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Resource partitioning facilitates the coexistence of sympatric species through spatial, temporal and/or trophic strategies. Fishes living in the intertidal zone demonstrate highly adaptive plastic behaviour, including resource partitioning, through spatial and temporal shifts in diet and microhabitat. Although intertidal fish assemblages are influenced by inter-and intraspecific competition, few studies have compared the extent of resource partitioning between sympatric species in the context of trophic niche plasticity. Here we used complementary approaches, stomach content and stable isotope (δ 13 C and δ 15 N) analyses, to evaluate seasonal and developmental shifts in trophic niche position in two sympatric (Favonigobius lentiginosus and Bathygobius krefftii) and one allopatric (Bathygobius cocosensis) species of intertidal goby. The results indicate that resource partitioning in the two sympatric species varied with season, with almost no trophic niche overlap in summer to about~30% overlap in winter. Also, evidence of dietary changes was found in B. cocosensis, which is likely associated with a shift in microhabitat and intraspecific competition. The findings highlight the temporal range of behavioural plasticity in trophic niche position of intertidal gobies, which likely has high adaptive value in the dynamic intertidal zone.

Translocation of fishes within and between drainage basins is widely recognised as a threatening process to Australian native fishes. While many translocations are deliberate, for example for fisheries enhancement, it is possible that translocation can occur naturally. In the Wet Tropic region of Australia, the widespread eastern rainbowfish, Melanotaenia splendida, has begun to colonise the Atherton tablelands. This is of particular concern because the area is home to several endangered endemic species such as the Lake Eacham rainbowfish, M. eachamensis, and its allies. It is likely that some of the translocations have occurred through the use of this species as bait, but the recent invasion of Lake Eacham may have occurred naturally via the movement of eggs between nearby streams running into Lake Tinaroo. Here we determine whether rainbowfish eggs could be transported over land by examining their desiccation tolerance. In the first experiment we plucked eggs from spawning media and exposed them to air for varying amounts of time. The results show almost 100% mortality after just 15 min. Rainbowfish eggs have a web-like projection that enables them to adhere to aquatic vegetation. In the second experiment, therefore, eggs were exposed to air attached to simulated weed (wet acrylic wool). Around 20% of eggs on the simulated weed where still viable after an hour. The results show that rainbowfish eggs could readily be transported between catchments by aquatic birds or human leisure activities such as kayaking or swimming. The implications for conservation management of Australian freshwater species is discussed.