Perch and pike recruitment in coastal bays limited by stickleback predation and environmental forcing

• Published in: Estuarine, coastal and shelf science coastal and shelf science, 2020-11, Vol.246, p.107052, Article 107052
• Main Authors: Donadi, Serena, Bergström, Lena, Bertil Berglund, Johnny Mats, Anette, Bäck, Mikkola, Roosa, Saarinen, Anniina, Bergström, Ulf
• Format: Article
• Language: English
• Subjects: Baltic Sea; Ecology; Ekologi; Fish and Aquacultural Science; Fisk- och akvakulturforskning; Path analysis; Perch; Pike; Predator-prey reversal; Stickleback
• ISSN: 0272-7714; 1096-0015; 1096-0015
• DOI: 10.1016/j.ecss.2020.107052

Role reversal can shift fish communities from predator to prey dominance. In the Baltic Sea, the increase in abundance of the small-bodied three-spined stickleback (Gasterosteus aculeatus) has co-occurred with declines of coastal predatory fish, such as perch (Perca fluviatilis) and pike (Esox lucius) in many areas. Recent studies have pointed at predator-prey reversal as a possible mechanism explaining these trends, but conclusive evidence on the phenomenon or its relative importance compared to other drivers is at present open to question. In this study, we applied path analysis to quantify the potential role of stickleback in limiting the recruitment of perch and pike in enclosed bays (i.e. flads) along the Swedish and Finnish coasts. We constructed a causal network model based on vast field data combined with data from GIS and orthophotos, representing fish abundance, hydrographic factors, habitat-forming vegetation, anthropogenic disturbances and geomorphological factors. We found that stickleback abundance had as large effect on larval densities of perch and pike as environmental forcing, represented in our best models by the thermal regime of the flads. Larval densities decreased with stickleback abundance and increased with increasing summer cumulative temperature at a similar rate. Stickleback abundance, in turn, was strongly limited by flad openness, expressed as the number of flad openings to the sea, and increased with vascular plant cover (flad averages). Our study shows that predator-prey reversal could be a strong determinant of perch and pike larval survival, and suggests that the prevalence of more enclosed flads, which are less accessible to stickleback, may be crucial for recruitment of these piscivores. This implies that (1) in areas with, or prone to, increased stickleback abundance, habitat restoration and actions to conserve piscivore populations should primarily focus on more enclosed flads, and that (2) dredging and canalization to enhance boating in these areas could have detrimental effects on piscivore recruitment by decreasing water temperature and enhancing stickleback abundance, hence restricting larval growth and survival. [Display omitted] •Stickleback predation limits recruitment of perch and pike.•Flad openness affects perch and pike larval densities by determining the abundance of stickleback.•Enclosed flads should be the target of habitat conservation and restoration.