FISHERY, AGRICULTURE AND WILDLIFE APPLICATIONS
Data collection for statistic purposes with numbers of, circumference, diameters, lengths, heights and positions, can basically be done the same way, independant of if working with trees in the forest or fish in the sea. Our instruments and applications designed for forest measuring work often overlap other areas of operation, for example fishery research
Wildlife management in South Africa.
Image courtesy of X Combrink Zululand Nile Crocodile Research Programme Ezemvelo KZN Wildlife & University of KwaZulu Natal South Africa
Haglöf Sweden’s wide range of mechanical caliper models is suitable for or can be adapted to fit fishery and wildlife management. With our in-house production facilities and long experience we have great capacity to customize the products and software applications. It also helps to be curious – and we are!
Together with specialized user groups and suppliers, Haglöf Sweden have developed solutions including electronic calipers and remote sensors to measure and store fish lengths and diameters at sea. Information is collected and stored digitally, and can later be transferred to handheld or PC for further processing and storing. The custom designed application is adapted to control fish stock, size and quality – both for research and for commercial reasons, and the results are aimed to achieve a better understanding of migration and movement, growth and survival rates.
The overall measurement of a fish, whether it is fork-tailed or round tailed, is taken from the snout on the upper jaw to the end of the tail. For freshwater fish, the measurements used are total length and girth. The total length is the maximum length of the fish, with the mouth closed and the tail fin pinched together. Conversely, most marine refer to the “fork length”, and scientists often use “standard length” which is to the end of the fleshy part of the body. “Standard length” has the advantage of not being affected by minor damage to the tail fin, nor does it give too much credit to a fish for the relatively light weight tail when calculating a fish’s condition.
Eastern Desert, Egypt, January 2015. Coring Acacia tortillis.
“Measurement Procedures: Linear Measurements can either be taken with calipers (straight-line measurements) or with a flexible tape measure (curved measurements). The decision is one of accuracy, precision, cost, and convenience. Curved measures tend to be less accurate and less precise (Bjorndal and Bolten, 1989; Frazier, 1998; Pritchard et al., 1983; Shoop and Ruckdeschel, 1986) because of irregularities and epibionts on the surface of the turtle’s shell. Also, in the juveniles of some species, the vertebrals are keeled, and the posterior carapace in some species has a steep change in slope which make curved carapace length difficult to measure with accuracy and precision.”
“Sea turtles are measured to relate body size to reproductive output, to determine minimum size at reproduction, and to monitor nesting female size at a rookery. Changes in nesting female size can, for example, be indicative of either a declining population or in some cases, an expanding population. At foraging grounds, they are measured to determine size classes of turtles, which in turn can provide important information about the demography of a population. Mark recapture studies in which turtles are captured, marked and released, then later recaptured, can provide estimates of population size. Repeated measurements of tagged turtles during mark recapture studies can provide estimates of growth rates. As with all other data, measurements need to be as precise, i.e. free of error, as possible. Error can creep into the measurements in many ways. Different personnel may take measurements differently. They may measure the turtle from different points. Different tape measures can vary substantially from each other. The same tape measure can deteriorate over time (and stretch) and thus result in erroneous measurements. Hence, tapes and calipers should be calibrated regularly.
Other special projects for applications at sea include custom models and special, adapted software for our electronic calipers to measure divergence in chain links for off-shore riggs. The off-shore calipers are used in extreme conditions and constructed to sustain all types of weather and harsh use with special reinforced material.
In wildlife management, the Gator Eyes Laser Pointers can be used to measure crown width on elks and size of eagles’ nests from a distance.
The image to the left shows measuring and classifying of sheep at Elsbo Gard in Sweden.