Relationship between pelagic larval duration and abundance of tropical fishes on temperate coasts of Japan

The influence of pelagic larval duration (PLD) and egg type dispersal capabilities of 35 demersal and pelagic-spawning tropical fish species is examined in relation to their abundance on the temperate coasts of Japan. The PLDs of pelagic spawners were significantly longer than those of demersal spawners, and a high occurrence of pelagic spawners on the temperate coasts suggests that these fishes are more easily transported to temperate coasts than demersal spawners. For demersal spawners, the common species on the temperate coasts had significantly longer PLDs than the rare species; this suggests that PLD is a major factor influencing the distribution patterns of tropical demersal spawners on temperate coasts. Moreover, a negative correlation between PLD and the abundance of some species of pelagic and demersal spawners suggests the presence of reproductively active fishes in northern subtropical and even in temperate waters.     

SMART: A Spatially Explicit Bio-Economic Model for Assessing and Managing Demersal Fisheries,with an Application to Italian Trawlers in the Strait of Sicily

Management of catches, effort and exploitation pattern are considered the most effective measures to control fishing mortality and ultimately ensure productivity and sustainability of fisheries. Despite the growing concerns about the spatial dimension of fisheries, the distribution of resources and fishing effort in space is seldom considered in assessment and management processes. Here we propose SMART (Spatial MAnagement of demersal Resources for Trawl fisheries), a tool for assessing bio-economic feedback in different management scenarios. SMART combines information from different tasks gathered within the European Data Collection Framework on fisheries and is composed of: 1) spatial models of fishing effort, environmental characteristics and distribution of demersal resources; 2) an Artificial Neural Network which captures the relationships among these aspects in a spatially explicit way and uses them to predict resources abundances; 3) a deterministic module which analyzes the size structure of catches and the associated revenues, according to different spatially-based management scenarios. SMART is applied to demersal fishery in the Strait of Sicily, one of the most productive fisheries of the Mediterranean Sea. Three of the main target species are used as proxies for the whole range exploited by trawlers. After training, SMART is used to evaluate different management scenarios, including spatial closures, using a simulation approach that mimics the recent exploitation patterns. Results evidence good model performance, with a noteworthy coherence and reliability of outputs for the different components. Among others, the main finding is that a partial improvement in resource conditions can be achieved by means of nursery closures, even if the overall fishing effort in the area remains stable. Accordingly, a series of strategically designed areas of trawling closures could significantly improve the resource conditions of demersal fisheries in the Strait of Sicily, also supporting sustainable economic returns for fishermen if not applied simultaneously for different species.     

The Seascape of Demersal Fish Nursery Areas in the North Mediterranean Sea,a First Step Towards the Implementation of Spatial Planning for Trawl Fisheries

The identification of nursery grounds and other essential fish habitats of exploited stocks is a key requirement for the development of spatial conservation planning aimed at reducing the adverse impact of fishing on the exploited populations and ecosystems. The reduction in juvenile mortality is particularly relevant in the Mediterranean and is considered as one of the main prerequisites for the future sustainability of trawl fisheries. The distribution of nursery areas of 11 important commercial species of demersal fish and shellfish was analysed in the European Union Mediterranean waters using time series of bottom trawl survey data with the aim of identifying the most persistent recruitment areas. A high interspecific spatial overlap between nursery areas was mainly found along the shelf break of many different sectors of the Northern Mediterranean indicating a high potential for the implementation of conservation measures. Overlap of the nursery grounds with existing spatial fisheries management measures and trawl fisheries restricted areas was also investigated. Spatial analyses revealed considerable variation depending on species and associated habitat/depth preferences with increased protection seen in coastal nurseries and minimal protection seen for deeper nurseries (e.g. Parapenaeus longirostris 6%). This is partly attributed to existing environmental policy instruments (e.g. Habitats Directive and Mediterranean Regulation EC 1967/2006) aiming at minimising impacts on coastal priority habitats such as seagrass, coralligenous and maerl beds. The new knowledge on the distribution and persistence of demersal nurseries provided in this study can support the application of spatial conservation measures, such as the designation of no-take Marine Protected Areas in EU Mediterranean waters and their inclusion in a conservation network. The establishment of no-take zones will be consistent with the objectives of the Common Fisheries Policy applying the ecosystem approach to fisheries management and with the requirements of the Marine Strategy Framework Directive to maintain or achieve seafloor integrity and good environmental status.     

