Utility of direct observational methods for assessing competitive interactions between non‐native and native freshwater fishes

Abstract

Biological invasions are a major threat to global freshwater biodiversity. Competition is a frequent negative interaction between non‐native and native species, and this process is commonly quantified using indirect methods (e.g. dietary overlap, comparison of habitat use/selection). However, direct observation can provide crucial information on these biotic interactions. This paper reviews studies that used direct observational methods to quantify interactions between non‐native and native freshwater fishes. Although laboratory and field studies using direct observations are not common, both have been used to demonstrate impacts by non‐native species on native species. These effects include: (1) altered habitat selection and foraging behaviour and (2) disruption of reproductive behaviour. Direct observational techniques have great potential for quantifying the impacts of non‐natives on native freshwater fishes and can detect negative behavioural impacts that would be missed using indirect methods.

Environmental and economic impact assessment of alien and invasive fish species in Europe using the generic impact scoring system

“…). The eastern mosquito fish Gambusia holbrooki was the alien fish species with the highest competition impact (4.2 impact points) due to its negative influence on endemic cyprinids (Caiola & De Sostoa ; Almeida & Grossman ). Carassius auratus / C. gibelio achieved the highest impact points (3.6) on the ecosystem alteration category through an increased turbidity that resulted in a change of primary producers (Richardson et al.…”

“…Therefore, we assume that competition with native species plays a key role (average of 1.0 impact point per alien fish species in this category) and may still be underestimated. The most prominent example was Gambusia holbrooki (4.2 impact points), which is threatening IUCN Red Listed Iberian endemic fish species (Caiola & De Sostoa ; Almeida & Grossman ). Alien fish received the third highest impact points for ecosystem alteration.…”

Inter-population plasticity in dietary traits of invasive bleakAlburnus alburnus(Linnaeus, 1758) in Iberian fresh waters

“…Thus, strong invasive competitors such as the bleak usually displace native species from their ecological resources. For example, direct observations of bleak have shown how this fish can clearly disturb the foraging behaviour of the endemic cyprinid Parachondrostoma miegii (Steindachner, 1866) (Almeida & Grossman, ).…”

Cuckoldry features of introduced pumpkinseed sunfish (Lepomis gibbosus) in contrasting environmental conditions in southern Europe

“…The only potential evidence of cuckoldry behaviour from field studies comes from snorkelling surveys (Almeida and Grossman 2012) in which nesting (i.e., parental) males were observed until another individual with a similar size (i.e., a female) was allowed to approach the nest. In some occasions, smaller pumpkinseed approached the nest at the same time but were rebuffed by the nesting male.…”