Pub Date : 2022-10-02DOI: 10.2989/1814232X.2022.2130427
E. Gammon, C. Moloney, Marcus Lipinski
The composition of the diet of juvenile deep-water hake Merluccius paradoxus is described and compared for three body-condition groups (below-average, average, and above-average). Diet was analysed using three metrics: occurrence, numeric and gravimetric. Juvenile hakes were caught in January and February of 2012 by means of 28 trawl deployments from the RV Dr Fridtjof Nansen between Orange Banks and Hondeklip Bay on the west coast of southern Africa at depths of 30-232 m. The 300 individuals analysed were a representative sample of all juveniles caught (3 114 fish), ranging in length from 52 to 205 mm (average length 107 mm). Their diet consisted of the euphausiid Euphausia lucens, the hyperiid amphipod Themisto gaudichaudii, the stomatopod Pterygosquilla armata capensis, and mesopelagic fishes Maurolicus muelleri and Lampanyctodes hectoris. The only significant difference in diet between the body-condition groups was for euphausiids and hyperiid amphipods in the numeric metric. A new method of assessing fish condition using otolith weight was tested. Because of the large variability in the data and small sample size, this method could not be applied effectively in this study. However, otolith weight has potential as a new fish condition metric when the variability can be lowered.
{"title":"Diet and condition of juvenile deep-water hake Merluccius paradoxus on the west coast of southern Africa","authors":"E. Gammon, C. Moloney, Marcus Lipinski","doi":"10.2989/1814232X.2022.2130427","DOIUrl":"https://doi.org/10.2989/1814232X.2022.2130427","url":null,"abstract":"The composition of the diet of juvenile deep-water hake Merluccius paradoxus is described and compared for three body-condition groups (below-average, average, and above-average). Diet was analysed using three metrics: occurrence, numeric and gravimetric. Juvenile hakes were caught in January and February of 2012 by means of 28 trawl deployments from the RV Dr Fridtjof Nansen between Orange Banks and Hondeklip Bay on the west coast of southern Africa at depths of 30-232 m. The 300 individuals analysed were a representative sample of all juveniles caught (3 114 fish), ranging in length from 52 to 205 mm (average length 107 mm). Their diet consisted of the euphausiid Euphausia lucens, the hyperiid amphipod Themisto gaudichaudii, the stomatopod Pterygosquilla armata capensis, and mesopelagic fishes Maurolicus muelleri and Lampanyctodes hectoris. The only significant difference in diet between the body-condition groups was for euphausiids and hyperiid amphipods in the numeric metric. A new method of assessing fish condition using otolith weight was tested. Because of the large variability in the data and small sample size, this method could not be applied effectively in this study. However, otolith weight has potential as a new fish condition metric when the variability can be lowered.","PeriodicalId":7719,"journal":{"name":"African Journal of Marine Science","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2022-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43737572","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-10-02DOI: 10.2989/1814232X.2022.2126525
J. Mann-Lang, B. Mann, G. Jordaan, R. Daly
Scientific output has proven the value of the Oceanographic Research Institute’s Cooperative Fish Tagging Project (ORI-CFTP) to biological and fisheries research, with more than 95 published manuscripts based on data from the ORI-CFTP. This study reviews the project from the perspective of participating anglers. A total of 267 members of the ORI-CFTP responded to an online survey designed to gather data on the profile of tagging members, their preferred methods of communication, attitudes towards fish tagging and fish conservation in general, changes in angling behaviour since becoming a member of the project, and support for the continuation of the ORI-CFTP. The results reveal that the ORI-CFTP has indeed made a considerable contribution towards improving the conservation ethics and behaviour of marine recreational anglers in South Africa. Improved communication with anglers— both taggers and non-taggers—through the ORI-CFTP has the potential to amplify much-needed conservation information to the broader angling community and thereby enhance environmental awareness. Recommendations on how to improve the ORI-CFTP and other angling-related citizen science projects are provided.
