Population dynamics of two sympatric intertidal fish species (the shanny, Lipophrys pholis and long-spined scorpion fish, Taurulus bubalis) of Great Britain

Abstract

The shanny/common blenny (Lipophrys pholis) and long-spined scorpionfish/bullhead (Taurulus bubalis) are commonly encountered, sympatric species within much of Great Britain's rocky intertidal zones. Despite being prey items of the cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) respectively, and both contributors to the diet of the near-threatened European otter (Lutra lutra), little is known on the population dynamics of the temperate specimens of Great Britain. It is further less known of the degrees of sympatricity between the two fish species and to what extent they are able to coexist. The current study examines spatio-temporal distributions and abundances at various resolutions: monthly population dynamics of both species along England's Yorkshire coast and seasonal population dynamics along the Yorkshire coast and around the Isle of Anglesey, Wales. Studies of their abundances, sizes, degrees of rock pool co-occurrence and diel activities are further examined, which indicate coexistence is maintained when interspecific co-occurrence takes place only between specimens of similar sizes, thus demoting size-related dominance hierarchies.

Lipophrys pholis is larger, grows faster and is in better condition in protected than in unprotected rocky shores

“…The positive impact of the reserve effect upon a population, however, may not be reflected in all specimens because inhabiting a protected site can lead to higher rates of inter‐ and intraspecific co‐occurrence, thus resulting in the spillover of competitively excluded specimens (Barrett et al, 2018). A higher abundance of larger predators migrating from the subtidal system to the protected area could increase mortality rates on intertidal fishes (Macpherson, 1994; Willis & Anderson, 2003), especially on smaller individuals.…”

“…Different techniques can capture fish of different developmental stages, even within the same location (Barrett et al, 2020;Beja, 1995). Thus, to reduce sampling technique bias and detect differences due to local factors, studies that evaluate fish body conditions and growth parameters at different sites should ensure sampling protocols are consistent (Compaire & Soriguer, 2020).…”

“…This procedure was proven to be efficient in catching juveniles and adults of L. pholis in LU and NES (Barrett et al, 2020;Velasco et al, 2010). In laboratories at the University of Hull (England) and at the University of Cadiz (Spain), specimen total length (TL) was measured to the nearest millimetre and total weight (WT) to 0.01 g.…”