The small pelagic fishery of the Pemba Channel, Tanzania: What we know and what we need to know for management under climate change

Sekadende, Baraka C.; Scott, Lucy; Anderson, J. G. C.; Aswani, Shankar; Francis, Julius; Jacobs, Zoe; Jebri, Fatma; Jiddawi, Narriman; Kamukuru, Albogast T.; Kelly, Stephen; Kizenga, Hellen; Kuguru, Baraka; Kyewalyanga, Margareth S.; Noyon, Margaux; Nyandwi, Ntahondi; Painter, Stuart C.; Palmer, Matthew R.; Raitsos, Dionysios Ε.; Roberts, Michael J.; Sailley, Sévrine F.; Samoilys, Melita; Sauer, W. H. H.; Shayo, Salome Daniel; Shaghude, Yohana; Taylor, Stephen K.; Wihsgott, Juliane U.; Popova, Ekaterina

doi:10.1016/j.ocecoaman.2020.105322

Cited by 50 publications

(31 citation statements)

References 67 publications

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“…Additionally, data recorders were known to lack capacity/knowledge to identify and group fish species in their respective categories, leading to inaccuracies in recording the catches of small pelagics (sardines and anchovies), for example [78,79]. This makes the available historical data uncertain and their use problematic [80,81].…”

Section: Discussionmentioning

confidence: 99%

“…Such ecosystem changes can lead to changes in fish composition and cause shifts in the distribution of certain species [15][16][17]. The most notable effects of El Niño on the fisheries, particularly the pelagic fishery, are changes in the latitudinal and vertical distribution of species, size structure, reproductive processes and an overall decline in landings [80]. These are expected to lead to an increase in fisher migration, a shift in the distribution of target species and associated loss of revenues, further affecting fishers' livelihoods and food security.…”

Section: Discussionmentioning

confidence: 99%

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A Major Ecosystem Shift in Coastal East African Waters During the 1997/98 Super El Niño as Detected Using Remote Sensing Data

et al. 2020

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Under the impact of natural and anthropogenic climate variability, upwelling systems are known to change their properties leading to associated regime shifts in marine ecosystems. These often impact commercial fisheries and societies dependent on them. In a region where in situ hydrographic and biological marine data are scarce, this study uses a combination of remote sensing and ocean modelling to show how a stable seasonal upwelling off the Kenyan coast shifted into the territorial waters of neighboring Tanzania under the influence of the unique 1997/98 El Niño and positive Indian Ocean Dipole event. The formation of an anticyclonic gyre adjacent to the Kenyan/Tanzanian coast led to a reorganization of the surface currents and caused the southward migration of the Somali–Zanzibar confluence zone and is attributed to anomalous wind stress curl over the central Indian Ocean. This caused the lowest observed chlorophyll-a over the North Kenya banks (Kenya), while it reached its historical maximum off Dar Es Salaam (Tanzanian waters). We demonstrate that this situation is specific to the 1997/98 El Niño when compared with other the super El-Niño events of 1972,73, 1982–83 and 2015–16. Despite the lack of available fishery data in the region, the local ecosystem changes that the shift of this upwelling may have caused are discussed based on the literature. The likely negative impacts on local fish stocks in Kenya, affecting fishers’ livelihoods and food security, and the temporary increase in pelagic fishery species’ productivity in Tanzania are highlighted. Finally, we discuss how satellite observations may assist fisheries management bodies to anticipate low productivity periods, and mitigate their potentially negative economic impacts.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

A Major Ecosystem Shift in Coastal East African Waters During the 1997/98 Super El Niño as Detected Using Remote Sensing Data

et al. 2020

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“…Many marine animals' planktonic phases have been directly supported by phytoplankton, the second most important food source for small pelagic fish after zooplankton (Bachiller andIrigoien 2015, Abdellaoui et al 2017). In Tanzania, phytoplankton and small pelagic fish abundances are mainly controlled by different predominant oceanic processes (Sekadende et al 2020a, which are influenced by two seasonal monsoon wind systems, the northeast (NE) monsoon which runs from November to March, and the southeast (SE) monsoon season from May to September (Mahongo and Shaghude 2014). Phytoplankton and small pelagic fish composition, abundance and distribution vary greatly between the two seasons (Kizenga 2020).…”

Section: Introductionmentioning

confidence: 99%

Seasonality in Phytoplankton Species Composition and their Influence on Small Pelagic Fish along the Western Pemba Channel

Kyewalyanga

2022

Tanz. J. Sci.

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The influence of phytoplankton biomass on small pelagic fish groups was studied at three sites along the Western Pemba Channel, to assess the contribution of seasonality. Sampling took place at the three sites in the coastal waters of Tanga, Tanzania. The study used in-situ data from July 2016 to January 2017, remotely-sensed chlorophyll-a data from August 2016 to August 2017 and 2019–2020, and small pelagic fish catch data from the same periods as the remotely-sensed data. The dominant groups at all the three sites were diatoms, dinoflagellates, and cyanobacteria, with diatoms having the highest number of species compared to the other two. In comparison to the southeast monsoon season, phytoplankton species and biomass were significantly higher during the northeast monsoon season. The most plentiful fish were anchovies, which had high peaks in both seasons, followed by sardinella, while mackerel had the lowest catch. Chlorophyll-a and anchovy catches showed a positive correlation; however, the relationship was not significant (r = 0.47, df = 11, p = 0.12). Both variables showed the highest peaks in October, while other fish groups showed very weak and insignificant positive or negative correlations. These findings suggest that factors other than phytoplankton biomass contribute to controlling small pelagic fish availability. Keywords: Phytoplankton; monsoon seasons; chlorophyll-a; Pemba Channel; small pelagic fish.

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“…Trap and seine net fisheries, for example, are frequently dominated by herbivorous fishes (e.g., [64][65][66]), which tend to respond to habitat and/or benthic processes [65,67,68]. However, given their intrinsically strong relationship with total fish productivity, planktivore sweet spots are likely to be disproportionally important for many reef-based fisheries [35][36][37][38]. Nevertheless, it is conceivable that seascapes that feature favourable conditions for both plankton subsidy and herbivore sweet spots will offer maximised yield opportunities for tropical reef fisheries.…”

Section: Plos Biologymentioning

confidence: 99%

“…While "optimal rewards" are context dependent [25,27], locations that concentrate target fish biomass production (Fig 1B ) will likely also support increased yields (or profit) relative to the rest of the seascape [26,28,30,31]. Plankton inputs, for example, tend to drive planktivorous and predatory fish aggregations in suitable habitats [11,22,23,32,33], with potential flow-on effects for important coastal and reef fisheries [34][35][36][37][38]. But how common are these "sweet spots" of fish concentration, both globally and locally, and what is the role of spatial subsidies in shaping their occurrence?…”

Section: Introductionmentioning

confidence: 99%

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The small pelagic fishery of the Pemba Channel, Tanzania: What we know and what we need to know for management under climate change

Cited by 50 publications

References 67 publications

A Major Ecosystem Shift in Coastal East African Waters During the 1997/98 Super El Niño as Detected Using Remote Sensing Data

A Major Ecosystem Shift in Coastal East African Waters During the 1997/98 Super El Niño as Detected Using Remote Sensing Data

Seasonality in Phytoplankton Species Composition and their Influence on Small Pelagic Fish along the Western Pemba Channel

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