Evaluation of Sustainable Utilization of African Marine Fishery Resources

Abstract

Sustainable utilization evaluation is the basis for ensuring the sustainable exploitation of fisheries’ resources. This paper explores the changes in the mean trophic level of African marine fish catches during a 70-year period based on the statistical data on marine fisheries’ catches in Africa from 1950–2019, provided by the FAO in, order to determine the sustainable utilization of Africa’s fishery resources. The results indicate that although the marine fishery resources of African coastal countries have great variability, their exploitation has roughly gone through the stages of under-exploitation, rapid exploitation, and over-exploitation. Currently, marine fisheries in North and Central Africa are characterized by sustainable exploitation, while East, West, and Southern Africa are in a state of overfishing. The study implicates that African countries should establish a real-time monitoring system for marine fishery resources as soon as possible in order to dynamically grasp the actual changes in fish community structure due to fishing activities, ensure transparency in management and decision making, enact marine regulations to restrict massive fishing by overseas fleets, issue fisheries licenses cautiously, adopt conservative resource conservation policies, and enforce actions to achieve sustainable fisheries development.

1. Introduction

Almost half of the world’s population’s livelihood depends on the ocean [1]. Marine fishery resources are an important component of natural resources and one of the most important sources of human food, providing 40% of the protein for 2/3 of the world’s population [2]. Africa is bordered by the Indian Ocean to the east, the Atlantic Ocean to the west, the Red Sea and the Suez Canal to the northeast, and the Strait of Gibraltar and the Mediterranean Sea to the north, with a coastline of 32,000 km. Its natural geographical conditions make Africa rich in marine fishery resources, and the fisheries of the entire continent are also dominated by marine fishing. Fisheries play a key role in the economies and people’s lives of most African countries [3]. Thus, studying the current status of exploitation of marine fishery resources in Africa is of great significance for the future of fisheries and economic development of African countries.

According to SDG-14 of the 2030 Agenda, biodiversity loss is one of the current marine issues that are to be taken care of [1]. Since the 1950s, marine fishery resources have gradually transitioned from an underfished to overfished state. By the 1970s and 1980s, some major traditional fishery resources even began to decline. Consequently, marine research is the key element to protect ocean crisis. More efforts need to be dedicated to ocean research.

The emergence of the decline phenomenon sounded an alarm and drew widespread attention to the concept of the sustainable use of fishery resources. Scholars’ studies on the sustainability of marine fisheries in Africa have focused on the sustainability assessment of fishery stocks [4,5,6,7], sustainable fisheries governance [8,9,10,11,12,13,14], driving factors affecting fishery resources [15,16,17,18], illegal fishing [19,20,21], overexploitation [3,12,22,23], and sustainable policy implications [24,25,26]. The three conceptual pillars of (social, economic, and environmental) sustainability, which can be commonly represented by three intersecting circles with overall sustainability at the center, have impacts on each other [27]. The total productions of global marine fishery resources have declined gradually after reaching a peak in landings in 1996. Fishing not only reduces populations of target species but also alters the structure of ecosystem [28,29]. Not only can overexploitation cause negative ecological consequences, can it also reduce fish production, resulting in negative social and economic consequences [30,31]. Ecosystem-based approaches and models of fisheries management have been proposed in order to make fisheries resources which contribute to the economy and society in a sustainable manner. However, the concept of ecosystem health has been difficult to translate into the basis for fisheries management policy development [32]. According to the Agenda 2030 for Sustainable Development and SDGs [1,27], the paradigm of sustainable development includes the three Ps (people, planet, and profit), but also good governance, which is the basis of the 3 Ps, and without which all the contributions offered in the three dimensions become useless. However, good governance needs to be based on recent and complete data. Thereby, in recent years, the scientific and accurate monitoring and assessing changes in marine ecosystems have become central topics in marine science. Among them, the study of the mechanism of nutrient dynamics change is a crucial element to reveal the whole system change process. By analyzing changes in the ecological indexes TLm and FiB, the trends in fisheries’ catch data and their trophic levels can be accurately reflected, which is an important indicator for understanding changes in the structure and function of marine ecosystems [33,34,35]. Thus, TLm and FiB indexes are increasingly adopted by national organizations and groups as indicators of biodiversity levels and fisheries’ sustainability [35,36]. Currently, most of the relevant studies in academia have focused on the fishery resources of African-adjacent seas using TLm and FiB index of catches [37,38], but fewer studies have evaluated the exploitation of marine fishery resources in African coastal countries [39]. The study area is limited to certain marine areas with small spatial scales. Historical data are also limited to certain years with short time series. To fill these research gaps, this paper takes catch data and TLm and FiB indexes as indicators to assess the sustainable utilization of fishery resources, and evaluates the exploitation of marine fishery resources in five major regions of Africa (Figure 1) during 1950–2019.