Winter aspects of the ichthyoplankton community in Antarctic Peninsula waters

Summary Ichthyoplankton was sampled from the Antarctic Peninsula area of the South Polar Ocean in early winter (May and June 1986). A total of 153 eggs from two species and 1368 larvae or juvenile stages from 12 species were obtained. These included pelagic species, and demersal species with a long pelagic larval or juvenile phase. Most abundant were larvae of Pleuragramma antarcticum and Notothenia kempi, and eggs of Notothenia neglecta. The distribution of notothenioid and paralepidid larvae was apparently unaffected by ice cover, whereas myctophid larvae were confined to ice-free waters. Areas where newly hatched Chionodraco hamatus occurred coincided with dense aggregations of Euphausia superba (Krill) furcilia larvae which is a potential food resource during winter. The hatching of icefish larvae during winter is apparently independent of the seasonal production cycle. Epipelagic eggs of Notothenia neglecta were found during the spawning season, which suggests that eggs ascend to the surface after demersal spawning and that development takes place near the sea surface during winter. Larvae of Notothenia kempi were chiefly confined to shelf and slope waters to the west of the Antarctic Peninsula, with larger larvae found in coastal shelf areas. Pleuragramma antarcticum occurred in the coastal waters off the Biscoe Islands, in the Gerlache Strait, and in the northern Bransfield Strait. The smallest larvae were found in the northern Bransfield Strait, whereas those at the Biscoe Islands and in Gerlache Strait waters were larger and of a similar size. A cyclonic gyre to the west of the Antarctic Peninsula observed in the austral summer was likely to have affected the larval drift of Pleuragramma antarcticum and Notothenia kempi. Differences in the timing of spawning and hatching and the vertical distribution of these larvae will lead to different transport and spatial distribution patterns. It is hypothesized that early winter conditions do not imply severe limitations on the year-class success of larval fish. Dispersal and increased mortality may occur during the second half of the winter.     

Carbon and nitrogen stable isotopic inventory of the most abundant demersal fish captured by benthic gears in southwestern Iceland (North Atlantic)

Stable isotopes (δ¹³C and δ¹⁵N) were used to examine the origin of organic matter for the most representative demersal species of the SW Icelandic fishery, accounting for over 70% of landings of those species in the North Atlantic. Samples were collected during a 2-week period in early September 2004 from landings and directly during fishing cruises. Stable isotopes showed that particulate organic matter and sedimentary organic matter were at the base of the food web and appeared to fill two different compartments: the pelagic and the benthic. The pelagic realm was composed of only capelin and sandeel; krill and redfish occupied an intermediate position between pelagic and benthic realms; while anglerfish, haddock, cod and ling resulted as the true demersal species while tusk, rays and plaice were strongly linked to the benthic habitat.     

In Retrospect the Assumption of Sustainability for Atlantic Fisheries has Proved an Illusion

