Environmental Engineering Reference
In-Depth Information
Effects on coastal and estuarine fi shes
Nektonic communities (e.g., fish, squids and some large schooling
crustaceans) are usually less impacted by local changes in the coastal zone
due to their displacement ability, which enables them to migrate to other
areas where they fi nd optimum ranges in environmental parameters. That
explains why over the past few decades several changes in migration
patterns have been recorded (Roessig et al. 2004). However migration
to better grounds is not always the case and changes in environmental
parameters are known to have affected the spawning patterns and larval
drift of some species (Boesch 1999).
The general effect of projected human-induced climate change is that
due to global warming the distributional ranges of many species (both
terrestrial and marine) will move poleward from their current locations
or expand their ranges (Kennedy 1990, Gitay et al. 2002), although it is
impossible to make generalizations or reach a consensus on this respect.
Some fi sheries and aquaculture enterprises would benefi t from the results
of these range expansions, while others would most probably suffer losses
(Kennedy 1990); some assessments suggest that overall productivity will
be unaffected (Hall 2002) since local extinctions will generally be matched
by colonization of new areas (Thompson et al. 2002).
Fish communities are just one component of the coastal ecosystem
(probably the most important from a commercial viewpoint) and to
study the extent to which global changes impact them is not necessarily
a straightforward process. For example, Heath (2005) studied changes
in the food chain structure and function (with especial attention to fi sh
communities) for the North Sea for the past 30 years. He found that
fi shing pressure initially caused a change in fi sh secondary production.
Additionally, climatic variability for the North Sea combined with fi shing
pressure to produce shifts in the proportion of piscivorous to planktivore
fi sh species in a ~ 30 year period.
From the previous sections, it becomes apparent that the relationships
among processes and factors involved in global change and coastal marine
biodiversity are extremely complex. Figure 1 sumarizes the processes and
relationships treated in the above sections.
Concluding Remarks: What Until Now, What for the Future
For reasons concerning social, economic and cultural circumstances, it is
impossible to stop or revert the trends imposed by global change in the
past ~ 200 years. Steele (1998) mentions that there is no longer a choice
between pristine and managed coastlines, but only between priorities of
