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Socio-Economic and Environmental Challenges of Small-Scale Fisheries: Prognosis for Sustainable Fisheries Management in Lake Kariba, Zambia

- Imbwae, Imikendu, Aswani, Shankar, Sauer, Warwick H H

  • Authors: Imbwae, Imikendu , Aswani, Shankar , Sauer, Warwick H H
  • Date: 2023
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/391422 , vital:68650 , xlink:href="https://doi.org/10.3390/su15043179"
  • Description: The Lake Kariba fishery is of regional importance; it accounts for 35% of the total Zambian fish production. However, emerging evidence in the recent decades suggests that the fishery is facing socio-economic and environmental challenges. Using Ostrom’s framework for analysing socio-ecological systems, we examined the social, economic, and environmental problems faced by the fishing communities in Lake Kariba. The framework links various social, economic, and ecological factors to devise a sustainable fisheries management plan. A combination of survey questionnaires, focus group discussions, observations, and key informant interviews were used to assess this sustainability challenge. The data collected were subjected to bivariate and descriptive analysis. The results obtained did not show a significant decline in fish production over the past 13 years (R2 Linear = 0.119, p = 0.248). However, the experts and the fishers have reported declining trends in valuable fish species such as Oreochromis mortimeri, compounded by the increased fishing efforts (X2 = 180.14, p value = ˂ 0.00001). The key threats identified include: overfishing, weak institutions, and the introduction of invasive fish species such as Oreochromis niloticus. This situation has raised fears of fish depletion among the stakeholders. Based on these results, we recommend stronger institutional collaboration among the stakeholders in the riparian states and education that illustrates the global value of fisheries for food security and biodiversity conservation in pursuing the United Nations Sustainable Development Goals.
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  • Date Issued: 2023

Transboundary Fisheries Management in Kavango–Zambezi Transfrontier Conservation Area (KAZA-TFCA): Prospects and Dilemmas

- Imbwae, Imikendu, Aswani, Shankar, Sauer, Warwick H H, Hay, Clinton J

  • Authors: Imbwae, Imikendu , Aswani, Shankar , Sauer, Warwick H H , Hay, Clinton J
  • Date: 2023
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/391433 , vital:68651 , xlink:href="https://doi.org/10.3390/su15054406"
  • Description: Inland fisheries in the Kavango–Zambezi Transfrontier Conservation Area (KAZA-TFCA) offer food security to the riverine communities across the region. They also contribute towards the attainment of the United Nations’ Sustainable Development Goals 1 and 15, which aim to alleviate poverty and maintain biodiversity conservation. Despite this significant role, the fisheries have suffered severe declines in the previous decades due to multiple factors, such as overfishing and poor legislation. Furthermore, climate change is exerting pressure by altering the ecology and productivity of the river systems. The unprecedented challenges of the COVID-19 pandemic have further constrained management efforts. Attempts to address these challenges have pointed towards transboundary fisheries management as a silver bullet in moving towards sustainable fisheries management. However, the implementation of this strategy in the region has encountered numerous roadblocks, thereby subjecting the river ecosystem to a wider environmental threat, with dire consequences on livelihoods. This paper reviews existing management and governance structures together with key informant interviews to elicit primary and secondary data essential for management at the regional level. The study identifies conflicting regulations, and inadequate policies and institutions across the region as major bottlenecks affecting the successful implementation of transboundary fisheries management. Finally, the paper offers some suggestions for the improvement of fisheries management in the region.
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  • Date Issued: 2023

Deep phylogeographic structure may indicate cryptic species within the Sparid genus Spondyliosoma:

- McKeown, Niall J, Gwilliam, Michael P, Healey, Amy J E, Skujina, Ilze, Potts, Warren M, Sauer, Warwick H H, Shaw, Paul W

