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the target species has occasionally been studied; fish” (Pauly et al. 1998a). According to Pauly et
indirect effects have been largely neglected al. (1998a), this leads at first to increasing
(Smith 1995). Complex ecosystem dynamics catches, then to a phase of transition associated
and/or lack of research may hide cause-effect with stagnating or declining catches.
links, thus leaving room for continued overex- A striking intensification of world fisheries
ploitation. However, the unwise management of has been recorded since 1950, which corre-
resources has impacted the marine environment sponded to an increase in the proportion of re-
to the point that, today, everybody acknowledges sources subject to declines in productivity (FAO
the need for preservation of the remaining stocks 1997a). Recent reviews confirm that, worldwide,
(Kemp 1996). an estimated 44% of the major fish stocks are
fully exploited and are, therefore, producing
Fishery trends and the depletion of fish stocks, catches that have reached their maximum limit.
worldwide. Global totals of the amount of fish About 16% of fish stocks are overfished, and
caught during the past half-century provide a there is an increasing likelihood that catches
misleadingly reassuring view of the state of the might decrease if remedial action is not under-
world’s fisheries (Pauly et al. 2000). Most scien- taken to reduce or suppress overfishing. Another
tists now agree that the overall increase in the 6% appear to be depleted, and only 3% seem to
world fishery production should not be misunder- be recovering slowly (FAO 1998). A global pro-
stood for a healthy status of the marine resources. duction model showed that the demersal high-
The growth rate of the landings has actually de- value species were overfished and that a reduc-
clined steadily since 1950, and reached a plateau tion of at least 30% of fishing effort was required
at the beginning of the 1990’s (FAO 1994, to rebuild the resources. Given that few countries
1997a, 1998). have established effective control of fishing ca-
It has been pointed out that “aggregate land- pacity, around 60% of the major world fish re-
ings from various stocks which are the subject of sources are considered in urgent need of man-
a fishery-complex may continue to increase de- agement action (FAO 1994, 1997a). Such a pic-
spite local overfishing situations, as long as the ture is worsened by the fact that evaluating the
process of increase through expansion to new ar- impact of fishing activities on the marine envi-
eas and resource elements overshadows the proc- ronment is a difficult issue, as fishing trends are
ess of decrease through overfishing” (FAO routinely based on landing data (i.e., the catch
1997a). For instance, the increasing catch of brought to the fish market). Unfortunately, these
small pelagic species has masked the stagnation data are largely unreliable, as they are affected by
or impoverishment in take of demersal fish (FAO biases that cannot be estimated (Earle 1996). For
1997a, Pauly et al. 2000), and it has been instance, the biomass of discarded fish – that can
2
stressed that “the world fish supply is increas- account for a very high percentage of the catch –
ingly relying on low value species, characterised is simply ignored.
by large fluctuations in year-to-year productivity, In conclusion, the available data on world
hiding the slow but steady degradation of the fishery trends show that marine resources have
demersal high value resources” (Garcia and New- been exploited beyond reasonable limits and to
ton 1994). levels deemed unsustainable in most areas (Earle
Despite increased fishing effort, landings of 1996, Kemp 1996, Caddy et al. 1998, Christen-
some of the most important demersal fish (in- sen and Pauly 1998, Pauly et al. 1998a, Pauly et
cluding Gadus sp., Merluccius sp., al. 2000). In a recent article on Science - co-
Melanogrammus sp.) decreased from 5 million authored by 19 scientists - it was concluded that
tonnes in 1970 to 1.6 million tonnes in 1993, “ecological extinction caused by overfishing pre-
forcing the fishing industry to target other pelagic
species on a lower trophic level, such as Trachu-
rus capensis and Engraulis encrasicholus (FAO 2 A global assessment of fisheries bycatch and discards accounted
1994). At a global level, the phenomenon has for 33% (range 22-47%) of the total landings (Alverson et al. 1994),
and it has been pointed out that the sum of fishery-related mortali-
been described as “fishing down marine food ties occurring as a result of harvesting often involves a significant
webs”, which refers to “a gradual transition in number of fish in addition to catch and discard, fishing mortality
landings from long-lived, high trophic level, pis- being the aggregate of all catch mortalities including discard, illegal
fishing and misreporting (Alverson and Hughes 1996). For accounts
civorous bottom fish toward short-lived, low tro- of bycatch rates and discards in Mediterranean trawling fisheries see
phic level invertebrates and planktivorous pelagic for instance Carbonell et al. (1998), Stergiou et al. (1998),
Vassilopoulou and Papaconstantinou (1998).

Cetaceans of the Mediterranean and Black Seas – 9.10