Fishery landings data series from 1970 to 2002 for the Northeast (FAO Area 27) and Northwest Atlantic (Area 21) with 73 and 42 species or species groups respectively, were mapped onto single charts as a diagnostic of the overall state of fisheries in these two regions, and could be appreciated simultaneously for the entire exploited suite of species as a series of contiguous bar charts. Charts were compared with that for a similar data set of 42 species or species groups from the Mediterranean and Black Seas (FAO Area 37). A “traffic light convention” partitioned the range of landings by species over the period into four equal intervals; coloured respectively red, yellow, green and blue between zero and the highest annual landing of the species. This allowed a model-free display of changes in the timing of species’ landings at the overall ecosystem level, as represented by the important commercial resources in the three areas. The year T₅₀ by which 50% of species landings had been harvested over the period, was considered a comparable measure of the response of individual species to exploitation. For a significant proportion of groundfish and pelagic fishes, the time to reach T₅₀ occurred early in the Atlantic time series. The hypothesis was tested that this measure of the depletion schedule is related to some aspect of species biology, as judged by data from the FISHBASE database. Except for commercial invertebrates where landings peaked late in the Northwest Atlantic time series, no significant regression was found between T₅₀ values per species and any biological characteristic of the species of finfish tested, suggesting that scheduling may reflect overcapacity and targeting by fisheries and/or regime changes. A decline in peak landings proceeded sequentially over time for the large proportion of all finfish species in the North Atlantic following a broadly similar trajectory. Possible exceptions were deeper water species where fisheries began later, suggesting that “fishing down the bathymetry” has occurred. A more synchronous “pulse” of high landings occurred in the Mediterranean and Black Seas in the mid-late 1980s, which was postulated as due to an increase in system productivity. Although regime changes and quota management cannot be excluded as partly responsible for the persistent low landings late in many time series, the main conclusion is that for all three areas, the effects of fishing overshadow those resulting from differing biological characteristics, habit, or species interactions. Although quota control may in part be responsible for low landings of some species late in the time series, the fishery management regimes that applied during 1970–2002 cannot be considered sustainable. This was confirmed by comparative analysis fitting a variety of models to the raw landing data. Of the mathematical models considered, the Hubbert curve, first used to predict the trajectory of extraction of non-renewable petroleum resources globally over time, best fitted the largest proportion of species time series. This seems to confirm that a hypothesis of harvest sustainability cannot be supported by the landing data.     

Gargoor trap fishery in Kuwait,catch rate and species composition

Kuwait's fisheries include shrimp trawlers, gill nets, intertidal stake nets, and demersal fish traps, known locally as gargoor. The gargoor fishery used to be the nation's most important in terms of value and landings volume, but declines in catch rates have reduced its ranking. This paper describes the status of the gargoor artisanal fishery. The main landings place was sampled for catch and effort, and fish length‐frequency data from May 2003 to December 2005. The catch rate, monthly average number of boats operating, and the number of gargoor cleared were estimated for dhow boats fishing in Kuwait's waters and international waters, and speed boats operating in Kuwait waters only. Over the duration of the study period, the speedboat catch rates were higher than those of dhow boats, i.e., 3.7 kg/trap‐pull vs. 2.6 and 2.5 kg/trap‐pull for dhows fishing in Kuwait's territorial waters and international waters, respectively. The grouper, Epinephelus coicodes, was the main species captured, contributing 19.3% and 17.8% to the dhow catch in Kuwait waters and international waters, respectively. The catch rates by dhow boats declined from an average of 4.7 kg/trap‐pull in 2003 to 2.7 kg/trap‐pull in 2005 representing a 41% decrease. If this decreasing catch rate trend continues, then fishing effort should be reduced to allow stock recovery. It is recommended that the number of gargoor fished in Kuwaiti waters should be limited and that several no‐fishing zones be established to ensure the minimum spawning stock biomass and preserve biodiversity for all fisheries.     

Parasites as biological tags in population studies of demersal and pelagic fish species

Among the different techniques applied in a holistic approach for fish stock identification, the use of parasites as "biological tags" is becoming increasingly important. In this presentation, our recent studies on the use of some parasite species, identified by genetic markers, and the parasite/fauna composition, in stock identification of demersal (Merluccius merluccius), small pelagic (Trachurus trachurus), and large pelagic fish species (Xiphias gladius) are reviewed. Different species of Anisakis and Hysterothylacium were genetically identified by the application of genetic (allozyme) markers. Statistically significant differences in the spatial distribution of distinct species of Anisakis were found in the fish considered. As to the species of Hysterothylacium genetically detected, different relative proportions were detected in several Mediterranean and Atlantic samples of swordfish (X. gladius). This study demonstrates the potential value of these anisakid nematodes, at both larval and adult stages, as "biological tags" for these fish species in European waters.     

