.L., Bonar, S.A., Crittenden, R.N., and Pauley, G.B. 1990. Estimation of submergent plant bed biovolume using acoustic range information. Canadian Journal of Fisheries and Aquatic Sciences 47: 805-812.