{"title":"An assessment of the impact of participation in the Oceanographic Research Institute’s Cooperative Fish Tagging Project on angler attitudes and behaviour","authors":"J. Mann-Lang, B. Mann, G. Jordaan, R. Daly","doi":"10.2989/1814232X.2022.2126525","DOIUrl":"https://doi.org/10.2989/1814232X.2022.2126525","url":null,"abstract":"Scientific output has proven the value of the Oceanographic Research Institute’s Cooperative Fish Tagging Project (ORI-CFTP) to biological and fisheries research, with more than 95 published manuscripts based on data from the ORI-CFTP. This study reviews the project from the perspective of participating anglers. A total of 267 members of the ORI-CFTP responded to an online survey designed to gather data on the profile of tagging members, their preferred methods of communication, attitudes towards fish tagging and fish conservation in general, changes in angling behaviour since becoming a member of the project, and support for the continuation of the ORI-CFTP. The results reveal that the ORI-CFTP has indeed made a considerable contribution towards improving the conservation ethics and behaviour of marine recreational anglers in South Africa. Improved communication with anglers— both taggers and non-taggers—through the ORI-CFTP has the potential to amplify much-needed conservation information to the broader angling community and thereby enhance environmental awareness. Recommendations on how to improve the ORI-CFTP and other angling-related citizen science projects are provided.","PeriodicalId":7719,"journal":{"name":"African Journal of Marine Science","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2022-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49166640","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-10-02DOI: 10.2989/1814232X.2022.2143423
J. Azevedo e Silva, A. Almeida, M. Cravo, M. Pais, Y. Santos, J. Paula
Little is known about the ichthyofauna from intertidal rock pools of the west coast of Africa, especially in the Gulf of Guinea. Rock pools are characteristic habitats of the intertidal zone of structurally complex rocky shores, adding important niche space to coastal fish species. In this study, rock pools of three similar rocky shores of Príncipe Island were sampled to describe the composition, abundance and distribution of fish assemblages and their relation to parameters of pool structure (volume, depth), water mass (temperature, salinity and pH) and biology (algal and coral cover, and biological species richness). A total of 18 fish species and one leptocephalus larva of unknown species, representing 13 families, were observed during sampling. In decreasing order, the five-most-abundant species were the goby Bathygobius burtoni, night sergeant Abudefduf taurus, West African rockhopper Entomacrodus cadenati, sailfin blenny Microlipophrys velifer and Biafra doctorfish Prionurus biafraensis, which together represented 81% of the total number of fish recorded during this study. The four-most-abundant species also proved to be the better adapted to the range of conditions found in rock pools. Overall, larger rock pools with minimal biological cover and higher salinity were found to support higher fish abundance and species richness. Most species individually preferred rock pools with larger volumes, but some presented a degree of habitat specificity, such as the absence or presence of biological cover. Species that were more-active swimmers preferred deeper pools.
