Through analysing the methodologies and findings of research on temperate, demersal fish habitat requirements to highlight the main developments in this field and to identify
potential shortfalls.
Many studies were undertaken over large spatial scales
(100s km2) and these generally correlated abundances of fish to abiotic variables.
Biological variables were accounted for less often.
Small spatial scale (m2), experimental studies were comparatively sparse and commonly focused on biotic
variables. Whilst the number of studies focusing on abiotic variables increased with
increasing spatial scale, the proportion of studies finding significant relationships between habitat and fish distribution remained constant. This mismatch indicates
there is no justification for the tendency to analyse abiotic habitat variables at large
spatial scales.
Conclusion
Determining the habitat requirements of demersal
fish species is inherently difficult because of the
complex nature of marine ecosystems, the multiple
factors affecting fishhabitat associations, the range
of scales over which they act and the general
difficulties of sampling marine habitats. Defining
fishhabitat relationships will, however, be one of
the necessary steps towards the advocated ecosystem-based approach to fisheries management and
the sustainable exploitation of demersal fish stocks.
Many developments in techniques and technologies
show promise in elucidating the complex interactions between demersal fishes and their habitat. The
successful application of such developments will,
however, strongly rely on the quality of the data
used combined with understanding of the fundamental ecology of the systems and species under
study (Austin 2007). Where possible, it will therefore be advantageous to test habitat variables under
controlled experimental conditions (i.e. small-medium spatial scales), building results from such
studies into larger scale models.
Our analysis highlights some important trends in
the field of demersal fish habitat determination.
The reasons behind the focus on larger scales are
no doubt a result of a combination of factors. It is,
however, clear that to advance the field, there should
be a move towards the investigation of abiotic
variables at smaller spatial scales as well as increased
attention to the analysis of biotic habitat variables
over all spatial scales of study.
This will help describe
distributions determined by abiotic habitat variables
that may act over small spatial scales not previously
considered and allow biotic-based causal relationships to be better explained. It will therefore be
necessary to invest in the implementation of more,
smaller spatial scale data collections or alternatively
increase the resolution of larger spatial scale data
sets. Work investigating the power of monitoring
surveys to detect trends in abundance (e.g. Blanchard et al. 2008) will therefore prove invaluable in
the design of future studies and surveys.
Defining temporal aspects of habitat will also
prove valuable in advancing ecological understanding of the species under study. The inclusion of
longer time scales and the consideration of temporal
differences in habitat use may also provide important information on the cumulative effects of
human-induced impacts, the overall status and
recovery of impacted systems and increase capabilities to predict future change of the species or system
under study (Hewitt et al. 2001). We argue that
through attention to the areas highlighted herein,
along with more holistic definitions of habitat,
researchers are likely to be better equipped to
inform management at a range of spatial and
temporal scales.
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