  • Authors: McKeown, Niall J , Gwilliam, Michael P , Healey, Amy J E , Skujina, Ilze , Potts, Warren M , Sauer, Warwick H H , Shaw, Paul W
  • Date: 2020
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/158085 , vital:40147 , DOI: 10.1111/jfb.14316
  • Description: Two geographically nonoverlapping species are currently described within the sparid genus Spondyliosoma: Spondyliosoma cantharus (Black Seabream) occurring across Mediterranean and eastern Atlantic waters from NW Europe to Angola and S. emarginatum (Steentjie) considered endemic to southern Africa. To address prominent knowledge gaps this study investigated range‐wide phylogeographic structure across both species. Mitochondrial DNA sequences revealed deep phylogeographic structuring with four regionally partitioned reciprocally monophyletic clades, a Mediterranean clade and three more closely related Atlantic clades [NE Atlantic, Angola and South Africa (corresponding to S. emarginatum)]. Divergence and distribution of the lineages reflects survival in, and expansion from, disjunct glacial refuge areas. Cytonuclear differentiation of S. emarginatum supports its validity as a distinct species endemic to South African waters.
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  • Date Issued: 2020

Social capital reduces vulnerability in rural coastal communities of Solomon Islands:

- Malherbe, Willem, Sauer, Warwick H H, Aswani, Shankar

  • Authors: Malherbe, Willem , Sauer, Warwick H H , Aswani, Shankar
  • Date: 2020
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/150230 , vital:38951 , https://doi.org/10.1016/j.ocecoaman.2020.105186
  • Description: Rural island communities are generally regarded as the most vulnerable groups affected by climate change. This perception arises due to them often being in less developed areas with high levels of exposure to stressors, while reportedly lacking the means to cope with these stressors. Studies which use developed-country yardsticks, such as those used in past IPCC-based assessments, when measuring vulnerability in less developed states will however inevitably over-pronounce its effects in such areas. The sustainable livelihoods approach provides an alternate means of determining vulnerability using capital assets such as social capital. The presence of these assets enables communities to pursue diverse livelihood strategies which ultimately serve to reduce their vulnerability. This study seeks to measure attributes of social capital in five marine dependent communities of Solomon Islands.
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  • Date Issued: 2020

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

Comparative study of skipjack tuna Katsuwonus pelamis (Scombridae) fishery stocks from the South Atlantic and western Indian oceans

- Dahlet, Lol I, Downey-Breedt, Nicola, Arce, Gabriel, Sauer, Warwick H H, Gasalla, Maria A

  • Authors: Dahlet, Lol I , Downey-Breedt, Nicola , Arce, Gabriel , Sauer, Warwick H H , Gasalla, Maria A
  • Date: 2019
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/123988 , vital:35523 , https://doi.org/10.3989/scimar.04804.22C
  • Description: Temporal and spatial fluctuations in the abundance of oceanic pelagic populations spread geographically around the globe are common (Cushing 1975). The causes of these fluctuations may be exogenous (environmental or anthropogenic) or endogenous to the organism (e.g. ontogenetic drivers) (Ricker 1954). This scenario applies to some tuna stocks, including the skipjack tuna, Katsuwonus pelamis (Linnaeus, 1758), known as bonito-listrado in Brazil, katunkel, or ocean bonito in South Africa, and godhaa (bigger) or kadumas (smaller) skipjack in the Maldives. The skipjack belongs to the family Scombridae and inhabits tropical and subtropical areas of the globe. On average, 85% of skipjack catch occurs in waters warmer than 24°C (Fonteneau 2003). This resource is of particular importance, accounting for 57% of the global industrial tuna catch in 2016, and is mainly processed by the canning industry. Skipjack catches totaled 2.79 million t in 2016 (ISSF 2018), and currently 8.5% of worldwide catches are made by the pole-and line fleet. In Brazil and the Maldives, the resource is well-known. Catches in Brazil were seen to increase until 2014, while in the Maldives, 2006 marked the beginning of a strong and unsettling decline that continued until recent years. Off South Africa, skipjack catches are 1000 to 10000 times lower than those from Brazil and the Maldives, and the highest catches were recorded in 2012.
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  • Date Issued: 2019

Ecological connectivity between the areas beyond national jurisdiction and coastal waters: Safeguarding interests of coastal communities in developing countries

- Popova, Ekaterina, Vousden, David, Sauer, Warwick H H, Mohammed, Essam Y, Allain, Valerie, Downey-Breedt, Nicola, Fletcher, Ruth, Gjerde, Kristina M, Halpin, Patrick, Kelly, Stephen, Obura, David, Pecl, Gretta T, Roberts, Michael J, Raitsos, Dionysios E, Rogers, Alex, Samoilys, Melita, Sumaila , Ussif Rashid, Tracey, Sean, Yool, Andrew