{"title":"Patterns of fish distribution in tropical rock pools at Príncipe Island, Gulf of Guinea","authors":"J. Azevedo e Silva, A. Almeida, M. Cravo, M. Pais, Y. Santos, J. Paula","doi":"10.2989/1814232X.2022.2143423","DOIUrl":"https://doi.org/10.2989/1814232X.2022.2143423","url":null,"abstract":"Little is known about the ichthyofauna from intertidal rock pools of the west coast of Africa, especially in the Gulf of Guinea. Rock pools are characteristic habitats of the intertidal zone of structurally complex rocky shores, adding important niche space to coastal fish species. In this study, rock pools of three similar rocky shores of Príncipe Island were sampled to describe the composition, abundance and distribution of fish assemblages and their relation to parameters of pool structure (volume, depth), water mass (temperature, salinity and pH) and biology (algal and coral cover, and biological species richness). A total of 18 fish species and one leptocephalus larva of unknown species, representing 13 families, were observed during sampling. In decreasing order, the five-most-abundant species were the goby Bathygobius burtoni, night sergeant Abudefduf taurus, West African rockhopper Entomacrodus cadenati, sailfin blenny Microlipophrys velifer and Biafra doctorfish Prionurus biafraensis, which together represented 81% of the total number of fish recorded during this study. The four-most-abundant species also proved to be the better adapted to the range of conditions found in rock pools. Overall, larger rock pools with minimal biological cover and higher salinity were found to support higher fish abundance and species richness. Most species individually preferred rock pools with larger volumes, but some presented a degree of habitat specificity, such as the absence or presence of biological cover. Species that were more-active swimmers preferred deeper pools.","PeriodicalId":7719,"journal":{"name":"African Journal of Marine Science","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2022-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45128017","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-10-02DOI: 10.2989/1814232X.2022.2141321
F. Youssef, B. Benmansouand, Z. Ramdane
Between 2015 and 2020, 2 092 specimens of cartilaginous fishes (Chondrichthyes: Elasmobranchii) belonging to eight species and five genera were sampled along the Tunisian coast and examined for their cymothoid parasites, Among the eight examined elasmobranch species, only three were infested, Five parasite species were identified: Anilocra physodes, Emetha audouini, Ceratothoa oestroides, C. parallela and Nerocila orbignyi, These parasites presented three maturation stages: ovigerous females of A.physodes and E. audouini, adult non-ovigerous females of N. orbignyi, and juvenile females of C. oestroides and C. parallela, Most of these parasitic isopods were found on a single host species except for the two Ceratothoa species. We report new host-parasite associations, including the presence of A. physodes and E.audouini on smooth-hound Mustelus mustelus, the occurrence of C. oestroides and N. orbignyi on cartilaginous fish species, and the presence of C. parallela on black smooth-hound Mustelus punctulatus and M. mustelus. Parasitological indices and the seasonal variation in prevalence of the collected cymothoids, as well as parasitic species richness, are presented.
{"title":"New host–parasite associations of Cymothoidae (Crustacea, Isopoda) infesting elasmobranch fishes in Tunisian waters","authors":"F. Youssef, B. Benmansouand, Z. Ramdane","doi":"10.2989/1814232X.2022.2141321","DOIUrl":"https://doi.org/10.2989/1814232X.2022.2141321","url":null,"abstract":"Between 2015 and 2020, 2 092 specimens of cartilaginous fishes (Chondrichthyes: Elasmobranchii) belonging to eight species and five genera were sampled along the Tunisian coast and examined for their cymothoid parasites, Among the eight examined elasmobranch species, only three were infested, Five parasite species were identified: Anilocra physodes, Emetha audouini, Ceratothoa oestroides, C. parallela and Nerocila orbignyi, These parasites presented three maturation stages: ovigerous females of A.physodes and E. audouini, adult non-ovigerous females of N. orbignyi, and juvenile females of C. oestroides and C. parallela, Most of these parasitic isopods were found on a single host species except for the two Ceratothoa species. We report new host-parasite associations, including the presence of A. physodes and E.audouini on smooth-hound Mustelus mustelus, the occurrence of C. oestroides and N. orbignyi on cartilaginous fish species, and the presence of C. parallela on black smooth-hound Mustelus punctulatus and M. mustelus. Parasitological indices and the seasonal variation in prevalence of the collected cymothoids, as well as parasitic species richness, are presented.","PeriodicalId":7719,"journal":{"name":"African Journal of Marine Science","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2022-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47935131","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-07-03DOI: 10.2989/1814232X.2022.2100825
S. Ahouansou Montcho, KV Salako, FJ Chadare, SC Gnansounou, Z. Sohou, P. Failler, R. G. Glèlè Kakaï, AE Assogbadjo
Small pelagic fish species contribute substantially to the food security and livelihoods of local communities in developing countries. In West Africa, and particularly in Benin, small pelagic fisheries attract many migrant fishers who are key actors in the sector. This study assessed the characteristics and sociocultural impacts of the small pelagic fishery in Benin using qualitative approaches, including focus group discussions (n = 9), in-depth interviews (n = 35), a literature review, direct observations and secondary data. The findings showed that indigenous fishers from Benin and foreign fishers from Ghana are the two major groups of migrant fishers involved in small pelagic fishing in Benin. These fishers mostly use three categories of fishing gear: gillnets, seine nets, and hooks and lines. Over the period 2014–2018 the annual catch fluctuated between 1 123 and 2 040 tonnes, with the peak catch recorded in 2018, with a commercial value of €3 030 587. Apart from migrant fishers, fishmongers constitute another important pillar of the value chain. Conflicts among migrant fishers in the sector in Benin are related to landing fees and fishing gears. We discuss the urgent need to give attention to the sector through quantitative research and law enforcement to ensure its sustainability.