This study illustrates the variation of catch data, TLm, and FiB index in Africa, discusses the results of assessment by region, and concludes with policy implications. This paper provides several contributions: (1) this study uses TLm and other indicators as a basis for formulating fisheries governance policies. By making an objective assessment of the sustainable utilization of marine fisheries resources in Africa, this paper contributes to providing a scientific basis for African fisheries’ managers and companies investing in fisheries in Africa to grasp the state of exploitation of marine fisheries’ resources in Africa and make rational decisions. (2) This research highlights the need to adopt fishery management policies and proposes policy implications for the sustainable development of marine fisheries in Africa from the perspective of good governance. It is hoped that these results could help in providing a reference for the future sustainable development of marine fisheries in Africa.

2. Data and Methods

2.1. Datasource

Since marine fishery resources are more obviously regional in nature, the development is uneven among regions. Therefore, this paper divides the study area into five major regions, namely North Africa, East Africa, Central Africa, West Africa, and Southern Africa, according to the traditional geographical division. The data for the marine fishery resources study were obtained from the FAO website and downloaded according to the ISSCAAP classification. Since this paper focuses on the effects of fishing activities on major fishery resources, aquatic plants, cetaceans, seals, other aquatic mammal species, and some miscellaneous fish species of unknown taxonomy were not counted. Trophic levels of species were obtained by consulting Fishbase’s ISSCAAP table (https://www.fishbase.se/report/ISSCAAP/ISSCAAPSearchMenu.php, accessed on 20 October 2022) and See Around Us Project Database (https://www.seaaroundus.org/data/#/eez, accessed on 20 October 2022). The trophic levels of the main catch species are listed in

Table 1. Trophic level values for the top 20 species (according to the catch data in the year 2019) used to compute mean trophic level.

Commen Name	Scientific Name	Trophic Level
Atlantic chub mackerel	Scomber colias	3.65
Bigeye grunt	Brachydeuterus auritus	3.03
Barracudas nei 1	Sphyraena spp.	4.32
Atlantic bumper	Chloroscombrus chrysurus	3.21
Bigeye tuna	Thunnus obesus	4.49
Atlantic bluefin tuna	Thunnus thynnus	4.43
Atlantic bonito	Sarda sarda	4.50
Albacore	Thunnus alalunga	4.31
Atlantic mackerel	Scomber scombrus	3.65
African sicklefish	Drepane africana	3.10
African moonfish	Selene dorsalis	4.08
Atlantic sailfish	Istiophorus albicans	4.50
Bearded brotula	Brotula barbata	3.78
Angolan dentex	Dentex angolensis	3.52
Atlantic pomfret	Brama brama	4.08
Anchovies, etc. nei	Engraulidae	3.28
Benguela hake	Merluccius polli	4.50
Amberjacks nei	Seriola spp.	4.34
Alexandria pompano	Alectis alexandrinus	3.60
Annular seabream	Diplodus annularis	3.40

Data sources: Fishbase’s ISSCAAP table (https://www.fishbase.se/report/ISSCAAP/ISSCAAPSearchMenu.php, accessed on 20 October 2022). ¹ nei means multispecies.

.

2.2. Mean Trophic Level

“Trophic level” (TL) represents the position of an organism in an ecosystem food chain/web and can be used to indicate either the ability of a given population to assimilate energy or the level of energy consumption of a large group of taxa. The concept of mean trophic level (TLm) of the fisheries catch data, was introduced in 1998 [33]. A high TLm index indicates a high level of marine biodiversity and of marine ecosystem integrity. Referring to Pauly et al. [33,34], the trophic level is defined as 1+ the mean trophic level of their prey. Based on this, the mean trophic level of the fisheries’ catch data was calculated by the following equation:

$$\mathrm{TLm}=\frac{{\sum }^{ }{\mathrm{TL}}_j{Y}_{ij}}{{\sum }^{ }{Y}_{ij}}$$

(1)

where, TLm is the mean trophic level in year, TL_j is the trophic level of catch species j, and Y_ij is the catch data of catch species j in year i.

Caddy and Garibaldi [37] believed that coastal eutrophication increases the annual catches of fishery resources at lower trophic levels, which makes the TLm decrease and is not conducive to analyzing the effects of fisheries on marine ecosystems, such as the Black Sea and the Mediterranean Sea, due to eutrophication that decreases the number of benthic fish and thus the mean trophic level. Therefore, to exclude the effect of eutrophication, Pauly et al. [40] proposed counting only the changes in mean trophic level of species with TL > 3.25. In this paper, the mean trophic levels of all species and species with TL > 3.25 were compared and analyzed.