  • Authors: Popova, Ekaterina , Vousden, David , Sauer, Warwick H H , Mohammed, Essam Y , Allain, Valerie , Downey-Breedt, Nicola , Fletcher, Ruth , Gjerde, Kristina M , Halpin, Patrick , Kelly, Stephen , Obura, David , Pecl, Gretta T , Roberts, Michael J , Raitsos, Dionysios E , Rogers, Alex , Samoilys, Melita , Sumaila , Ussif Rashid , Tracey, Sean , Yool, Andrew
  • Date: 2019
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/124331 , vital:35594 , https://doi.10.1016/j.marpol.2019.02.050
  • Description: The UN General Assembly has made a unanimous decision to start negotiations to establish an international, legally-binding instrument for the conservation and sustainable use of marine biological diversity within Areas Beyond National Jurisdiction (ABNJ). However, there has of yet been little discussion on the importance of this move to the ecosystem services provided by coastal zones in their downstream zone of influence. Here, we identify the ecological connectivity between ABNJ and coastal zones as critically important in the negotiation process and apply several approaches to identify some priority areas for protection from the perspective of coastal populations of Least Developed Countries (LDCs). Initially, we review the scientific evidence that demonstrates ecological connectivity between ABNJ and the coastal zones with a focus on the LDCs. We then use ocean modelling to develop a number of metrics and spatial maps that serve to quantify the connectivity of the ABNJ to the coastal zone. We find that the level of exposure to the ABNJ influences varies strongly between countries. Similarly, not all areas of the ABNJ are equal in their impacts on the coastline. Using this method, we identify the areas of the ABNJ that are in the most urgent need of protection on the grounds of the strength of their potential downstream impacts on the coastal populations of LDCs. We argue that indirect negative impacts of the ABNJ fishing, industrialisation and pollution, communicated via oceanographic, cultural and ecological connectivity to the coastal waters of the developing countries should be of concern.
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  • Date Issued: 2019

Governance mapping: a framework for assessing the adaptive capacity of marine resource governance to environmental change

- Dutra, Leo X C, Sporne, Ilva, Haward, Marcus, Aswani, Shankar, Cochrane, Kevern L, Frusher, Stewart, Gasalla, Maria A, Gianesella, Sônia M F, Grant, Tanith, Hobday, Alistair J, Jennings, Sarah M, Plagányi, Éva, Pecl, Gretta T, Salim, Shyam S, Sauer, Warwick H H, Taboada, Manuela B, Van Putten, Ingrid E

  • Authors: Dutra, Leo X C , Sporne, Ilva , Haward, Marcus , Aswani, Shankar , Cochrane, Kevern L , Frusher, Stewart , Gasalla, Maria A , Gianesella, Sônia M F , Grant, Tanith , Hobday, Alistair J , Jennings, Sarah M , Plagányi, Éva , Pecl, Gretta T , Salim, Shyam S , Sauer, Warwick H H , Taboada, Manuela B , Van Putten, Ingrid E
  • Date: 2019
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/145336 , vital:38429 , DOI: 10.1016/j.marpol.2018.12.011
  • Description: Marine social-ecological systems are influenced by the way humans interact with their environment, and external forces, which change and re-shape the environment. In many regions, exploitation of marine resources and climate change are two of the primary drivers shifting the abundance and distribution of marine living resources, with negative effects on marine-dependent communities. Governance systems determine ‘who’ makes decisions, ‘what’ are their powers and responsibilities, and ‘how’ they are exercised. Understanding the connections between the actors comprising governance systems and influences between governance and the environment is therefore critical to support successful transitions to novel forms of governance required to deal with environmental changes. The paper provides an analytical framework with a practical example from Vanuatu, for mapping and assessment of the governance system providing for management of coral reef fish resources. The framework enables a rapid analysis of governance systems to identify factors that can encourage, or hinder, the adaptation of communities to changes in abundance or availability of marine resources.
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  • Date Issued: 2019

Science in the service of society: Is marine and coastal science addressing South Africa's needs?

