The ways in which fish use estuaries: a refinement and expansion of the guild approach

TLDR

Fish use estuaries in diverse ways, a topic first systematically described in 2007 by Elliott et al. This study refines and expands the guild approach for classifying fish estuarine use. The authors reorganize the estuarine usage functional group into four categories—marine, estuarine, diadromous, and freshwater—each containing multiple guilds. They standardize guild terminology, clarify amphidromy, and propose that estuarine species are either obligate or facultative users, with diadromous and estuary‑confined guilds obligate and marine/freshwater opportunistic guilds facultative.

Abstract

Abstract This study refines, clarifies and, where necessary, expands details of the guild approach developed by E lliott et al . (2007, Fish and Fisheries 8 : 241–268) for the ways in which fish use estuaries. The estuarine usage functional group is now considered to comprise four categories, that is, marine, estuarine, diadromous and freshwater, with each containing multiple guilds. Emphasis has been placed on ensuring that the terminology and definitions of the guilds follow a consistent pattern, on highlighting the characteristics that identify the different guilds belonging to the estuarine category and in clarifying issues related to amphidromy. As the widely employed term ‘estuarine dependent’ has frequently been imprecisely used, the proposal that the species found in estuaries can be regarded as either obligate or facultative users of these systems is supported and considered in the guild context. Thus, for example, species in the five guilds comprising the diadromous category and those in the guilds containing species or populations confined to estuaries are obligate users, whereas those in the marine and freshwater estuarine‐opportunistic guilds are facultative users.