When the TLm index is decreasing and catches of lower trophic level species are increasing, if the catches of higher trophic level species continue to decrease, it indicates that “fishing down food webs” is occurring. If the catches of higher trophic level species remain stable or gradually increase, it indicates the phenomenon of “fishing through food webs” [41].

2.3. Fishing-in-Balance Index

Caddy et al. [42] propose that the measurement of the TLm may overlook the fact that “fishing down food webs” may be a deliberate strategy to catch more fish, rather than a reflection of the depletion of the fishery. Likewise, bottom-up effects, where there is an increase in the production of species of low trophic level (e.g., due to eutrophication) but not necessarily a decline in species of high trophic level, may lead to an inaccurate perception of fishery depletion [43]. Therefore, in order to accurately assess the impact of fishing activities on marine fishery resources, it is necessary to not only rely on changes in the mean trophic level of the catch, but also to consider the Fishing-in-Balance index (FiB). The TLm index is complemented by the FiB index, which gives an indication of whether the fishery is ecologically balanced [44,45]. The FiB index is an indicator of trophic level balance in fisheries management developed by Pauly and Watson [40] to account for transfer efficiency between trophic levels and whether trophic level changes are matched by “ecologically correct” changes in catch.

The FiB index can assess whether the fishery is in ecological equilibrium [44]. The addition of the FiB index to the TLm model controls for changes in fishing strategy and the effects of geographic expansion of the fishery on TLm [44]. If either bottom-up effects occur, or if a geographic expansion of the fishery occurs, and the ecosystem that is exploited by the fishery has been in fact expanded, the FiB index will increase [46]. If the fisheries remove so much biomass from the ecosystem that its functioning is impaired, the FiB index will decrease [46]. The formula is as follows:

$$\mathrm{FiB}=\log \left[Y_i{\left(\frac{1}{\mathrm{TE}}\right)}^{{\mathrm{TL}}_i}\right]-\log \left[Y_0{\left(\frac{1}{\mathrm{TE}}\right)}^{{\mathrm{TL}}_0}\right]$$

(2)

where Y_i is the catch data in year i, TL_i is the mean trophic level of catch in year i, and TE is the transfer efficiency between trophic levels, which is set to 0.1 in this paper [44]; Y₀ is the catch data for the initial year of the time series, TL₀ the mean trophic level of that year [47]. FiB was determined considering: (a) a trophic efficiency of 0.092, which is the global average over a wide range of aquatic ecosystems [48] and, (b) the more widely used value of 0.1 [49]. Using either transfer efficiency value gave virtually the same FiB results; therefore, TE = 0.1 was used in order to facilitate comparison with other studies [45].

The FiB index remains constant when the decline in trophic level is offset by an increase in catch data. The FiB index increases when the rate of increase in catch data is greater than the rate of decrease in trophic level or when the fishing area expands. The FiB index decreases when the increase in catch data is slower than the decrease in trophic level [46]. If the TLm of catch increases with the increase in catch data and the FiB index also shows an increasing trend, it means the occurrence of the “fishing through food webs” phenomenon [33]. If the TLm of catch decreases with the increase in catch data and the FiB index also shows a decreasing trend, it means that the increase in catch data cannot compensate for the decrease in trophic level and the fishery resources are damaged, and the phenomenon of “fishing down food webs” occurs [33].

2.4. Temporal Trend (Slope)

The temporal trend (Slope) analysis can avoid the randomness and contingency of the research results. By fitting the data of all years, the regression slope of each variable can be obtained to reflect the linear relation of the attribute in each unit and time [50]. This paper uses this method to calculate the slope of catches, TLm and FiB, and analyzes their temporal trend. The formula is as follows:

$$\mathrm{Slope}=\frac{{\displaystyle {\sum }_{i=1}^n\left(i\cdot Y_i\right)-{\displaystyle {\sum }_{i=1}^{n}i{\displaystyle {\sum }_{i=1}^n{Y}_i}}}}{{\displaystyle {\sum }_{i=1}^n{i}^2-{\left({\displaystyle {\sum }_{i=1}^{n}i}\right)}^2}}$$

(3)

where Slope is the slope of the trend line, Y donates the attribute (catches, TLm and FiB) in each research unit, n is the time span (n = 70), and i is the time unit (year). If Slope > 0 or <0, it means the attribute presents an upward or downward trend, respectively, over time. If Slope = 0, it means the value of the attribute reflects basically no increasing or decreasing trend.

2.5. Pearson’s Correlation

This study tests the goodness of fit of linear regression with the help of the coefficient of determination R², so as to measure the appropriateness of a linear trend over time [51]. R² is calculated as follows:

$$R^2={\left(\frac{{\sum }_{i=1}^n\left(x_i-\overline{x}\right)·\left(y_i-\overline{y}\right)}{\sqrt{{\sum }_{i=1}^n{\left(x_i-\overline{x}\right)}^2}\sqrt{{\sum }_{i=1}^n{\left(y_i-\overline{y}\right)}^2}}\right)}^2$$

(4)

R² is the square of Pearson’s correlation with a maximum value of 1, n is time horizon (n = 70), and i is the annual variable. The closer the R² value is to 1, the better the regression line fits the observed values and the stronger the linear correlation between the variables.