- Cochrane, Kevern L, Sauer, Warwick H H, Aswani, Shankar

  • Authors: Cochrane, Kevern L , Sauer, Warwick H H , Aswani, Shankar
  • Date: 2019
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/126071 , vital:35847 , https://doi.10.17159/sajs.2019/4418
  • Description: The modern world is confronted with many and diverse social and environmental challenges of high complexity. In South Africa, rapid and sustainable development is needed to address high levels of poverty and unemployment but this development has to take place in the context of an environment that is already severely impacted by human activities. Sound and relevant scientific input and advice, covering the full scope of each challenge, is essential for effective decisions and actions to address the needs. South Africa has the benefit of strong scientific capacity but the country’s National Development Plan reported that national research priorities were not always consistent with South Africa’s needs. We investigate the validity of that conclusion in the coastal and marine sciences by examining presentations made at the 2017 South African Marine Science Symposium on the theme of ‘Unlocking the ocean’s economic potential whilst maintaining social and ecological resilience’. Despite the theme, only 21% of the presentations were judged to be actionable and directly relevant to societal needs, as defined by the criteria used. Less than 7% were evaluated as being interdisciplinary within the natural sciences and approximately 10% were found to include both natural and human sciences. Poor representation by the human sciences was also noteworthy. This preliminary assessment highlights the need for an urgent review of the disciplinary representation and approaches in marine and coastal science in South Africa in the context of the priority practical needs of the country now and into the future.
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  • Date Issued: 2019

Tools to enrich vulnerability assessment and adaptation planning for coastal communities in data-poor regions: application to a case study in Madagascar

- Cochrane, Kevern L, Rakotondrazafy, H, Aswani, Shankar, Chaigneau, Tomas, Downey-Breedt, Nicola, Lemahieu, Anne, Paytan, Adina, Pecl, Gretta T, Plagányi, Éva, Popova, Elizaveta, Van Putten, Ingrid E, Sauer, Warwick H H, Byfield, Val, Gasalla, Maria A, Van Gennip, Simon J, Malherbe, Willem, Rabary, Andriantsilavo, Rabeariso, Ando, Ramaroson, N, Randrianarimanana, V, Scott, Lucy E P, Tsimanaoraty, P M

Assessment of the likely sensitivity to climate change for the key marine species in the southern Benguela system

- Ortega-Cisneros, Kelly, Yokwana, Sibusiso, Sauer, Warwick H H, Cochrane, Kevern L, James, Nicola C, Potts, Warren M, Singh, L, Smale, Malcolm J, Wood, A, Pecl, Gretta T

  • Authors: Ortega-Cisneros, Kelly , Yokwana, Sibusiso , Sauer, Warwick H H , Cochrane, Kevern L , James, Nicola C , Potts, Warren M , Singh, L , Smale, Malcolm J , Wood, A , Pecl, Gretta T
  • Date: 2018
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/123211 , vital:35415 , https://doi.10.2989/1814232X.2018.1512526
  • Description: Climate change is altering many environmental parameters of coastal waters and open oceans, leading to substantial present-day and projected changes in the distribution, abundance and phenology of marine species. Attempts to assess how each species might respond to climate change can be data-, resource- and time-intensive. Moreover, in many regions of the world, including South Africa, species may be of vital socioeconomic or ecological importance though critical gaps may exist in our basic biological or ecological knowledge of the species. Here, we adapt and apply a trait-based sensitivity assessment for the key marine species in the southern Benguela system to estimate their potential relative sensitivity to the impacts of climate change. For our analysis, 40 priority species were selected based on their socioeconomic, ecological and/or recreational importance in the system. An extensive literature review and consultation with experts was undertaken concerning each species to gather information on their life history, habitat use and potential stressors. Fourteen attributes were used to estimate the selected species’ sensitivity and capacity to respond to climate change. A score ranging from low to high sensitivity was given for each attribute, based on the available information. Similarly, a score was assigned to the type and quality of information used to score each particular attribute, allowing an assessment of data-quality inputs for each species. The analysis identified the white steenbras Lithognathus lithognathus, soupfin shark Galeorhinus galeus, St Joseph Callorhinchus capensis and abalone Haliotis midae as potentially the most sensitive species to climate-change impacts in the southern Benguela system. There were data gaps for larval dispersal and settlement and metamorphosis cues for most of the evaluated species. Our results can be used by resource managers to determine the type of monitoring, intervention and planning that may be required to best respond to climate change, given the limited resources and significant knowledge gaps in many cases.
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  • Date Issued: 2018

