Gasterosteidae, Bonaparte, 1831

Gasterosteidae View in CoL

Two species of stickelbacks are native in Norwegian freshwater. Both species can also be found in both brackish and marine waters. In particular the three-spined stickleback Gasterosteus aculeatus Linnaeus, 1758 in common throughout coastal waters as well as marine waters along the Norwegian coast (Huitfeldt-Kaas 1918, Klepaker 1996). The nine-spined stickleback Pungitius pungitius (Linnaeus, 1758) has a more limited distribution. Sticklebacks are intensively studies globally, in particular the three-spined stickleback is used as a model species in a wide range of research fields (Östlund-Nilsson et al. 2007, Wootton 2009). The nine-spined stickleback has gotten less interest. This is also clear in Norway, where only five articles were retrieved by the search. Only one of the studies focussed on the nine-spined stickleback in some detail (Klepaker et al. 2013). Two studies focussed on parasites, but mainly in the three-spined stickleback (Rødland 1983, Soleng and Bakke 1998). Overall, we know almost nothing about the biology of the nine-spined stickleback in Norwegian ecosystems. This is in stark contrast to the three-spined stickleback, where we retrieved 49 articles by the search.

Many of the studies on three-spined stickleback focussed on the phenotypic variation observed in lateral bony plates – a trait that is extensively studied in this species. These studies concerned the large-scale (Klepaker 1995, 1996, Voje et al. 2013) and small-scale distribution (Le Rouzic et al. 2011, Østbye et al. 2016, Østbye et al. 2018) of the plate morphs among and within ecosystems, and how it differs depending on various selective processes (Myhre and Klepaker 2009, Bjaerke et al. 2010, Mazzarella et al. 2015). These studies also included the use of modern genetic/genomic methods (Taugbøl et al. 2014, Mazzarella et al. 2016). Also, the other main anti-predator defence system – the dorsal and pelvic spines – have been studied (Klepaker et al. 2012, Klepaker et al. 2013). These studies in general are set in an evolutionary context.

The three-spined stickleback is an important prey fish for many freshwater fishes, and several studies have investigated such predator-prey relationships (Jakobsen et al. 1988, L’Abée-Lund et al. 1992, Amundsen 1994). In an ecosystem context, distribution, transmission and importance of various parasites has also been studied in some detail ( Amundsen et al. 2013, Braicovich et al. 2016, Kuhn et al. 2016). This has also been studied in the context of sexual selection and spawning behaviour ( Folstad et al. 1994). In addition to this parasite focus, several studies have used three-spined stickleback to study toxic effects of various compounds (Wibe et al. 2002, Knag and Taugbøl 2013).

Even if the tree-spined stickleback has been studied in some detail, little is known about its population dynamics and ecosystem effects. This is unfortunate, in particular based on reports from the brackish Baltic Sea where changes in the stickleback density have had strong effects on numerous other species ( Bergström et al. 2015, Byström et al. 2015, Eklöf et al. 2020). This lack of basic biological information is shared by many other small-sized fish species – both in freshwater and in the sea.