3. Results

3.1. Variation of Marine Catch in Africa

After 70 years of development, marine catches in Africa have presented significant spatial and temporal differences. At the regional scale, marine fisheries’ catch data showed an upward trend in all regions of Africa except for Southern Africa (Figure 2). Among them, North Africa and West Africa had similar levels of marine fishing, with similar changes in marine catch and rapid development trends in marine fisheries. North Africa’s catch showed a rapid growth trend (Slope = 18404, R² = 0.91), from 156,000 t in 1950 to 1,316,000 t in 2019. The catch in West Africa increased rapidly from 51,000 t in 1950 all the way to 1,692,000 tons in 2019 (Slope = 21475, R² = 0.92). East and Central Africa had close levels of marine fisheries’ fishing. Although there was a gap compared to North and West Africa, they were also developing gradually. East Africa’s marine fisheries’ catch showed a flat growth trend (Slope = 3770, R² = 0.83), steadily increasing from 5000 t in 1950 to 333,000 t in 2019. Similar to East Africa, Central Africa’s marine catch has demonstrated an overall low and steady growth (Slope = 2808, R² = 0.35), increasing from 53,000 t in 1950 to 398,000 t in 2019. However, compared to East Africa, which has been growing at a low rate, Central Africa’s catches between 1957 and 1975 still had a slightly greater ups and downs.

Southern Africa has seen the most significant changes in marine fisheries’ catch, which grew rapidly between 1950 and 1970, far ahead of other regions in Africa. 1960s was the golden age of marine fisheries in Southern Africa, with an average annual catch of about 1,500,000 tons. However, after 1970, the marine fisheries in Southern Africa declined. In contrast to the accelerated development of marine fisheries in other regions of Africa, the marine catches of Southern Africa have been on a declining trend (Slope = −10836, R² = 0.34), and the current marine catches are much lower than those of North and West Africa, and are roughly close to the marine catch levels of East and Central Africa. In 2019, the marine catches of Southern Africa were only 530,000 tons, less than one-third of the marine catch of West Africa during the same period.

3.2. Changes of TLm in Different Regions of Africa

The trend in the TLm index has been increasing in all regions of Africa, except North Africa (Figure 3). The overall trends in the TLm and the ^3.25TLm indexes are consistent for North, Central, West, and Southern Africa, with the exception of East Africa, where the overall trends in the TLm and the ^3.25TLm indexes are reversed.

Both TLm indexes in Central Africa (Slope = 0.003, R² = 0.73) and West Africa (Slope = 0.002, R² = 0.63) showed a similar steady upward trend during 1950–2019. The TLm index in East Africa showed a downward trend (Slope = 1.84, R² = 0.4), while the ^3.25TLm index showed an upward trend (Figure 4b). Contrary to the trend of the TLm index in the other four regions, the TLm index in North Africa exhibited a sharp downward trend in general (Slope = −6.32, R² = 0.35).

At the regional scale, the TLm index in Africa also has significant spatial imbalance (Figure 5). The high TLm value areas gradually expanded over the period 1950–1980. Since 1980, the high value areas have been converging. During the study period, the distribution of the high and low TLm value areas in Africa changed constantly, with only the Horn of Africa region in East Africa maintaining consistently high TLm values.

3.3. FiB Induced by Marine Fishery Catch in Africa

Overall, the FiB index for all five regions in Africa showed an increasing trend during the study period (Figure 6).

At the regional scale, the spatial distribution of the FiB index in Africa presented significant regional heterogeneity and was concentrated in the contraction of low value areas and the expansion of high value areas (Figure 7). During the study period, the FiB index in Africa exhibited a significant upward trend. The high value areas are gradually concentrated in African countries along the Atlantic coast, particularly in West and Central Africa.

4. Discussion

Monitoring and exploring long-term trends in marine ecosystems has become a world topic of great interest. Marine ecosystems are an intrinsically interconnected and unified whole, and the TLm index is the basis for revealing ecosystem structure and function [52], and is a powerful indicator of marine ecosystem integrity and fisheries’ sustainability at the global and regional levels, with fluctuations in its value directly related to external disturbances to the ecosystem and naturally occurring shifts in environmental productivity [41,47,52,53]. This paper discussed the long-term variation of catch and TLm and FiB indexes in all five regions of Africa from a temporal and spatial perspective. The interpretation of the indicators is subjective and no limit values or reference points for the results obtained from these indicators have been established nationally or internationally. Therefore, this paper focused not on a particular value but on the trends of the indicators, so that the state of the marine ecosystem can be evaluated by observing the trends of the TLm and FiB indexes [54,55]. In addition, since the marine fishing industry is driven by profits, the TLm index could be sensitive not only to fishery-induced changes at the ecosystem level, but also to long-term environmental variation, and economic, technological, and cultural factors [37,42]. Based on this, this paper only discussed the case of measuring the sustainability level of marine fisheries based on catch data and TLm and FiB indexes.