Effects of fishing and acidification‐related benthic mortality on the southeast Australian marine ecosystem

Oceanic uptake of anthropogenic carbon dioxide (CO₂) is altering the carbonate chemistry of seawater, with potentially negative consequences for many calcifying marine organisms. At the same time, increasing fisheries exploitation is impacting on marine ecosystems. Here, using increased benthic‐invertebrate mortality as a proxy for effects of ocean acidification, the potential impact of the two stressors of fishing and acidification on the southeast Australian marine ecosystem to year 2050 was explored. The individual and interaction effects of the two stressors on biomass and diversity were examined for the entire ecosystem and for regional assemblages. For 61 functional groups or species, the cumulative effects of moderate ocean acidification and fishing were additive (30%), synergistic (33%), and antagonistic (37%). Strong ocean acidification resulted in additive (22%), synergistic (40%), and antagonistic (38%) effects. The greatest impact was on the demersal food web, with fishing impacting predation and acidification affecting benthic production. Areas that have been subject to intensive fishing were the most susceptible to acidification effect, although fishing also mitigated some of the decline in biodiversity observed with moderate acidification. The model suggested that ocean acidification and long‐term fisheries exploitation could act synergistically with the increasing sensitivity to change from long‐term (decades) fisheries exploitation potentially causing unexpected restructuring of the pelagic and demersal food webs. Major regime shifts occur around year 2040. Greater focus is needed on how differential fisheries exploitation of marine resources may exacerbate or accelerate effects of environmental changes such as ocean acidification.     

Management strategies for sustainable invertebrate fisheries in coastal ecosystems of Galicia (NW Spain)

Artisanal coastal invertebrate fisheries in Galicia are socio-economically important and ecologically relevant. Their management, however, has been based on models of fish population dynamics appropriate for highly mobile demersal or pelagic resources and for industrial fisheries. These management systems focus on regulating fishing effort, but in coastal ecosystems activities that change or destruct key habitats may have a greater effect on population abundance than does fishing mortality. The Golfo Artabro was analysed as a representative example of a coastal ecosystem in Galicia, and the spider crab Maja squinado used as a model of an exploited coastal invertebrate, for which shallow coastal areas are key habitats for juvenile stages. The commercial legal gillnet fishery for the spider crab harvests adults during their reproductive migrations to deep waters and in their wintering habitats. Illegal fisheries operate in shallow waters. The annual rate of exploitation is >90%, and <10% of the primiparous females reproduce effectively at least once. A simple spatially-explicit cohort model was constructed to simulate the population dynamics of spider crab females. Yield- and egg-per-recruit analyses corresponding to different exploitation regimes were performed to compare management policies directed to control the fishing effort or to protect key habitats. It was found that the protection of juvenile habitats could allow increases in yield and reproductive effort higher than in the present system, with such protection based in the control of the fishing effort of the legal fishery. Additionally, there is an urgent need for alternative research and management strategies in artisanal coastal fisheries based on the implementation of a system of territorial use rights for fishers, the integration of the fishers into assessment and management processes, and the protection of key habitats (marine reserves) as a basic tool for the regulation of the fisheries.     

