Habitat complexity reduces the growth of aggressive and dominant brown trout (Salmo trutta) relative to subordinates

Environmental enrichment reduces aggression of pearl cichlid, Geophagus brasiliensis, during resident-intruder interactions

“…Territorial enrichment with physical barriers such as kelp models and pebbles can cause fish to have smaller individual territories with less visibility of surrounding habitat (Imre et al, 2002;Höjesjö et al, 2004). We suggest that reduced visibility of territory could increase energetic costs for resident animals when they attack an intruder and, thus, fish in this situation would either decrease aggressive interactions or choose co-habitation as their best strategy.…”

“…Nijman & Heuts (2000) found the effect in the cichlid, Haplochromis burtoni, however without showing an increase in aggressive interaction frequency. In contrast, environmental enrichment actually decreases aggression in rainbow trout (Imre et al, 2002) and brown trout (Höjesjö et al, 2004), although these studies did not perform tests within an owner-intruder paradigm. Accordingly, in rainbow trout greater environmental complexity leads to smaller individual territories, while in brown trout the subordinate fish have more protected area in an enriched environment.…”

“…Accordingly, in rainbow trout greater environmental complexity leads to smaller individual territories, while in brown trout the subordinate fish have more protected area in an enriched environment. Höjesjö et al (2004) suggested that dominant fish likely had less visual perception of opponents from a higher amount of enrichment-produced physical barriers and, therefore, attacked less frequently than when the physical barriers were absent.…”

Why Do Some Fish Fight More than Others?

“…In brown trout, dominant fish grow faster and survive better than subordinates in a simple habitat, but the converse is true in a more complex habitat ( fig. 5; Höjesjö et al 2004).…”

What tunes aggression in fish during fighting in environments that vary in enrichment?

“…Even then, our conclusion regarding the EE and aggression remains. Moreover, during our manuscript preparation and publication of our article (published in Neotropical Ichthyology Apr-Jun/ 2010 but online since Feb/2010), other reports were published that showed that EE reduces aggression or the territory size defended aggressively (leading to increased population density -cohabitation) in salmonids (Imre et al 2002;Höjesjö et al, 2004), and these reports were included in our article (Kadry & Baker, 2010). Heuts & Nijman (2011), however, arbitrarily restricted their analysis to cichlids and ignored those articles about salmonids and the article about convict cichlids (Archocentrus nigrofasciatus) by Barley & Coleman (2010).…”