The evolution of aquaculture in the Mediterranean region: An anthropogenic climax stage?

Abstract

This study is the investigation of Mediterranean aquaculture complete history, from 1950 to 2020. Both functional than geographical expansion of aquaculture is investigated, considering two main complementary aspects of aquaculture: farmed species and farming countries. According to the models proposed in this research, Nile tilapia and Egypt will dominate the future of Mediterranean aquaculture. Malta and Israel are the first producer countries, in relative terms. The most pervasive species are European sea bass and gilthead sea bream that are promising for a future expansion. In several countries, aquaculture has huge potentiality of development and it could grow with a factor of 5 or more, based on the ratio capture vs fishery on country size. Aquaculture total production in 2020 was of 2.8 Mln tons and it is expected to reach from 3.65 Mln tons in 2030. Aquaculture will grow in the countries and species that in this moment are dominant and the future of Mediterranean aquaculture will be characterized by the affirmation of these ones.

Fig 1. Mediterranean aquaculture productions and annual growth rate from 1950 to 2020.

Fig 2. Mediterranean aquaculture economic value and annual growth rate from 1984 to 2020.

Dotted line: polynomial regression line, with equation and regression coefficients.

Fig 3. Fishery and aquaculture productions in the Mediterranean.

Black line, bottom: ratio aquaculture/fishery volumes. Dotted line, top: polynomial and linear regression lines, with relative equations and regression coefficients.

Fig 4. Capture fishery and aquaculture annual productions (considering only Mediterranean coastline of respective countries).

Fig 5. Cluster of main species of Mediterranean aquaculture, based on annual productions (calculated with Euclidean distances).

Fig 6. The main species farmed in the Mediterranean region, considering cumulate productions, number of countries where the species is farmed (diffusiveness) and number of years of farming (persistence).

Vertical line separates the species farmed from more than 60 years. Horizontal line separates species farmed in more than 20 countries.

Fig 7. Geographical expansion of main species farmed in the Mediterranean region.

Horizontal line indicates 15 countries. Geographical Expansion Rate (GER): annual expansion rate (%), calculated as average of the last 10 years 2017–2008. Blue histograms (positive GER) indicate species in geographical expansion; red histograms (negative GER) indicate species in geographical contraction.

Fig 8. Evolution of two main aquaculture sectors: Marine and freshwater aquaculture.

Fig 9. Evolution of two main aquaculture sectors: Marine and freshwater aquaculture: Annual growth rate.

Dotted lines: polynomial regression lines, with relative equations and regression coefficients.

Fig 10. Fish and bivalve farming in the Mediterranean region.

Fig 11. Fish and bivalve farming in the Mediterranean region: Growth rate.

Dotted lines: polynomial regression lines, with relative equations and regression coefficients.

Fig 12. Aquaculture productions of Nile tilapia.

Dotted lines: polynomial regression lines, with relative equations and regression coefficients.

Fig 13. Aquaculture productions of mullets.

Dotted lines: polynomial regression lines, with relative equations and regression coefficients.

Fig 14. Aquaculture productions of gilthead seabream.

Dotted lines: polynomial regression lines, with relative equations and regression coefficients.

Fig 15. Aquaculture productions of European sea bass.

Dotted lines: polynomial regression lines, with relative equations and regression coefficients.

Fig 16. Heatmaps of main aquaculture species in the Mediterranean: Original data.

Fig 17. Heatmaps of main aquaculture species in the Mediterranean: Scaled data.

Data scaling: x _scaled = (x-μ)/s.d. (μ = mean; s.d. = standard deviation).

Fig 18

Comparison between succession of farmed species in the Mediterranean in 3 stages (A and C) and a forest succession in 6 stages (B).

Fig 19. Aquaculture diversity in the Mediterranean region, considering its main components: Main, relevant and minor species.

A: Pareto Index trend (ratio main/relevant species).

Fig 20. Aquaculture diversity in the Mediterranean region, considering its main components: Main, relevant and minor species: Evolution of different components.

Dotted lines: polynomial regression lines, with relative equations and regression coefficients.

Fig 21. Aquaculture diversity in the Mediterranean region.

Shannon Index and species richness.

Fig 22. Geographical map of aquaculture of Mediterranean aquaculture*.

