The detail with respect to species definition in the reported statistics has shown some improvement, although it is still far from adequate as shown, for example, by the very large quantities reported as unspecified marine fish (Figure 3). The apparent increase in the diversity of species being landed may reflect real diversification in exploitation or changes in landing practices (reflecting changes in markets and prices), or it may be due to improvements to the reporting system itself. The changes due to improved reporting have probably been more important for secondary species than for the main market species, except perhaps at the beginning of their development process. For this reason, the following analysis of development phases was restricted to marine fish which account for the major share of the overall world production and its variation and because, in this sector, the confusion with aquaculture production is minimal.
The top 200 species-area combinations used for the analysis, referred to here as resources, were selected for analysis on the basis of average landings over the whole time period. These 200 major resources account for 77% of world marine fish production. The data set includes many species aggregates for items for which data were not collected for individual species, typically when species are landed unsorted and no sampling of species composition is made. These species aggregates have been excluded from the analysis except where the grouping is confined to a single genus (e.g. Cape hakes; Merluccius capensis and M. paradoxus). The 200 time series available for the top resource elements were processed in two ways, individually and as clustered groups.
Analysis of individual time series
The data were first standardised by rescaling each time series so that its mean equalled zero and standard deviation (SD) equalled 1. Then, by comparing the data available in every two consecutive years of each time series, each resource-year element in the data set was placed in one of three categories increasing, little change or decreasing landings (between the two years considered) depending on whether the slope of the series between the two years considered was, respectively, more than 0.05, between +0.05 and -0.05, or lower than -0.05.
Figure 24 shows the proportions of the 200 top world resources falling into each of these three categories. The proportion increasing grew until about 1965 and stabilised since then, while the proportion decreasing kept increasing throughout most of the time period. The proportion with little change diminished by a factor of 3-4 during the period. This category of stable landings corresponds to either a latent undeveloped phase of a fishery before it starts growing (Phase I) or to stabilisation at mature exploitation (Phase III), or in a few cases to a low level after a fishery has collapsed. The decrease in the frequency of occurrence of this little change category with time indicates clearly a reduction of fisheries in both undeveloped and mature phases. This illustrates the increased dynamics in the world fisheries with time, and their tendency to fall into two main categories: in expansion or in decline9.
9 It is worthwhile recalling that in meta-fisheries, an apparent global expansion may hide local crises and that global crisis may hide some local succesful developments or management.Figure 24. Percentage of major marine fish resources showing increases, little change and decreases in landings by year
Clustering of time series
In order to investigate further the exploitation pattern of these major resources and identify their present state of development, the 200 time series were grouped according to their shapes on an empirical basis, with no a priori specification of shape patterns. For the purpose, we used the Oblique Principal Component Cluster Analysis as implemented in the SAS procedure VARCLUS (SAS 1989), with default settings. Such clustering is based on the correlation matrix which gives equal weighting to each resource and so is independent of the magnitude and variance of production and facilitates comparison of time series profiles independent of scale.
Eight clusters or groups of resources were identified through the procedure. The proportion of the variation explained by the clusters ranged from 0.80 (cluster 1) to 0.46 (cluster 7), with the proportion of the total variance explained by eight clusters equal to 0.66. Some of the clusters were further divided between a majority group of resources positively correlated (denoted P) and a minority group, negatively correlated with the majority group (denoted N). Table 4 summarises the groups characteristics and shows the landings trend profiles (average standardised landings with fitted polynomials; see below) for the various groups of resources identified by the cluster analysis and which can be considered as parts of the overall fishery development model described above. The sequence of presentation in Table 4 roughly corresponds to a progression from early to late stages of the fishery development model, except for the last four groups which, with their oscillatory appearance, are typical of regime-driven stocks and more difficult to relate a priori to a particular phase of the development model.
Table 4: Landings trend profiles of eight groups of resources resulting from cluster analysis of production time series of the top 200 resources, further separated between the majority in a group (denoted by P) and the minority which are inversely correlated with the majority (denoted by N). The sequence of presentation roughly corresponds to the development phases of a typical fishery on a stock, except for the last four which are more typical of regime-driven stocks.