Genetic analysis reveals harvested Lethrinus nebulosus in the Southwest Indian Ocean comprise two cryptic species

- Healey, Amy J E, Gouws, Gavin, Fennessy, Sean T, Kuguru, Baraka, Sauer, Warwick H H, Shaw, Paul W, McKeown, Niall J

  • Authors: Healey, Amy J E , Gouws, Gavin , Fennessy, Sean T , Kuguru, Baraka , Sauer, Warwick H H , Shaw, Paul W , McKeown, Niall J
  • Date: 2018
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/124538 , vital:35626 , https://doi.10.1093/icesjms/fsx245
  • Description: This study initially aimed to investigate the genetic population/stock structuring of Lethrinus nebulosus in the Southwest Indian Ocean (SWIO) to inform management practices in light of emerging evidence of overharvesting of this species throughout its distribution. Adult samples were genotyped for 14 nuclear microsatellites and by sequencing fragments of the mtDNA control region and COI gene. A salient feature of the data was the congruent cyto-nuclear partitioning of samples into two high divergent, reciprocally monophyletic groups. This indicates that despite no a priori evidence, hitherto described L. nebulosus in the SWIO comprises two cryptic species that co-occur among southern samples. This intermingling indicates that, at least in southern samples, both species are being indiscriminately harvested, which may severely compromise sustainability. Limited microsatellite differentiation was detected within both species, though there was some evidence of isolation in the Mauritian population. In contrast, mtDNA revealed a pattern consistent with chaotic genetic patchiness, likely promoted by stochastic recruitment, which may necessitate a spatial bet-hedging approach to management to satisfy fishery management and conservation goals.
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  • Date Issued: 2018

Genomic analysis reveals multiple mismatches between biological and management units in yellowfin tuna (Thunnus albacares)

- Mullins, Rachel B, McKeown, Niall J, Sauer, Warwick H H, Shaw, Paul W

  • Authors: Mullins, Rachel B , McKeown, Niall J , Sauer, Warwick H H , Shaw, Paul W
  • Date: 2018
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/124549 , vital:35627 , https://doi.10.1093/icesjms/fsy102
  • Description: The South African (SAF) yellowfin tuna (Thunnus albacares) fishery represents a potential example of misalignment between management units and biological processes. The SAF fishery spans an operational stock with a boundary at 20_E, either side of which fish are considered part of Atlantic or Indian Ocean regional stocks. However, the actual recruitment of fish from Atlantic and Indian Ocean spawning populations into SAF waters is unknown. To address this knowledge gap, genomic analysis (11 101 SNPs) was performed on samples from Atlantic and Indian Ocean spawning sites, including SAF sites spanning the current stock boundary. Outlier loci conferred high discriminatory power to assignment tests and revealed that all SAF fish were assigned to the Indian Ocean population and that no Atlantic Ocean fish appeared in the SAF samples. Additionally, several Indian Ocean migrants were detected at the Atlantic spawning site demonstrating asymmetric dispersal and the occurrence of a mixed-stock fishery in Atlantic waters. This study highlights both the spatial inaccuracy of current stock designations and a misunderstanding of interactions between the underlying biological units, which must be addressed in light of local and global declines of the species. Specifically, the entire SAF fishery must be managed as part of the Indian Ocean stock.
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  • Date Issued: 2018