(A, cluster obtained considering the entire period; B, cluster obtained considering las 5 years). * Data from parts of the countries on Atlantic Ocean or Red sea coasts (France, Morocco, Spain and Egypt) have been excluded by geographical analysis.

Fig 23. Aquaculture value (blue line) and GDP pro capita (black line) in Egypt.

In the corner, on the left, the Pearson correlation coefficient (r).

Fig 24. Aquaculture value (blue line) and GDP pro capita (black line) in the zone 2 (Fig 22).

In the corner, on the left, the Pearson correlation coefficient (r).

Fig 25. Aquaculture value (blue line) and GDP pro capita (black line) in the zone 3 (Fig 22).

In the corner, on the left, the Pearson correlation coefficient (r).

Fig 26. Aquaculture production (blue line) and sea food* consumption pro capita (kg/year) (black line) in Egypt.

In the corner, on the left, the Pearson correlation coefficient (r). (*sea food includes: cephalopods, crustaceans, demersal fish, fish body oil, fish liver oil, freshwater fish, marine fish, other molluscs, other pelagic fish, according all the items contained in the database: https://www.fao.org/faostat/en/#data/CL).

Fig 27. Aquaculture production (blue line) and sea food* consumption pro capita (kg/year) (black line) in the zone 2 (Fig 22).

In the corner, on the left, the Pearson correlation coefficient (r). (*sea food includes: cephalopods, crustaceans, demersal fish, fish body oil, fish liver oil, freshwater fish, marine fish, other molluscs, other pelagic fish, according all the items contained in the database: https://www.fao.org/faostat/en/#data/CL).

Fig 28. Aquaculture production (blue line) and sea food* consumption pro capita (kg/year) (black line) in the zone 3 (Fig 22).

In the corner, on the left, the Pearson correlation coefficient (r). (*sea food includes: cephalopods, crustaceans, demersal fish, fish body oil, fish liver oil, freshwater fish, marine fish, other molluscs, other pelagic fish, according all the items contained in the database: https://www.fao.org/faostat/en/#data/CL).

Fig 29. Maximum diversity map (Shannon index) based on maximum values out of 67 years in each country.

Fig 30. Maximum diversity map (number of species) based on maximum values out of 67 years in each country.

Fig 31. Map aquaculture persistence (years of farming in each country) *countries corresponding to ex-Yugoslavia have been counted considering the historic change of national boundaries.

Fig 32. Geographical expansion of aquaculture in the Mediterranean region.

In red the number of countries producing the 80% of annual production. Pareto index (%) = (number of countries producing the 80% of annual production/total countries aquaculture producing).

Fig 33. Aquaculture productions in Egypt (main species) from 1950 to 2020 (annual %).

Fig 34. Aquaculture productions in Egypt (main species) from 1950 to 2020.

Fig 35. Aquaculture and fishery production in Malta from 1950 to 2020.

Black lines are the aquaculture/fishery volume ratio.

Fig 36. Aquaculture and fishery production in Israel from 1950 to 2020.

Black lines are the aquaculture/fishery volume ratio.

Fig 37. Aquaculture and fishery production in Egypt from 1950 to 2020.

Black lines are the aquaculture/fishery volume ratio.

Fig 38. Multiple correlation chart: Considering all the countries.

Countries are categorized into three main groups: high, medium and low production. Diversity (maximum number of farmed species); Persistence (maximum number of years of farming); aquaculture production (cumulate production on the last 5 years); country size (square km). Lower part of diagram: Pearson correlation coefficients (with size of character proportional to value); on the diagonal: frequency histogram of considered variable; upper part of diagram: scatterplots of countries divided into 3 categories, by production: [red dots (>1.5 Mln tons); green dots: (>0.5 and < 1.5 Mln tons); purple dots (<0.1 Mln tons) and regression line (dotted line)].

Fig 39. Multiple correlation chart: Excluding Egypt.

Countries are categorized into three main groups: high, medium and low production. Diversity (maximum number of farmed species); Persistence (maximum number of years of farming); aquaculture production (cumulate production on the last 5 years); country size (square km). Lower part of diagram: Pearson correlation coefficients (with size of character proportional to value); on the diagonal: frequency histogram of considered variable; upper part of diagram: scatterplots of countries divided into 3 categories, by production: [red dots (>1.5 Mln tons); green dots: (>0.5 and < 1.5 Mln tons); purple dots (<0.1 Mln tons) and regression line (dotted line)].