Abstract
In fisheries biology of the late 19th century, the challenges posed to taxonomy by Darwinian theory intersected with attempts to increase the productivity of marine populations. Addressing both discourses, the influential German zoologist Friedrich Heincke developed a set of methods to determine exactly the differences between varieties or races of herring. In taxonomy, his methods contributed to the development of a biological species concept; in fisheries biology, they allowed tracing the herrings' migrations, which ultimately aided in divising schemes for sustainable fisheries. Heincke's use of mathematical statistics, some of them borrowed from anthropometry, served to distinguish his ‚exact’ approach from that of typological taxonomists. Beyond its use as a rhetorical ploy, exactness gained meaning in the epistemic regime of exact reproduction of measurements, which entailed the replication of measurement techniques for the purpose of comparison e.g. of herrings caught at different locations. This exactness was enabled by the formalisation of the process of taxonomic identification