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Variation in brown trout (Salmo trutta L.) population recruitment and structure is related to migratory patterns, which should depend on ease of access to habitats providing increased opportunity for growth. We quantified the number of young of year (YOY) as a proportion of the total number of brown trout at 24 locations on 11 streams within the Taieri catchment, New Zealand, including back calculated growth rates and emergence dates from otoliths. Locations with high absolute and relative abundance of YOY fish were related to elevation and distance from the river mainstem (habitat used by migratory fish), fish density, and the interaction between invertebrate food biomass, distance and elevation. Hatch date and growth were not related to the proportion of YOY fish, though growth was negatively correlated to total fish density. We suggest landscape features play a large role in determining recruitment and population structure. Locations at lower elevations have a high YOY density, high competition and lower growth, likely prompting out‐migration. These conditions could be created by successful return migration and spawning of large fecund fish resulting in YOY densities exceeding the habitat carrying capacity. Environmental factors, such as food availability, also played a role in determining population structure. These results provide an example of how population structure and recruitment might be controlled by local conditions and access to high growth environments in wild populations of introduced brown trout across a catchment. [ABSTRACT FROM AUTHOR]

Identifying the environmental factors that affect freshwater fish can be crucial for their conservation and management. Despite the widespread investigation of relationships between fish habitat use and environmental variables, there is a paucity of knowledge on how abiotic and biotic factors jointly influence stream fish habitat use. Three New Zealand South Island streams were selected to investigate the habitat preference of a stream-dwelling galaxiid, banded kokopu ( Galaxias fasciatus). Fish abundance in several permanent pools was determined by spotlighting at night once a month from June 2008 to May 2009. Drifting invertebrates and key physical features of each pool were measured at the time of fish sampling. An information-theoretic approach ( AIC) indicated that the most parsimonious candidate model to predict banded kokopu biomass was the one that included pool area, undercut banks, water velocity, overhanging vegetation, invertebrate drift density and an interaction term between invertebrate drift density and water velocity. Banded kokopu biomass was positively related to pool area, undercut banks, overhanging vegetation and invertebrate drift density. Our study suggests that fish resource use patterns need to be understood in the context of multiple interacting ecological factors, including prey abundance. [ABSTRACT FROM AUTHOR]

The availability of food, and hence energy, is known to influence the abundance, habitat choice and growth of individuals. In contrast, there is a paucity of knowledge on how the interaction of energy supply and social status determines patterns of residency and movement. This study tests whether the presence of conspecifics and an individual's social status in relation to food supply influence the fitness and movement of a drift-feeding fish ( Galaxias fasciatus). Using an information-theoretic approach (AIC), our analysis indicated that the most parsimonious model of fish movement among pools was one that included food supply, social rank and fish relative growth rate. Our results indicated that subordinate fish relocated more frequently compared to dominant fish, most likely as a consequence of intra-specific competition that limited the access of these smaller fish to resources and constrained their growth. Our results suggest that energy constraints may force individuals to explore new habitats in an effort to find more energetically profitable patches. We conclude that intra-specific competition mediated through the social hierarchy amongst closely interacting individuals plays a key role in determining individual growth, residency and relocation. [ABSTRACT FROM AUTHOR]

Resource availability and quality determine the distribution and community structure of animals in ecosystems. However, the balance between energy supply and energy consumption of species has received little attention because of the difficulty of estimating these factors. We measured the carrying capacity of a stream ecosystem in relation to the metabolic demands of Banded Kokopu (Galaxias fasciatus), a drift-feeding fish, to investigate the proportion of their energy budget met by the supply of their primary prey, drifting invertebrates. We sampled drifting invertebrates from multiple pools in 2 freshwater streams once a month over 1 y and measured their energy content. We used the energy content of individual invertebrates to estimate the total energy available in the form of drifting invertebrates in each pool. We measured fish O2 consumption rate (mg O2 kg-1 h-1) and converted it to metabolic demand (cal/h). Drifting aquatic invertebrates alone appear to be insufficient to meet Banded Kokopu energetic requirements in most seasons because the fish could obtain up to only 60% of their total energy expenditure from this food source. This result indicates that Banded Kokopu must access other sources of energy, such as benthic food items or terrestrial invertebrate inputs, especially during episodic events, and highlights the potential importance of terrestrial-aquatic exchange and other energetic subsidies. Our results suggest that food supply is likely to limit assemblages of drift-feeding fish and plays a key role in determining the outcome of intraspecific interactions, growth, movement, and the distribution of individuals within streams. [ABSTRACT FROM AUTHOR]

The article offers information on the study that focuses on the microhabitat use of a native New Zealand galaxiid fish, Galaxias fasciatus. It highlights the materials and methods used in the study including microhabitat use and availability, and data analysis. It also presents the results derived from the study with respect to fish frequency distribution, microhabitat occupied, and habitat availability.

A correction to the article "Does social status within a dominance hierarchy mediate individual growth, residency and relocation?" that was published in a previous issue is presented.