4.1. North Africa

After being gradually exploited and then overexploited, marine fisheries in North Africa are now in a relatively good state of sustainable development. The major marine fishing countries in North Africa are Egypt, Libya, Morocco, and Algeria, and the main fish caught are Sardina pilchardus, Thunnus spp., and Sepia officinalis species.

The catch data in North Africa increased from 1950 to 1960. While the TLm index showed a decreasing trend, the FiB showed an increasing trend, suggesting that the fishery was expanding to stocks that were only lightly exploited [56]. The observed changes in catch data, FiB, TLm, and ^3.25TLm indexes during 1960–1980 indicate that marine biodiversity, as well as marine ecosystem integrity, were at high levels in North Africa during this period [33,35]. The strong and marked increase in catch data and FiB index and the marked decrease in TLm index from 1980 to 2000 indicate that the accelerated expansion of fishing areas led to a fishing down process in North Africa [56]. This may be related to the fact that North African countries started to strengthen their fisheries’ management during this period and formulated a series of fisheries policies to promote their fisheries’ development. For example, the Egyptian government has not only vigorously promoted the construction of fisheries research institutions (e.g., the Egyptian Agricultural Research Centre and the Abasa Fisheries Research Centre), but has also closely integrated fisheries’ research and extension in an attempt to effectively promote the transformation of scientific and technological achievements in fisheries [57,58,59]. Morocco developed a series of policies to promote its fisheries in the 1990s, including: opening the southern ports of Laayoune and Tan Tan and upgrading the infrastructure of the ports; adopting fiscal incentives to encourage Moroccan fishing vessels to unload at the country’s fishing ports in order to move away from the dependence of the domestic fisheries on the Spanish port of Las Palmas; and increasing the contribution of marine fisheries to the domestic economy and seeking more autonomy in the development and management of marine fisheries in the region [60,61,62].

Entering the 21st century, factors such as the overfishing of fishery resources, offshore fishing fleet, aging equipment of small fishing vessels, and international oil price shocks put the sustainable development of fisheries in North Africa under great pressure [62]. In order to protect fisheries’ resources, Mauritania has also established a closed season since 2002, with two months in spring and two months in autumn. The Moroccan government has given fisheries a prominent place in its latest economic development plan for 2011–2015 [60,61,62]. The Egyptian government is also increasing investment and R&D in science and technology to enhance the development of the fisheries industry [57,58,59,62]. The FiB index showed a steady upward trend from 2010 to 2019 owing to the increase in catches, reflecting both a sustainable spatial expansion and a positive increase in fishing effort [45], which indicate that the above-mentioned initiatives of North African countries to promote the sustainable development of marine fisheries have been effective and the marine fisheries in North Africa are now maintaining a good level of sustainable development.

4.2. East Africa

The East African region has many islands and coral reefs, which are a major impediment to deep-sea fishing. Therefore, fishing is limited to offshore or shallow bays, and catches are lower than the other four regions. Fishery resources in East Africa were gradually exploited in the 1950s and overfished from the 1960s to the 1980s, and marine ecosystems were destroyed. Thanks to the East African government’s focus on the sustainable development of marine fishery resources, from the 1990s to the first decade of the 21st century, fisheries were in a sustainable and rapid expansion. Currently, marine fisheries in East Africa are in an overfished state.

The main fish caught are Thunnus spp., Sepia officinalis, Sardina pilchardus and marine shellfish species, and the main marine fishing countries are Tanzania, Seychelles, Mozambique, and Madagascar. During 1950–1960, there was a slight increase in catch data, consisting mainly of mid-trophic and high-trophic level species, with a decrease in TLm and an increase in FiB indexes, which underlines the need for a more balanced exploitation of resources in East Africa [45]. From 1960 to 1990, changes in indicators during this period indicate the occurrence of the phenomenon of “fishing down food webs”. According to Pauly [33], this phenomenon, i.e., at lower trophic levels, leads first to increasing catches, then to a phase transition associated with stagnating or declining catches. These results indicate that present exploitation patterns are unsustainable. This may be due to the fact that increased fishing pressure and the use of destructive fishing gears and fishing techniques (e.g., beach seining, use of trawls, and rods and spears) have led to a significant reduction in the annual catches of fishery resources in the middle and upper trophic levels, and the destruction of marine ecosystems in East Africa, resulting in ecological degradation and degradation of fisheries’ productivity [63,64,65]. For instance, overfishing and dynamite bombing of fish, which have been going on for more than 40 years, have caused a serious decline in Tanzania’s fishery resources [66]. From 1990 to 2010, catches in East Africa have increased significantly, with an upward trend in TLm and FiB, indicating that the phenomenon of “fishing through food webs” has occurred [41], i.e., at higher trophic levels, which means that marine fisheries in East Africa are in a sustainable expansion [33,34]. This may be due to the initial effect of resource management under the control of the East African governments, with marine ecosystems being restored to some extent as a result. For example, in order to sustainably use marine fisheries resources, the Tanzanian government has strategically proposed a number of specific conservation measures in its fisheries policy announcement [67], such as the establishment of coastal reserves [68,69]. Kenya has also established a number of government-managed marine parks and reserves [39,68]. Madagascar launched the Fisheries Plan 2004–2007 [70].