Global trends of local ecological knowledge and future implications

- Aswani, Shankar, Lemahieu, Anne, Sauer, Warwick H H

  • Authors: Aswani, Shankar , Lemahieu, Anne , Sauer, Warwick H H
  • Date: 2018
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/70504 , vital:29668 , https://doi.org/10.1371/journal.pone.0195440
  • Description: Local and indigenous knowledge is being transformed globally, particularly being eroded when pertaining to ecology. In many parts of the world, rural and indigenous communities are facing tremendous cultural, economic and environmental changes, which contribute to weaken their local knowledge base. In the face of profound and ongoing environmental changes, both cultural and biological diversity are likely to be severely impacted as well as local resilience capacities from this loss. In this global literature review, we analyse the drivers of various types of local and indigenous ecological knowledge transformation and assess the directionality of the reported change. Results of this analysis show a global impoverishment of local and indigenous knowledge with 77% of papers reporting the loss of knowledge driven by globalization, modernization, and market integration. The recording of this loss, however, is not symmetrical, with losses being recorded more strongly in medicinal and ethnobotanical knowledge. Persistence of knowledge (15% of the studies) occurred in studies where traditional practices were being maintained consiously and where hybrid knowledge was being produced as a resut of certain types of incentives created by economic development. This review provides some insights into local and indigenous ecological knowledge change, its causes and implications, and recommends venues for the development of replicable and comparative research. The larger implication of these results is that because of the interconnection between cultural and biological diversity, the loss of local and indigenous knowledge is likely to critically threaten effective conservation of biodiversity, particularly in community-based conservation local efforts.
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  • Date Issued: 2018

Integrated genetic and morphological data support eco‐evolutionary divergence of Angolan and South African populations of Diplodus hottentotus

- Gwilliam, Michael P, Winkler, Alexander C, Potts, Warren M, Santos, Carmen V D, Sauer, Warwick H H, Shaw, Paul W, McKeown, Niall J

  • Authors: Gwilliam, Michael P , Winkler, Alexander C , Potts, Warren M , Santos, Carmen V D , Sauer, Warwick H H , Shaw, Paul W , McKeown, Niall J
  • Date: 2018
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/124833 , vital:35702 , https://doi.10.1111/jfb.13582
  • Description: The genus Diplodus presents multiple cases of taxonomic conjecture. Among these the D. cervinus complex was previously described as comprising three subspecies that are now regarded as separate species: Diplodus cervinus, Diplodus hottentotus and Diplodus omanensis. Diplodus hottentotus exhibits a clear break in its distribution around the Benguela Current system, prompting speculation that Angolan and South African populations flanking this area may be isolated and warrant formal taxonomic distinction. This study reports the first integrated genetic [mitochondrial (mt)DNA and nuclear microsatellite] and morphological (morphometric, meristic and colouration) study to assess patterns of divergence between populations in the two regions. High levels of cytonuclear divergence between the populations support a prolonged period of genetic isolation, with the sharing of only one mtDNA haplotype (12 haplotypes were fully sorted between regions) attributed to retention of ancestral polymorphism. Fish from the two regions were significantly differentiated at a number of morphometric (69·5%) and meristic (46%) characters. In addition, Angolan and South African fish exhibited reciprocally diagnostic colouration patterns that were more similar to Mediterranean and Indian Ocean congeners, respectively. Based on the congruent genetic and phenotypic diversity we suggest that the use of hottentotus, whether for full species or subspecies status, should be restricted to South African D. cervinus to reflect their status as a distinct species-like unit, while the relationship between Angolan and Atlantic–Mediterranean D. cervinus will require further demo-genetic analysis. This study highlights the utility of integrated genetic and morphological approaches to assess taxonomic diversity within the biogeographically dynamic Benguela Current region.
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  • Date Issued: 2018

Population connectivity of an overexploited coastal fish, Argyrosomus coronus (Sciaenidae), in an ocean-warming hotspot

- Henriques, R, Potts, Warren M, Santos, Carmen V D, Sauer, Warwick H H, Shaw, Paul W

  • Authors: Henriques, R , Potts, Warren M , Santos, Carmen V D , Sauer, Warwick H H , Shaw, Paul W
  • Date: 2018
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/125720 , vital:35811 , https://doi.10.2989/1814232X.2018.1434090
  • Description: Anthropogenic activities are recognised as causing significant impacts to marine systems at multiple levels, ranging from habitat disturbance (Pauly et al. 2005) to overfishing (Sala and Knowlton 2006) and loss of genetic diversity (Pinsky and Palumbi 2014). Exploitation and harvesting in particular are known to strongly influence fish populations and their associated ecosystems (Pauly et al. 2005), and in combination with ongoing climate change can have compound effects on the viability and long-term survival of marine fishes (Last et al. 2011). Species can react to the impacts of climate change either by shifting their distributional range or by adapting to changing conditions through individual ecological plasticity and/or local population adaptation (Briggs 2011; Last et al. 2011). However, since ecological plasticity and local adaptation have strong genetic components, overharvesting has the potential to impact the long-term adaptive ability of marine fishes by decreasing the extant genetic diversity (Allendorf et al. 2014). Therefore, understanding the impact of exploitation on genetic diversity and population substructuring is critical for predicting the likely consequences of continued exploitation and climate change.
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  • Date Issued: 2018

