Browsing by Author "Correia, Edna"
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- Coastal waters of a marine protected area of the Bijagós Archipelago, West Africa, shelter juvenile fishes of economic and ecological importancePublication . Correia, Edna; Granadeiro, J. P.; Regalla De Barros, Aissa; Catry, PauloIn many marine ecosystems small pelagic fish exert a crucial role in controlling the dynamics of the community, mainly due to their high biomass at intermediate levels of the food web. These fish use coastal marine ecosystems as nursery areas, but also to forage and to avoid predation or competition. We studied spatial, seasonal, lunar and diel variations in a coastal fish community from a marine protected area of the Bijagós Archipelago, Guinea-Bissau. Fish were sampled with 46 beach seine net sessions in 2015 and 2016. A total of 35 fish species of 25 families were captured. Fish abundance varied between years and seasons, with a higher abundance in the dry season, but not by lunar tide. Nonetheless, the community composition was broadly similar over the seasons, among islands and between lunar tides. Clupeidae, Haemulidae and Gerreidae were the most abundant fish families. Sardinella maderensis highly dominated the captures throughout the year, with catches much higher than any other species. The differences in abundance between seasons and years may be related with movements to or from the shore due to feeding activity or to avoid predation, or else to differences in recruitment between years. There were no significant diel differences in species richness and diversity, although higher numbers of fish were captured during daytime. For most species the majority of individuals captured were immature, highlighting the importance of the archipelago as nursery area for several species. These small pelagics, and particularly Sardinella maderensis, represent the main prey for several marine predators. Thus, the conservation of such fish species may be key for the management of the Bijagós Archipelago.
- Foraging behaviour and diet of Brown boobies Sula leucogaster from Tinhosas Islands, Gulf of GuineaPublication . Correia, Edna; Catry, Paulo; Sinclair, Frazer; Santos, Yodiney dos; Robalo, Joana; Lima, Cristina S.; Granadeiro, José PedroSeabirds are a highly threatened group, yet the foraging ecology of several species remains poorly understood. Brown boobies breed in all oceans in the tropical region and are common across their range. In Tinhosa Grande (São Tomé and Príncipe), this species breeds in one of the largest colonies of seabirds in the east tropical Atlantic. We studied the foraging ecology of Brown boobies from this colony during the chick-rearing period. Thirty-three birds were tracked with GPS loggers and their diet was analysed from 11 regurgitations, using traditional and DNA barcoding techniques for prey identifcation. A total of 127 completed foraging trips were identifed, 89% of which lasted less than 24 h. Females performed signifcantly longer trips and both sexes foraged preferentially over deep oceanic waters. The diet of Brown boobies included juvenile fsh and squid (Sthenoteuthis pteropus), comprising mostly fsh species whose juvenile phases live in the pelagic environment, and only migrate to coastal waters when adults. The most frequent of those prey found was Flying gurnard (Dactylopterus volitans). The relevance of such prey shows that Brown booby conservation depends not only on the management of their foraging areas and breeding sites but also on the correct management of the coastal adjacent areas that support the adult individuals of some of their prey. Our results suggest that the areas closest to the colony do not have available resources for these birds to feed on and that Brown boobies may be associate with subsurface marine predators or with sargassum patches to forage.
- Length-weight relationship of fish species from the Bijagós Archipelago, Guinea-BissauPublication . Correia, Edna; Granadeiro, José Pedro; Regalla, Aissa Said; Catry, PauloLength–weight relationships were estimated for six teleost fish species occurring in Bijagós Archipelago, Guinea-Bissau. Samples were collected seasonally during three dry seasons (2013/2014, 2014/2015, 2015/2016) and two rainy seasons (2015 and 2016). Fishes were captured by three methods: angled from the beach or a boat; using beach seine with a mesh size ranging 0.5–1 cm; drift netting from a boat (mesh size 2 cm). This work provides the length-weight relationship for three fish species that are not reported in FishBase (Citharichthys stampflii, Gerres nigri and Psettodes belcheri) as well as for three species from which we present a wider size range (Eucinostomus melanopterus, Scomberomorus tritor and Sphyraena afra).
- Predatory pelagic fishes of the Bijagós Archipelago (Guinea-Bissau) show high overlap in diets dominated by sardinellaPublication . Correia, Edna; Granadeiro, José Pedro; Regalla, Aissa Said; Dias, Emanuel; Almeida, Ana Pereira; Catry, PauloKnowledge of trophic interactions between the key components of marine communities is required to understand food-web dynamics and develop ecosystem-based management approaches. In West Africa, where fisheries sustain the livelihoods of a significant part of the human population, this understanding is even more urgent, especially in the face of rapidly expanding fisheries and some stock collapses in the region. We studied the feeding ecology of the Crevalle jack Caranx hippos, West African Spanish mackerel Scomberomorus tritor and Guinean barracuda Sphyraena afra in the Bijagós Archipelago, Guinea-Bissau. These are the most abundant pelagic predatory teleost fishes in the area, but little is known about their ecology despite being species with commercial and recreational value, and they likely also play an important role in various African coastal ecosystems. Our findings show a high degree of dietary overlap among these three predator species, despite some degree of segregation by prey size and type. All three predators depend on Sardinella maderensis as the most important prey, which together with other members of the Clupeidae represented 47–96% of the ingested prey items. There was little difference in the diets of the predators between the dry and rainy seasons. These novel findings suggest a ‘wasp-waist’-structured ecosystem in the Bijagós Archipelago in which S. maderensis is the central small-sized pelagic fish species, and stress the need for an ecosystem-based approach to fisheries management in the region, with precautionary measures taken to avoid the overexploitation of clupeids.
- The diet of two opportunistic seabirds (Caspian and Royal Terns) confirms the importance of Sardinella spp. in West African coastal food websPublication . Correia, Edna; Granadeiro, J. P.; Regalla, Aissa Said; Monteiro, Hamilton; Catry, PauloDespite their importance for fisheries, livelihoods and biodiversity conservation, shelf ecosystems in West Africa are poorly known. Caspian Tern (Hydroprogne caspia) and Royal Tern (Thalasseus maximus) are two of the most numerous and widespread nesting seabirds in the region, and an understanding of the diet of these opportunistic predators may throw light on important elements of the local food webs. This study describes and compares the prey consumed by these two species in Guinea and Guinea-Bissau collected from 2013 to 2015. Our results show that both tern species feed mostly on pelagic fish from which Clupeidae (mostly Sardinella maderensis) dominated the diet at all locations and seasons. Pristigasteridae and Polynemidae were the next most frequent prey in the diet of these two tern species. Our findings strengthen the recent suggestion of a wasp-waist ecosystem for our study area, with sardinella as the key prey for several predators, including seabirds and pelagic fishes, and potentially influencing their distribution and abundance. Moreover, our results show a higher diversity in the diet of the Caspian Tern, with this species preying on a greater range of benthopelagic fishes (e.g. Gerreidae; Mugilidae) which fits with observations of inshore foraging that seems rarer in Royal Terns. We further show that prey identification based only on otoliths from pellets, as opposed to the use of all hard structures (e.g. otoliths, vertebrae, scales), seriously underestimates the occurrence of species with fragile and small otoliths, including clupeids and other small pelagics.