Ocean safaris or food: characterizing competitive interactions between recreational and artisanal billfish fisheries on the coast of Kenya

Diversity and Distributions

et al. 2022

Self Cite

Background and aim: Billfish are epipelagic marine predators facing increasing pressures such as overfishing and rising global temperatures. Overfishing is a major concern, as they are caught by industrial longline fishers targeting tuna. Billfish are targeted by multiple fishing sectors, which provides food, socio-economic and cultural benefits. To support effective billfish management and conservation, it is essential to understand their spatial distribution and the environmental factors that may influence it. Location:The focus of this study is the Indian Ocean (IO), where there are gaps in understanding the interactions between fisheries and billfish distribution. Three of six billfish species are at risk from overfishing. Therefore, determining their distribution is crucial to their management and conservation.Methods: Using Ocean Biogeographic Information System (OBIS) occurrence data, Indian Ocean Tuna Commission (IOTC) catch data, and environmental covariates, we applied species distribution models to investigate the spatial extent of the realized niches of six billfish species in the IO. We also determined the role and relative importance of environmental drivers. Moreover, we evaluated the association between species' spatial distribution and the fishing effort distribution. Results:We found niche partitioning and overlap among the six species identified spatial distribution, with higher species richness in the northern region of the IO and off the East coast of Africa. Temperature, mixed layer depth and salinity were identified as the most important predictors of species distribution, with moderately warm and stable environments preferred by most billfish species. Areas with high species richness and high fishing effort overlap were primarily found in the Areas Beyond National Jurisdiction (ABNJ). In contrast, areas with high species diversity richness and low fishing effort were found mainly in the Exclusive Economic Zone (EEZ). Main conclusion: Spatial overlap between fishing effort and billfish projected distribution suggests inadvertent fishing pressure on billfish populations as they are caught together with targeted tuna. Spatial distribution transcends maritime zones, | 1555 THOYA eT Al.

Section: Discussionmentioning

confidence: 98%

Environmental controls of billfish species in the Indian Ocean and implications for their management and conservation

Thoya

Diversity and Distributions

et al. 2022

Self Cite

“…As demonstrated by the availability of tagging data on billfish from sport fisheries, states will need to support citizen science to ensure biological, conventional tagging, and basic research can continue. Critical assessments of available tagging data are required to facilitate dialogue between the sport fishing community and decision makers to address short- and long-term challenges arising from competitive interactions between billfish resource users (Kadagi et al 2021a , b ). Further, fishing operations are crucial for the socio-economic and cultural well-being of coastal communities across the WIO.…”

Section: Discussionmentioning

confidence: 99%

“…The WIO region has a long-established and internationally recognized recreational and sport fishery particularly in Kenya, Seychelles, Mozambique, Mauritius, La Reunion, and South Africa (Pepperell et al 2017 ; Kadagi et al 2021a , b ). Sport fishing clubs, tagging programmes and individual captains have kept detailed records of billfish catch, tag and release for several years.…”

Section: Billfish In the Wio Regionmentioning

confidence: 99%

“…The socio-economic and cultural importance of billfish species in the Western Indian Ocean (WIO) region has increasingly received attention (Harris et al 2013 ; Pepperell et al 2017 ; Kadagi et al 2020 ). Historically, these valuable fisheries are highly sought after by sport fisheries in several WIO countries such as Kenya (Ndegwa and Herrera 2011 ; Ndegwa and Kirathe 2015 ; Kadagi et al 2021a , b ), Mozambique (Mutombene 2013 ; Chassot et al 2019 ), La Réunion (Fleury et al 2012 ) and South Africa (Dunlop and Mann 2013 ). Billfish are also caught in artisanal fisheries for food and income while swordfish are commercially important in large-scale industrial fishing fleets.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Status and challenges for sustainable billfish fisheries in the Western Indian Ocean