Spermatophore dimorphism in the chokka squid Loligo reynaudii associated with alternative mating tactics

- Sato, Noriyosi, Iwata, Yoko, Shaw, Paul W, Sauer, Warwick H H

  • Authors: Sato, Noriyosi , Iwata, Yoko , Shaw, Paul W , Sauer, Warwick H H
  • Date: 2018
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/127070 , vital:35952 , https://doi.10.1093/mollus/eyy002
  • Description: Chokka squid (Loligo reynaudii) have characteristic alternative mating tactics: ‘consort’ males temporarily pair with and guard a female and transfer spermatophores onto her oviduct opening inside the mantle cavity, whereas ‘sneaker’ males rush towards a mating pair and transfer spermatophores onto the female’s buccal membrane near her sperm storage organ. Differences in mating behaviours and their related sperm-storage sites clearly constrain the fertilization process and can drive dimorphism between consort and sneaker males. The presence and character of male dimorphism has not yet been fully examined in this species, but consort males are commonly much larger than sneaker males. We observed clear dimorphism in spermatangia (the sperm mass ejaculated from the spermatophore), consistently associated with the two alternative sperm storage sites on the female’s body. Observations of spermatophores stored in the Needham’s sac of mature males confirmed that small males produce ‘sneaker-type’ spermatangia whereas larger males produce ‘consort-type’ spermatangia, and no individuals possessed both types. Therefore, by association, the mating tactic adopted (including the sperm deposition site used) by individual males can be determined from observation of their spermatangial type, without requiring direct behavioural observation of mating. This ability to infer information about mating tactic will improve our understanding of the reproductive system and mating dynamics in this species.
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  • Date Issued: 2018

Phylogeny of the Sepia officinalis species complex in the eastern Atlantic extends the known distribution of Sepia vermiculata across the Benguela upwelling region

- Healey, Amy J E, McKeown, Niall J, Potts, Warren M, de Beer, Chénelle L, Sauer, Warwick H H, Shaw, Paul W

  • Authors: Healey, Amy J E , McKeown, Niall J , Potts, Warren M , de Beer, Chénelle L , Sauer, Warwick H H , Shaw, Paul W
  • Date: 2017
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/125631 , vital:35802 , https://doi.10.2989/1814232X.2017.1371076
  • Description: Accurate species identification and biogeographic characterisation are fundamental for appropriate management of expanding cephalopod fisheries. This study addresses this topic within the common cuttlefish Sepia officinalis species complex (S. officinalis, S. hierredda and S. vermiculata), with an emphasis on occurrence in African waters. Tissue samples from the currently presumed distributions of S. vermiculata and S. hierredda (from South Africa and Ghana/Angola, respectively) were sequenced for the cytochrome c oxidase subunit I (COI) and the cytochrome b (cytb) genes of the mitochondrial genome and then compared to existing S. officinalis sequences. Three highly divergent and reciprocally monophyletic clades, corresponding to S. officinalis, S. hierredda and S. vermiculata, were resolved, representing the first molecular confirmation of the distinct species status of S. hierredda and S. vermiculata. The sequences also revealed that, contrary to expectations based on presently published information, all samples from southern Angola were S. vermiculata. These results indicate that the range of S. vermiculata extends beyond the currently described northern limit and that S. hierredda and S. vermiculata may be indiscriminately harvested in Angolan waters. Finer-scale patterns within S. vermiculata phylogeography also indicate that the Benguela Current System and/or other environmental factors serve to isolate northern and southern stocks.
  • Full Text:
  • Date Issued: 2017

From global to regional and back again: common climate stressors of marine ecosystems relevant for adaptation across five ocean warming hotspots