Ontogeny of behaviour in larvae of marine demersal fishes

The development of behaviours that are relevant to larval dispersal of marine, demersal fishes is poorly understood. This review focuses on recent work that attempts to quantify the development of swimming, orientation, vertical distribution and sensory abilities. These behaviours are developed enough to influence dispersal outcomes during most of the pelagic larval stage. Larvae swim in the ocean at speeds similar to the currents found in many locations and at 3–15 body lengths per second (BL s⁻¹), although, based on laboratory measurements, species from cold environments swim slower than those from warm environments. At least in warm-water species, larvae swim in an inertial hydrodynamic environment for most of their pelagic period. Unfed swimming endurance is >10 km from about 8–10 mm, and reaches more than 50 km before settlement in several species. Larval fishes are efficient swimmers. In most species, a large majority of larvae have orientated swimming in the ocean, but the precision of orientation does not improve with growth. Swimming direction of the larvae frequently changes ontogenetically. Vertical distribution changes ontogenetically in most species, and both ontogenetic ascents and descents are found. Development of schooling is poorly understood, but it may influence speed, orientation and vertical distribution. Sensory abilities (hearing, olfaction, vision) form early, are well developed and are able to detect cues relevant to orientation for most of the pelagic larval stage. All this indicates that the passive portion of the pelagic larval duration will be short, at least in most warm-water species, and that behaviour must be taken into account when considering dispersal, and in particular in dispersal models. Although quantitative information on the ontogeny of some behaviours is available for a relatively small number of species, more research in this field is required, especially on species from colder waters.     

The United Kingdom’s role in North Sea demersal fisheries: a hundred year perspective

This study compiles 100?years of North Sea demersal landings, focusing on the UK, and relating them to historical events and political, technological and economical drivers that influenced demersal fisheries. In the early twentieth century, aided by technological advances, the UK, and in particular England, had unchallenged dominance in North Sea demersal fisheries. Since then, the two World Wars and other political developments have had a great impact on British fisheries. Between the 1920s and 1960s, English ports shifted their interests away from the North Sea towards highly profitable distant waters, whereas the Scottish fleet relied less on these fishing grounds. Meanwhile, especially in the 1960s, other European countries expanded their fisheries, undermining Britain??s lead. In the 1970s and 1980s, Scotland benefitted from mainly fishing in the North Sea. Firstly, the assertion of 200 nautical miles Exclusive Economic Zones made the distant waters inaccessible to English fleets at a time when England??s fisheries were highly dependent on them. Secondly, the relatively minor activity in the North Sea by the English compared to the Scottish fleets coincided with the establishment of the Common Fisheries Policy. This had implications when total allowable catches were first implemented because quota allocations to countries were based on their recent catches from the North Sea. Thus, after the loss of fishing opportunities in distant waters, the North Sea once more became an important fishing ground for Britain, just as in the early twentieth century, however, the emphasis of fisheries had shifted from England to Scotland.     

Molecular phylogeny of the three paedomorphic Mediterranean gobies (Perciformes: Gobiidae)

Pelagic gobies are considered of particular zoological interest because the acquisition of a pelagic lifestyle is achieved through the persistence of larval anatomical features. The Mediterranean Sea is inhabited by three goby species (Aphia minuta, Crystallogobius linearis and Pseudaphya ferreri) characterized by paedomorphic traits. Owing to the shared larval morphological features, these species have generally been considered as a monophyletic group. This study aimed at establishing the phylogenetic relationships of these paedomorphic species within the family Gobiidae to ascertain whether the pelagic lifestyle achieved through paedomorphosis is due to an event that took place in a common ancestor or not. For this purpose, we amplified by polymerase chain reaction and sequenced the mitochondrial 12S rDNA (complete sequence) and 16S rDNA (partial sequence) of 15 Mediterranean gobies. The phylogenetic analysis strongly supported the polyphyletic origin of the three paedomorphic gobies, indicating that the heterochronic change leading to the retention of larval features seems to have occurred independently in the ancestors of these species. Thus, the sharing of morphological traits can be considered homoplasious and the classification of these species in the same taxonomic group is rejected on the basis of molecular data.     

