Analysis of production peaks

The sequence of production peaks reached by each species or species group can be used to identify the different phases of the development of each fishery (FAO, 1996). The results of this analysis for Cuban fisheries are summarized in Table 1. This table shows the sequence of attainment of peak landings in a smoothed time series by five-year running-means. The procedure for smoothing the original time series has the effect of reducing, but not completely eliminating, the potential impact of interannual environmental changes on natural populations.

The sequence of peaks is generally as would be expected, based on knowledge of fisheries development in Cuba. With the exception of small tunas (skipjack and blackfin tuna mainly), whose peaks occurred at the end of the 1950s, most of the peaks occurred in the 1970s and 1980s with only one group, the mojarras, reaching a peak in the 1990s. The last column of Table 1 lists the ratio between recent landings (1995) and maximum landings. Only the turkey wing clam and the mojarras (two species that have been exploited only relatively recently) show recent landings that are above the peak landings on a five-year running mean. Grunts, spiny lobster, porgies and thread herring landings have fallen by less than 25 percent, but shrimps, mullets, gray snappers and Nassau grouper have fallen by around 75 percent, or even more, in the last two decades. All the other species or species groups, such as small tunas, yellowtail snapper, lane snapper, mutton snapper, Spanish mackerels, scaled sardines, sharks and jacks, have fallen by between 40 and 70 percent. The overall fall is 40 percent, considerably higher than the 22 percent calculated by Grainger and Garcia (FAO, 1996) for world demersal resources.

TABLE 1

* Although the land crab is a terrestrial species, its fishery is based completely on its annual migration to the sea during the reproductive season.

Although the differences between peak and current landings must be interpreted with caution, as pointed out by Grainger and Garcia (FAO, 1996), peaks in smoothed time series probably give an indication of the average long-term yield that the species assemblage in a given area may be able to sustain in the future if properly managed and if there are no significant causes of disturbance for the fisheries. The sum of the differences between the observed historical peak landings of each species or species group, smoothed by a five-year running-mean, and recent landings, amounts to about 20 000 tonnes. This observation implies that, if these individual species or species groups were all restored to their historical maximum levels, a gain of some 20 000 tonnes of landings could be expected. However, some declines may reflect potentially irreversible situations created by habitat losses in the coastal zone caused, in turn, by the impact of human activities or by other environmental changes.