- Popova, Ekaterina, Yool, Andrew, Byfield, Valborg, Cochrane, Kevern, Coward, Andrew C, Salim, Shyam S, Gasalla, Maria A, Henson, S.A, Hobday, Alistair J, Pecl, Gretta T, Sauer, Warwick H H, Roberts, Michael J

  • Authors: Popova, Ekaterina , Yool, Andrew , Byfield, Valborg , Cochrane, Kevern , Coward, Andrew C , Salim, Shyam S , Gasalla, Maria A , Henson, S.A , Hobday, Alistair J , Pecl, Gretta T , Sauer, Warwick H H , Roberts, Michael J
  • Date: 2016
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/124514 , vital:35623 , https://doi.10.1111/gcb.13247
  • Description: Ocean warming ‘hotspots’ are regions characterized by above-average temperature increases over recent years, for which there are significant consequences for both living marine resources and the societies that depend on them. As such, they represent early warning systems for understanding the impacts of marine climate change, and test-beds for developing adaptation options for coping with those impacts. Here, we examine five hotspots off the coasts of eastern Australia, South Africa, Madagascar, India and Brazil. These particular hotspots have underpinned a large international partnership that is working towards improving community adaptation by characterizing, assessing and projecting the likely future of coastal-marine food resources through the provision and sharing of knowledge. To inform this effort, we employ a high-resolution global ocean model forced by Representative Concentration Pathway 8.5 and simulated to year 2099. In addition to the sea surface temperature, we analyse projected stratification, nutrient supply, primary production, anthropogenic CO2-driven ocean acidification, deoxygenation and ocean circulation. Our simulation finds that the temperature-defined hotspots studied here will continue to experience warming but, with the exception of eastern Australia, may not remain the fastest warming ocean areas over the next century as the strongest warming is projected to occur in the subpolar and polar areas of the Northern Hemisphere. Additionally, we find that recent rapid change in SST is not necessarily an indicator that these areas are also hotspots of the other climatic stressors examined. However, a consistent facet of the hotspots studied here is that they are all strongly influenced by ocean circulation, which has already shown changes in the recent past and is projected to undergo further strong change into the future. In addition to the fast warming, change in local ocean circulation represents a distinct feature of present and future climate change impacting marine ecosystems in these areas.
  • Full Text:
  • Date Issued: 2016

Global proliferation of cephalopods

- Doubleday, Zoë A, Prowse, Thomas A A, Arkhipkin, Alexander, Pierce, Graham J, Semmens, Jayson, Steer, Michael, Leporati, Stephen C, Lourenço, Sílvia, Quetglas, Antoni, Sauer, Warwick H H, Gillanders, Bronwyn M

  • Authors: Doubleday, Zoë A , Prowse, Thomas A A , Arkhipkin, Alexander , Pierce, Graham J , Semmens, Jayson , Steer, Michael , Leporati, Stephen C , Lourenço, Sílvia , Quetglas, Antoni , Sauer, Warwick H H , Gillanders, Bronwyn M
  • Date: 2016
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/124560 , vital:35628 , https://doi.10.1016/j.cub.2016.04.002
  • Description: Human activities have substantially changed the world’s oceans in recent decades, altering marine food webs, habitats and biogeochemical processes [1]. Cephalopods (squid, cuttlefish and octopuses) have a unique set of biological traits, including rapid growth, short lifespans and strong life-history plasticity, allowing them to adapt quickly to changing environmental conditions [2–4]. There has been growing speculation that cephalopod populations are proliferating in response to a changing environment, a perception fuelled by increasing trends in cephalopod fisheries catch [4,5]. To investigate long-term trends in cephalopod abundance, we assembled global time-series of cephalopod catch rates (catch per unit of fishing or sampling effort). We show that cephalopod populations have increased over the last six decades, a result that was remarkably consistent across a highly diverse set of cephalopod taxa. Positive trends were also evident for both fisheries-dependent and fisheries independent time-series, suggesting that trends are not solely due to factors associated with developing fisheries. Our results suggest that large-scale, directional processes, common to a range of coastal and oceanic environments, are responsible. This study presents the first evidence that cephalopod populations have increased globally, indicating that these ecologically and commercially important invertebrates may have benefited from a changing ocean environment.
  • Full Text:
  • Date Issued: 2016
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