Group |
No. of |
Landings trend: average standardised |
Major resources in group |
|
8P
|
13
|
|
Largehead hairtail |
Pacific, NW |
Japanese anchovy |
Pacific, NW |
|||
Scads |
Pacific, W Cent. |
|||
Atlantic horse mackerel |
Atlantic, NE |
|||
Bombay-duck |
Indian Oc., W |
|||
Araucanian herring |
Pacific, SE |
|||
Indian mackerel |
Indian Oc., W |
|||
Daggertooth pike conger |
Pacific, NW |
|||
Greenland halibut |
Atlantic, NW |
|||
Common sole |
Atlantic, NE |
|||
1P
|
40
|
|
Chilean jack mackerel |
Pacific, SE |
Skipjack tuna |
Pacific, W Cent. |
|||
Indian mackerels |
Pacific, W Cent. |
|||
Yellowfin tuna |
Pacific, W Cent. |
|||
Pacific cod |
Pacific, NW |
|||
Scads |
Pacific, NW |
|||
Pacific cod |
Pacific, NE |
|||
Croakers, drums |
Indian Oc., W |
|||
Round sardinella |
Atlantic, E Cent. |
|||
Skipjack tuna |
Indian Oc., W |
|||
3P
|
37
|
|
Alaska pollock |
Pacific, NW |
Alaska pollock |
Pacific, NE |
|||
Gulf menhaden |
Atlantic, W Cent. |
|||
Sandeels |
Atlantic, NE |
|||
European pilchard |
Atlantic, E Cent. |
|||
Cape horse mackerel |
Atlantic, SE |
|||
Argentine hake |
Atlantic, SW |
|||
European pilchard |
Mediterranean |
|||
Chub mackerel |
Pacific, SE |
|||
Yellowfin tuna |
Pacific, E Cent. |
|||
2P
|
31
|
|
Capelin |
Atlantic, NE |
Chub mackerel |
Pacific, NW |
|||
Atlantic mackerel |
Atlantic, NE |
|||
Saithe |
Atlantic, NE |
|||
European sprat |
Atlantic, NE |
|||
Norway pout |
Atlantic, NE |
|||
Southern African anchovy |
Atlantic, SE |
|||
Jack and horse mackerels |
Atlantic, E Cent. |
|||
Sardinellas |
Atlantic, E Cent. |
|||
Indian oil sardine |
Indian Oc., W |
|||
4P
|
19
|
|
Anchoveta |
Pacific, SE |
Cape hakes |
Atlantic, SE |
|||
Haddock |
Atlantic, NE |
|||
Atlantic herring |
Atlantic, NW |
|||
Whiting |
Atlantic, NE |
|||
European plaice |
Atlantic, NE |
|||
Silver hake |
Atlantic, NW |
|||
Cunene horse mackerel |
Atlantic, SE |
|||
Atlantic mackerel |
Atlantic, NW |
|||
Amer. Plaice |
Atlantic, NW |
|||
5P
|
9
|
|
Atlantic cod |
Atlantic, NW |
Pacific herring |
Pacific, NW |
|||
Large yellow croaker |
Pacific, NW |
|||
Picked dogfish |
Atlantic, NE |
|||
Greater lizardfish |
Pacific, NW |
|||
Albacore |
Atlantic, NE |
|||
Jack and horse mackerels |
Mediterranean |
|||
Atlantic wolffish |
Atlantic, NE |
|||
Southern bluefin tuna |
Indian Oc., E |
|||
1N
|
2
|
|
Atlantic cod |
Atlantic, NE |
Pacific jack mackerel |
Pacific, E Cent. |
|||
3N
|
5
|
|
Atlantic herring |
Atlantic, NE |
Pacific herring |
Pacific, NE |
|||
European hake |
Atlantic, NE |
|||
Haddock |
Atlantic, NW |
|||
Skates |
Atlantic, NE |
|||
6N
|
9
|
|
Southern African pilchard |
Atlantic, SE |
Atlantic redfishes |
Atlantic, NW |
|||
Yellow croaker |
Pacific, NW |
|||
Pacific Oc. Perch |
Pacific, NE |
|||
Albacore |
Pacific, NW |
|||
E Pacific bonito |
Pacific, SE |
|||
European anchovy |
Atlantic, NE |
|||
Frigate and bullet tunas |
Pacific, NW |
|||
Red hake |
Atlantic, NW |
|||
6P
|
17
|
|
Japanese pilchard |
Pacific, NW |
South American pilchard |
Pacific, SE |
|||
Blue whiting |
Atlantic, NE |
|||
Atlantic redfishes |
Atlantic, NE |
|||
California pilchard |
Pacific, E Cent. |
|||
Filefishes |
Pacific, NW |
|||
Threadsail filefish |
Pacific, NW |
|||
Saithe |
Atlantic, NW |
|||
Mediterranean horse mackerel |
Mediterranean |
|||
European sprat |
Mediterranean |
|||
7N
|
7
|
|
European anchovy |
Mediterranean |
Californian anchovy |
Pacific, E Cent. |
|||
Sardinellas |
Atlantic, SE |
|||
Skipjack tuna |
Pacific, E Cent. |
|||
Atlantic menhaden |
Atlantic, W Cent. |
|||
Flathead grey mullet |
Pacific, NW |
|||
Common dab |
Atlantic, NE |
|||
7P
|
6
|
|
Pacific saury |
Pacific, NW |
Japanese jack mackerel |
Pacific, NW |
|||
European pilchard |
Atlantic, NE |
|||
Yellowfin tuna |
Pacific, NW |
|||
Bigeye tuna |
Pacific, NW |
|||
Pacific halibut |
Pacific, NE |
- In the 1950s and 1960s: Group 1N including Atlantic cod (Atlantic, Northeast) and Pacific jack mackerel (Pacific, Eastern Central);Figure 25. Total marine fish landing composition according to clustered groups of resources- In the 1960s: Group 4P including anchoveta (Pacific, Southeast), Cape hakes (Atlantic, Southeast), haddock (Atlantic, Northeast), Atlantic herring, silver hake, Atlantic mackerel, and American plaice (Atlantic, Northwest), whiting and European plaice (Atlantic, Northeast), and Cunene horse mackerel (Atlantic, Southeast);
- In the 1970s: Group 2P including capelin, Atlantic mackerel, saithe, European sprat, Norway pout (Atlantic, Northeast), chub mackerel (Pacific, Northwest), southern African anchovy (Atlantic, Southeast), jack and horse mackerels and sardinellas (Atlantic, Eastern Central), Indian oil sardine (Indian Ocean, Western);