Angel sharks (Squatinidae): A review of biological knowledge and exploitation

Angel sharks (Squatina spp.) are distributed in warm temperate to tropical waters around the world. Many species occur in shelf seas and exhibit seasonal inshore–offshore migrations, moving inshore to give birth. Consequently, there can be high spatial overlap of angel shark populations with fisheries and other human activities. Their dorso-ventrally flattened body shape, large size (most species attain >100 cm total length, L_T) and demersal nature means that they may be taken in a variety of demersal fishing gears from birth. Available data indicate that angel sharks typically have a biennial reproductive cycle, with litter sizes generally <20 and the young born at c. 20–30 cm. The biological characteristics of angel sharks render them susceptible to overexploitation, as exemplified by the decline of Squatina squatina from many parts of its former range in the north-east Atlantic and Mediterranean Sea. Currently, half of the 22 recognized extant species of angel shark are classed as Threatened on the International Union for Conservation of Nature (IUCN) Red List (with a further three classified as Data Deficient). Given the biological vulnerability of angel sharks, and that many species are data-limited, the current paper provides a review of available biological information and fisheries data pertaining to this family.     

Spatial management of the Mediterranean bottom-trawl fisheries: the case of the southern Aegean Sea

A time series of survey abundance indices for commercially important demersal fish and cephalopod species, inhabiting the narrow continental shelf of the southern Aegean Sea, is analyzed in relation to the topography of the area in order to evaluate the impact of different spatial fishery bans on the bottom-trawl fishery. With reference to the current situation, results suggested that implementation of the 1967/2006 EC Regulation, which bans bottom-trawl activities within 1.5 NM off the coast, will significantly increase (20–80%, depending on the species) the proportion of the populations that are inaccessible to the bottom-trawl fishery. It might also result in shifting of fishing activities toward deeper waters, adding fishing pressure onto slope resources inhabiting the slope. As depth determines, to a large extent, the distribution pattern of the species, it constitutes a variable of crucial importance for the spatial management of marine fisheries and should be taken into account when adopting relevant management regimes.     

Population structure in the pan-oceanic wreckfish, Polyprion americanus (Teleostei: Polyprionidae), as indicated by mtDNA variation

The wreckfish Polyprion americanus , a large [>1 m total length ( L _T)] demersal teleost, is distributed globally in temperate waters, including both sides of the North and South Atlantic Oceans, the Mediterranean, the western South Pacific, and the southern Indian Ocean. Wreckfish spawn off the south-eastern U.S. on an area of the Blake Plateau (the Charleston Bump) characterized by an extensive ridge having approximately 100 m relief, in 450–600 m depths. Juvenile wreckfish (<60 cm L _T) are pelagic and, in the North Atlantic, are not reported from the Blake Plateau fishing area, but occur in by-catch and fishery landings in the eastern Atlantic. Analysis of nine restriction fragment length profiles from a PCR-amplified fragment (∼1.5 kb) of the ND1 mitochondrial gene indicated no stock separation between eastern North Atlantic (Azores, Majorca, Madeira), and western North Atlantic (Blake Plateau) wreckfish. Restriction site differences separate western South Atlantic wreckfish from the North Atlantic; however, South Atlantic wreckfish share restriction-site similarities with western Pacific wreckfish that are not shared with North Atlantic wreckfish. North Atlantic circulation provides a mechanism for a long-lived pelagic stage to be dispersed from Blake Plateau spawning grounds to the eastern North Atlantic. Global circulation patterns may explain both the dispersal of mtDNA haplotypes and the disjunct distribution of wreckfish body lengths in a temperate, deep-water vagile species with an extended pelagic juvenile stage such as wreckfish.     