From 2010 to the present, catches and ^3.25TLm showed an increasing trend, and TLm and FiB showed a decreasing trend, indicating that the current East African marine fisheries are in an overfished state. This may be due to limited fisheries’ surveillance and enforcement capacity in East Africa, which has led to illegal, unreported, and unregulated fishing and overfishing [70,71]. For instance, although laws in countries such as Kenya, Uganda, and Tanzania ban overfishing and unconventional fishing practices, such as the use of firearms, explosives, electrical shock devices, or poison substances for the purpose of fishing, organized criminal groups often use unconventional practices for fishing in East Africa, which has severe environmental impacts and seriously undermines the sustainable development of marine fisheries in the region [72]. In addition, the instability of political power in East Africa can affect policy making and overall governance in the fisheries sector, contributing to corrupt or illegal practices that are particularly detrimental to the sustainable management of fisheries resources [62,72,73].

4.3. Central Africa

Central Africa’s marine fishery resources have been exploited since the 1950s, overexploited in the 1960s, and began to recover from the 1970s to the beginning of the 21st century. In the first decade of the 21st century, low- and mid-trophic level species were overexploited, and marine fishery presented unsustainable exploitation patterns. Currently, the marine fishery resources in Central Africa are fully exploited and in a sustainable expansion phase.

The main marine fishing countries in Central Africa are Cameroon, the Republic of the Congo, and Gabon. Between 1950 and 1970, catches increased sharply. The TLm and ^3.25TLm indexes first decreased and then increased. Combined with the increasing trend in catch data and FiB index, it can be inferred that during this period, the rate of increase in catches was higher than the rate of decrease in trophic level, which implies that the fishing area was expanded, probably because the fisheries management was strengthened. The increase in TLm and ^3.25TLm and the decrease in catch data during 1970–1980 indicate that fishery resources are gradually recovering, probably due to the positive effect of fisheries management in Central African countries. Catches and FiB showed a slow upward trend during 1990–2010, and TLm and ^3.25TLm first showed a downward and then an upward trend, most probably reflecting technological advance, the development of fishing equipment, and a full exploitation of high-trophic level fishery resources [62]. The FiB index exhibited an upward trend since 2010 owing to the increase in catches, TLm, and ^3.25TLm indexes, indicating that the phenomenon of “fishing through food webs” was occurring [41], which suggests that the fishery was expanding to stocks only lightly exploited [56].

4.4. West Africa

Western Africa is adjacent to the Eastern Central Atlantic fishing area, from Gibraltar to the mouth of the Congo River, covering a total area of 14.2 million square kilometers [74,75,76]. Marine fishing is one of the main economic activities of West African countries. Except for the 1960s–1980s and the first decade of the 21st century, marine fisheries in West Africa have been mostly unsustainable.

The main fishery-producing countries in West Africa are Senegal, Mauritania, Nigeria, Ghana, and Guinea, with diverse types of fisheries and catches of small pelagic fish [4,16]. The catch data and FiB increased, while the observed TLm and ^3.25TLm decreased during 1950–1960, suggesting that as fishing areas in West Africa expanded, high-trophic level species were being overfished. From 1960 to 1980, the observed catches, TLm, ^3.25TLm, and FiB all maintained an increasing trend, which indicates that the phenomenon of “fishing through food webs” occurred while the annual catches of high-trophic level resources kept increasing steadily [41], which means that marine fisheries in West Africa were in a sustainable state during this period [33,34]. Over the period 1980–2000, the annual catches of high-trophic level species decreased continuously, while the annual catches of low- and mid-trophic level species increased. The marked decrease in the observed TLm and slow increase in FiB unambiguously indicate that the fishery resources were overexploited, reflecting an unsustainable spatial expansion during this period [45]. Overfishing, overcapacity, environmental change, habitat degradation, and unequal fishing agreements are the main influencing factors for the decline in catches in West Africa [77,78,79]. For instance, the catch of pelagic fishes from major landing sites along the Guinea Current Large Marine Ecosystem and Canary Current Large Marine Ecosystem in West Africa have shown fluctuations in abundance, which are thought to be linked to changes in environment [5].