- In the 1980s: Group 6P including Japanese pilchard, filefishes, threadsail filefish (Pacific, Northwest), South American pilchard (Pacific, Southeast), blue whiting and Atlantic redfishes (Atlantic, Northeast), California pilchard (Pacific, East Central), saithe (Atlantic, Northwest), horse mackerel and European sprat (Mediterranean); and
- In the 1990s: Group 1P including Chilean jack mackerel (Pacific, Southeast), skipjack tuna, Indian mackerels, yellowfin tuna (Pacific, Western Central), Pacific cod, scads (Pacific, Northwest), Pacific cod (Pacific, Northeast), croakers, drums (Indian Ocean, Western), round sardinella (Atlantic, Eastern Central), and skipjack tuna (Indian Ocean, Western).
Analysis of clustered group landings profiles
The average standardised landings series for each cluster was fitted with polynomial functions of varying degrees. The degree was selected subjectively for each line, as the lowest degree producing an apparently acceptable fit. Calculating the slope of the fitted line for every successive pair of years, the curves were sliced into segments corresponding to phases of increase, little change or decrease in reported landings where slopes were, respectively, greater than 0.05, between +0.05 and -0.05 and less than -0.05. It was assumed that the phases of increase or decrease corresponded respectively to developing (Phase II) and senescent (Phase IV) stages of fisheries development in the model (Figure 23). The phases with little change were further characterised as corresponding to high exploitation mature (Phase III) or undeveloped (Phase I), depending on whether or not the observed period of little change followed a period of increase. In a few cases a period of little change followed a period of marked decline and these were classified as senescent (Phase IV). Knowing what and how many resources are underlying each profile, the total number (and percentage) of resources in each phase can be calculated each year, across the whole data set. The overall pattern is shown in Figure 26.
Figure 26. Percentage of major marine fish resources in various phases of fishery development
By considering the worlds 200 most important resources in terms of landings and by aggregating them into a few families with similar trend patterns, the stages of development of fisheries on the various groups of resources become evident. This simple analysis shows strikingly the fact that there is very little room for further expansion of harvest from marine fish stocks and that further development of fishing effort will only result in lower catch rates. It illustrates vividly the large proportion of world resources which are subject to declines in productivity (senescent or Phase IV) and their increase with time. It also underlines the fact that the ever growing total tonnage of world fishery production gives a misleading vision of the state of world fishery resources and a false sense of security (a comment already made by Garcia and Newton, 1994). Unfortunately, a similar comment should probably be made for total aggregated landings at national level, so often used as a justification for further development.
The results shown for 1994 (i.e. the last data point available on Figure 26), indicate that about 35% of the 200 major fishery resources are senescent (i.e. showing declining yields), about 25% more are mature (i.e. plateauing at a high exploitation level), 40% are still developing, and 0% remain at low exploitation (undeveloped) level, although it must be remembered that the basis for the classification according to these phases is somewhat subjective. Given that few countries have established effective control of fishing capacity, this means that 60% of the major world fish resources are either mature or senescent and in urgent need of management action to halt the increase in fishing capacity or to rehabilitate damaged resources. A strikingly similar conclusion was reached by Garcia and Newton (1994), based on the information compiled by FAO on the state of stocks for which formal assessments are available, which concluded that 44% of the stocks were intensively to fully exploited, 16% were overfished, 6% depleted, and 3% slowly recovering, concluding therefore that 69% of the known stocks were in need of urgent management. That same study, using a global production model, with estimates of the world capacity, concluded that the demersal high value species were overfished and that a reduction of at least 30% of fishing effort was required to rebuild the resources.