A Test of Computer-assisted Matching Using the North Pacific Humpback Whale, Megaptera novaeangliae, Tail Flukes Photograph Collection

Testing was conducted of a computer-assisted system for matching humpback whale tail flukes photographs. Trials with a 12,000-photographs database found no differences in match success between matching by computer and matching by comparing smaller catalogs ranging in size from 200 to 400 photographs. Tests with a 24,000-photographs database showed that, on average, the first match was found after examining about 130 photographs whether the photograph quality was excellent, good, or poor. Match success did not appear to be strongly related to whether the tail flukes had especially distinctive markings or pigment patterns (recognition quality). An advantage of computer-assisted matching is the ability to compare new photographs to the entire North Pacific collection, where no bias is introduced based on expectation of resightings within or between specific areas, or based on expectation of behavioral role (e.g. matching “known” females to “known” females).

Bearbeitung von Fangproben mit neuen elektronischen Messmethoden

For 10 years the Institute for Fishing Technology, Hamburg (IFH) has been carrying out experiments in the brown shrimp fishery with beam trawls aiming at a reduction of unwanted bycatches. When the tests were transferred to commercial fishery conditions the personnel effort and costs increased markedly. It became e.g. necessary to install a deep-freeze chain to make it possible to evaluate more samples in the laboratory. This again required to increase the number of technicians for measuring the fish and shrimp samples, but also made it necessary to perform this work in the most rational and time-saving way by applying modern electronic aids. Though all samples still have to be sorted by species and have to be weighed and measured the introduction of electronic aids, however, like electronic measuring board and computer-aided image processing system, all weight and length data are immediately and digitally recorded after processing. They are transferred via a network to a server PC which stores them into a purpose-designed database. This article describes the applicationof two electronic systems: the measuring board (FM 100, Fa. SCANTROL), iniated by a project in the Norwegian Institute for Fishing Technology, and a computer-aided image processing system, focussing on measuring shrimps in their naturally flexed shape, also developed in the Institute for Fishing Technology in close collaboration with the University of Duisburg. These electronic recording systems allow the consistent and reproducible record of data independent of the changing day-to-day personal form of the staff operating them. With the help of these systems the number of measurements the laboratory could be maximized to 250 000 per year. This made it possible to evaluate, in 1999, 525 catch samples from 75 commercial hauls taken during 15 days at sea. The time gain in measuring the samples is about one third of the time previously needed (i.e. one hour per sample). An additional advantage is the immediate availability of the digitally stored data which enables rapid analyses of all finished subexperiments. Both systems are applied today in several institutes of the Federal Research Centre. The image processing system is now the standard measuring method in an international research project.