During 2000–2010, the damaged fishery resources have partially recovered under the management of West African countries. Our study concluded that the development of fisheries in West Africa now presents sustainable exploitation patterns. This may be attributed to the fisheries agreements signed between West Africa and China and the EU. Most countries in West Africa lack well-developed fisheries management systems, have low capacity to assess reserves and fishing levels, and have problems in many aspects of human, institutional, and financial capacity [16,62,76]. However, the Fishery Access Agreements between West Africa and China and the EU, which represents an outsourcing of fishing in exchange for development aid or currency, has to some extent enhanced the fisheries management capacity in West Africa and contributed to the sustainable development of fisheries in this region [80,81,82]. Since 2010, West African fisheries have been overexploited. This may be attributed to the absence of effective management policies, the increase in the artisanal fishing sector, local purse seiners, foreign industrial fishing vessels operating within the framework of the bilateral agreements, and often illegal, unreported, unregulated (IUU) fishing fleets [4,5,6,7,12,17]. For example, in Senegal, the lack of employment opportunities, increasing demand for fish, and an absence of effective management policies have led to an increase in the artisanal fishing sector [16]. Incentive policies have encouraged the general move to motorized boats of the Senegalese artisanal fleet. This situation has facilitated the local adaptation of larger fishing gear, such as purse seine and gillnets [5,16]. Motorization has considerably expanded the area for artisanal fishing, simultaneously reducing travel time and extending fishing time, leading to an unprecedented increase in fish landings [5]. This increase, without effective management policies, has led to the overexploitation of marine fisheries since 2010, mainly by the artisanal fishing sector [5,12,16].

4.5. Southern Africa

Southern Africa has abundant marine fishery resources and superior marine fishing conditions, and fisheries play an important role in the national economy. These resources provide food security and contribute to the livelihoods of at least 30,000 coastal fishers along South Africa’s 3000-km coastline [83,84,85]. During the 1950s–1960s, the expansion of fishing areas accelerated. From the 1970s to the 1980s, fisheries’ development contracted, while from the 1980s to the 1990s, the fishery resources were first overexploited and then recovered to some extent. Since the 21st century, the fishing area has expanded, but the long-term overexploitation has caused some damage to the marine ecosystem of Southern Africa, which is not conducive to the long-term sustainable development of marine fisheries in this region. Currently, the region is in a state of overfishing. The main fishery-producing countries are Namibia, the Republic of South Africa, and Angola, all of which have high fish productivity due to the Benguela upwelling, and the main catches are Sardina pilchardus and Eleginus gracilis [85]. Catches and FiB were on an upward trend over the period 1950–1960, reflecting that the Southern African fishing area was in a sustainable and accelerated expansion during this period. This may be due to technological advances, and the development of mechanized fishing vessels, man-made fiber fishing gear and refrigeration equipment, which have led to a marked increase in catches and the gradual exploitation of fishery resources [45,62].

From 1970 to 1980, catches decreased sharply, while the annual catches of high-trophic level species increased significantly. Meanwhile, the increase in TLm and decrease in FiB indicate a deceleration of the fishery development [45], probably mainly due to the increasingly strict management of high seas fisheries, which restricted the fishing of fishery resources. Over 1980–1990, the catches, FiB, and TLm showed an overall upward trend, and the annual catches of high-trophic level species increased significantly, suggesting that the marine fishery recovered to some extent from the overexploited state in this period [41,45,56]. This may be mainly influenced by the post-independence fisheries policy of Namibia, a major fishing country in Southern Africa. Before 1990, fishing fleets from Europe and Asia fished in Namibia on a large scale and without restrictions, leaving most of Namibia’s fish stocks in a precarious state. After Namibia’s independence, its government established and implemented a resource management system to reduce fishing, which led to the recovery of marine fishery resources [62,85,86].

Over the period 1990–2000, the increase in all indicators reflects the phenomenon of “fishing through food webs” [41]. Since 2000, the decreasing trend in catches and FiB with the increasing trend in high-trophic level species and TLm indicate that the fishery resources are overexploited [33,34]. This means that most of the economic fish in the region are still fully fished or overfished [3], which is usually a consequence of long-term overfishing [86,87,88,89,90].

5. Conclusions and Policy Implications

5.1. Main Conclusions

Firstly, the development level of marine fisheries in Africa is very low; most countries are mainly traditional fisheries and cannot fully exploit the fishery resources in the surrounding waters, resulting in the plundering of the fishery resources in this region by the developed countries.