Rev Fish Biol Fisheries

Mann

et al. 2022

Self Cite

Billfish species (families Istiophoridae and Xiphiidae) are caught in artisanal, recreational, and commercial fisheries throughout the Western Indian Ocean region. However, data and information on the interactions among these fisheries and the ecology of billfish in the WIO are not well understood. Using an in-depth analysis of peer-reviewed articles, grey literature, observation studies, and authors’ insider knowledge, we summarize the current state of knowledge on billfish fisheries in 10 countries. To describe historical and current trends, we examined fisheries statistics from governmental and non-governmental agencies, sportfishing clubs’ reports, diaries of sportfishing captains, and the catch and effort databases of the Indian Ocean Tuna Commission. We highlight two key points. First, billfish fisheries in the Western Indian Ocean are highly diverse, comprising two distinct segments—coastal and oceanic. However, data are poor for most countries with significant gaps in information especially for sport and artisanal fisheries. Second, the evidence assembled showed that billfish species have immense social, cultural, and economic value. Swordfish are targeted by both large-scale and semi-industrial fisheries, while other billfish species, particularly marlin, are highly sought after by sport fisheries in most countries. Our paper provides a comprehensive review of billfish fisheries and available information in the context of the WIO underscoring the need to strengthen data collection and reporting, citizen science, and collaborative sustainable development and management of billfish. Supplementary Information The online version contains supplementary material available at 10.1007/s11160-022-09725-8.

“…The likely future shift by SSF from small, mostly traditional fishing gears and vessels, to more modern vessels using bigger engines and mechanized gear, and the resultant increase in fishing power, may further increase the pressure on species highly susceptible to overfishing, such as sharks, as occurred in the Maldives and Madagascar (Ali, 2015; Tuda & Wolff, 2015; Humber et al, 2017). Secondly, the evidence that recreational fisheries may impact shark species, especially in Oceania and South America (Freire et al, 2020), presents a management challenge in the face of overlapping and competing fisheries resource uses, particularly since the small‐scale and recreational fisheries have an overlap in the species that they catch (Kadagi et al, 2021a; Kadagi et al, 2021b). The adoption of catch and release as well as voluntary tagging programmes demonstrate the potential of such programmes for data collection and the conservation of sharks.…”

Section: Implications For the Conservation And Management Of Sharksmentioning

confidence: 99%

Integrating long‐term citizen science data and contemporary artisanal fishery survey data to investigate recreational and small‐scale shark fisheries in Kenya

Everett

et al. 2022

Aquatic Conservation

Self Cite

1. Shark catches are common in small-scale (artisanal) and recreational fisheries; the magnitudes of these catches remain poorly known and understudied, particularly in developing countries. Data from three sources were used to assess the composition of shark landings in these fisheries in Kenya: boat-based recreational fishery tagging 1987-2016; observed landings from the Bycatch Assessment and Mitigation in the Western Indian Ocean Fisheries Project 2016-2017; and Catch Assessment Surveys landings data 2017-2020.2. Eighteen species were identified among 1,215 sharks recorded in small-scale fisheries between June 2016 and June 2017. Most of them belonged to the families Carcharhinidae (26%), Triakidae (23%) and Sphyrnidae (14%). Longlines (41%), drift gillnets (30%) and bottom-set gillnets (21%) recorded the highest proportions of catches.3. A total of 501 sharks comprising 16 species were recorded in the recreational tagging data between 1987 and 2016, caught using either trolling lines or rods and reels. The families Carcharhinidae (56%) and Sphyrnidae (12%) represented the highest proportion of the catch. 4. A generalized linear model was used to assess the effect of year, gear type, season and vessel propulsion mode on the variation in catches of sharks in smallscale fisheries between 2017 and 2020. Catches were significantly higher in 2017 with high catch rates observed in longlines and handlines.5. Findings from this study highlight the importance of citizen science by recreational fishers in increasing awareness around the risks and threats to shark populations. Strengthening of existing monitoring of shark interactions with smallscale and recreational fisheries is important alongside the implementation of appropriate conservation and management measures such as reductions in fishing effort (e.g. prawn trawling) in nursery areas, prohibiting the capture of CITESprotected species, and enforcing catch-and-release practices by sport fishers to ensure the long-term sustainability of both the affected shark species and the livelihoods of the fishers.