Spawning vocalizations in male freshwater gobiids (Pisces,Gobiidae)

Synopsis Males of two freshwater Italian gobies, the common goby, Padogobius martensii and the panzarolo goby, Knipowitschia punctatissima, emit trains of low-frequency pulses, i.e. drumming sounds, in the presence of a ripe female in the nest. In P, martensii the drumming sound is usually followed by a tonal sound (complex sound). Examination of the pulse structure suggests that these sounds are produced by muscles acting on the swimbladder. Both species exhibited high emission rates of spawning sounds, especially before the beginning of oviposition. Moreover, spawning sound production ceased only after the female abandoned the nest, which always occurred at the end of oviposition. This is the first study reporting the production among fishes of distinct sounds during protracted spawning. Unlike sounds produced just before mating by fishes with planktonic or demersal zygotes, the spawning sound production of these gobies does not function to coordinate mating events in the nest. The presence of a two-part vocalization by male P. martensii even suggests a functional dichotomy of spawning sounds in this species.     

Remarkable ophidiid larva (Neobythitinae) from New Guinean waters

A new type of ophidiid larva referred to the Neobythitinae is described on the basis of one specimen (22.5 mm in standard length: SL) found in the “Dana” flatfish larval collection from New Guinean waters. It is characterized by a very high body (ca. 48% SL), with a single elongate first dorsal-fin ray and protruding abdominal cavity with a long fleshy appendage at its posteroventral end. Generic and specific affinities of the larva are discussed. It is supposed that the larva belongs to one of the Pycnocraspedum species, probably to P. squamipinne.     

Distribution of Anisakis larvae, identified by genetic markers, and their use for stock characterization of demersal and pelagic fish from European waters: an update

In the present paper, recent results obtained on the use of different distributions observed in larval species of Anisakis, genetically identified by means of allozyme markers, for stock characterization of demersal (Merluccius merluccius), small (Trachurus trachurus) and large pelagic (Xiphias gladius) finfish species in European waters, are reviewed and discussed. Several species of Anisakis were identified in the three fish hosts: A. simplex (s.s.), A. physeteris, A. typica, A. ziphidarum, A. pegreffii, A. brevispiculata and A. paggiae. Canonical discriminant analysis performed on all the samples of the three fish species collected in areas comprising their geographical range, according to the different species of Anisakis identified, showed distinct fish populations in European waters. In all the three fish hosts, the pattern of distribution of Anisakis larvae allowed discrimination of Mediterranean stocks from Atlantic stocks. In the case of swordfish, the possible existence of a southern Atlantic stock separated from a northern one is also suggested. Congruence and discordance with the population genetic data inferred from allozyme markers on the same samples of the three fish species are also discussed.     

The key role of the Northern Mozambique Channel for Indian Ocean tropical tuna fisheries

The Northern Mozambique Channel (NMC) is a tropical area of ~?1 million km² where pelagic fisheries supply proteins to more than 9 million people living in Comoros, Mayotte, and along the coasts of Mozambique, Tanzania and Madagascar. Although uncertain, statistics suggest that about 20,000 mt of tropical tuna and other pelagic fish are annually caught by artisanal fisheries in the area. The NMC is also a major seasonal fishing ground for high-seas fleets that export an annual average catch of more than 20,000 mt to tuna can and sashimi markets of high-income countries for a value estimated to be more than 100 million USD. The fisheries productivity of the NMC appears to be highly variable in relation to strong annual and seasonal variability in oceanographic conditions. Our review shows that the NMC is a key feeding area for tropical tunas and a major spawning area for skipjack tuna thanks to warm waters and strong mesoscale activity that results in the enrichment of surface waters and efficient energy transfers enabled by short food chains. Projections of climate models under future warming scenarios predict some strong changes in the oceanographic conditions of the NMC which has already experienced substantial warming over the last decades. Changes in the pelagic ecosystem of the NMC could have dramatic consequences on the coastal populations that are expected to increase towards 100 million people by 2100. Improving monitoring systems and collecting information on the socio-economics of coastal fisheries is crucial to assess the dependence of NMC populations on tuna resources and empower the countries to more involvement in the management of tuna stocks.