Secondly, the marine fishery resources of African countries have great variability. Broadly speaking, West, Central, and Southern African countries have more abundant marine fishery resources with a wide variety of fish. Countries in East and North Africa have fewer marine fishery resources. The exploitation of marine fishery resources in African coastal countries has broadly passed through the stages of under-exploitation, rapid exploitation, and over-exploitation. In the 1950s, African marine fisheries as a whole were in a state of gradual exploitation. Most of the fishing countries entered the rapid exploitation stage in the 1960s and 1970s. The fisheries’ resources in North, East, and West Africa were overexploited from the 1980s to 1990s, the level of marine biodiversity decreased, and the structural function of the marine ecosystem was gradually destroyed. The fishing areas in Central Africa were in a sustainable state with accelerated expansion. The fishery resources in Southern Africa were first overexploited and then restored to some extent. The accelerated expansion of fishing areas in the first decade of the 21st century has led to an unsustainable fishing-down process in East, Central, and Southern Africa, which has affected the community structure of the commercially exploited species in the three regions. Many economically important demersal fish species were overexploited, and major stocks of low-trophic-level species were fully exploited or overexploited. Marine fisheries in North and West Africa presented sustainable exploitation patterns. Currently, marine fisheries in all African regions are overfished, except for North and Central Africa, which are sustainably exploited.

5.2. Policy Implications, Study Limitations, and Future Research

Although marine fisheries in North Africa, West Africa, and Central Africa currently present sustainable exploitation patterns, the current state of marine fisheries’ development in Africa is still relatively backward, and the overall fisheries’ development level is low compared with other large marine areas in the world. In addition, any state is a phase, so based on the history and current development of marine fisheries in Africa, it is still necessary to pay attention to the overexploitation of marine fisheries and the deficiencies in fisheries management, which can provide a reference for the long-term sustainable and high-quality development of marine fisheries in Africa.

(1)

The policy implications of this analysis include the need to strengthen monitoring and management, and to promote international cooperation. African countries could establish naval and coast guard forces capable of maintaining maritime security, invest in the training of law enforcement officers, and establish relevant investigative procedures and institutions. In addition, relevant agreements and policy regulations could be developed in line with their fisheries policies and international treaties to make joint action against IUU fishing financially and legally viable, and applicable in national, regional, and international waters [62,91]. On the basis of existing international organizations, special working groups can be set up for different regions to step up the fight against illegal fishing activities.

(2)

The real-time monitoring and surveillance mechanisms for marine fishery resources covering the whole of Africa should be established as soon as possible, which are important for sustainable management of fisheries [92]. Similar mechanisms have been established in countries such as Kenya [92], the UK [93], and Australia [94], which help to dynamically keep track of the real-time changes in fish community structure under fishing activities, and accordingly develop effective measures and management strategies in order to adjust the number of different economic fish caught in a timely manner and implement fishing quota management. This not only ensures the transparency of fisheries’ management and decision making, but also promotes the recuperation and sustainable development of fish stocks while safeguarding the basic interests of fishermen [95,96].

(3)

African coastal countries should improve the current incomplete fisheries protection and management regulations, and make corresponding provisions on their fisheries’ management authority, foreign fishing activities in their waters, national fisheries management plans, and other relevant aspects to improve the effectiveness of the current laws [82]. Of particular importance is the improvement of vessel licensing systems. Implementing an effective licensing system for domestic or international vessels is an effective measure to control fisheries fishing and can reduce the amount of underreported and misreported fishery catches to a certain extent, thus achieving the goal of reducing illegal fishing [97,98,99]. In addition, closed season and closed areas should be established, fishermen registration and fishing vessel registration should be implemented, fishing intensity should be controlled, and fishing gear types and specifications should be restricted, etc. Meanwhile, law enforcement should be strengthened and measures such as fines and confiscation of fishing and transportation equipment should be taken against violators.

Since the problems of marine fisheries’ development in African coastal countries are universally applicable, this paper does not only focus on East, West, and Southern Africa, but has relevant implications at the policy level for the sustainable development of marine fisheries in Africa as a whole.

There are some shortcomings in this study that should be considered when interpreting the results. Fishery catches can change due to a range of different factors, such as changes in fishery fleets/markets or management regulations, as well as naturally occurring environmental shifts in productivity. In addition, since the marine fishing industry is driven by profits, the TLm index could be sensitive not only to fishery-induced changes at the ecosystem level, but also to long-term environmental variation and economic, technological, and cultural factors. Future studies should try to adopt spatial panel regression models, such as the spatial panel Durbin model (SPDM) and spatio-temporal geographically weighted regression (GTWR), to further quantify these factors and discuss their effects. In the future, we will focus on the driving mechanisms of the stage-specific socio-economic indicators on marine ecosystems based on the availability of data.