{"title":"Characteristics and sociocultural impacts of small pelagic fishing by migrant fishers in Benin, West Africa","authors":"S. Ahouansou Montcho, KV Salako, FJ Chadare, SC Gnansounou, Z. Sohou, P. Failler, R. G. Glèlè Kakaï, AE Assogbadjo","doi":"10.2989/1814232X.2022.2100825","DOIUrl":"https://doi.org/10.2989/1814232X.2022.2100825","url":null,"abstract":"Small pelagic fish species contribute substantially to the food security and livelihoods of local communities in developing countries. In West Africa, and particularly in Benin, small pelagic fisheries attract many migrant fishers who are key actors in the sector. This study assessed the characteristics and sociocultural impacts of the small pelagic fishery in Benin using qualitative approaches, including focus group discussions (n = 9), in-depth interviews (n = 35), a literature review, direct observations and secondary data. The findings showed that indigenous fishers from Benin and foreign fishers from Ghana are the two major groups of migrant fishers involved in small pelagic fishing in Benin. These fishers mostly use three categories of fishing gear: gillnets, seine nets, and hooks and lines. Over the period 2014–2018 the annual catch fluctuated between 1 123 and 2 040 tonnes, with the peak catch recorded in 2018, with a commercial value of €3 030 587. Apart from migrant fishers, fishmongers constitute another important pillar of the value chain. Conflicts among migrant fishers in the sector in Benin are related to landing fees and fishing gears. We discuss the urgent need to give attention to the sector through quantitative research and law enforcement to ensure its sustainability.","PeriodicalId":7719,"journal":{"name":"African Journal of Marine Science","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2022-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44969754","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-07-03DOI: 10.2989/1814232X.2022.2108144
A. Govender, J. Groeneveld, SP Singh, S. Willows‐Munro
Metabarcoding to determine marine zooplankton species composition is a fast-developing method, yet to be fully standardised. DNA barcode reference libraries that link species to barcode sequences remain incomplete, taxonomically imprecise, and biased towards well-studied regions. We used metabarcoding to determine the decapod crustacean species present in the marine zooplankton off eastern South Africa, a region for which reference libraries are comparatively poor. Zooplankton communities were sampled with tow nets at stations on the shelf (20- and 50-m isobaths) and at the shelf edge (100- and 200-m isobaths), and the samples were processed using high-throughput sequencing technology. The cytochrome c oxidase subunit I (COI) gene region was used for taxonomic assignment of amplicon sequence variants to species level at 95% and 99% similarity to barcode records. Detected species were cross-referenced against occurrence records from the region. Eighty- one decapod species were detected at 95% sequence similarity, but this declined to 60 species at the stricter 99% threshold. False-positive identifications were reduced by 60%. True crabs (Brachyura) were proportionally over-represented; the ratios of prawns (Dendrobranchiata), lobsters (Achelata) and burrowing shrimp (Axiidea) were consistent with occurrence records; and true shrimps (Caridea) and hermit crabs (Anomura) were under-represented. Metabarcoding identified 19 tropical western Indian Ocean (WIO) species in the samples from eastern Africa, confirming a southwards dispersal of drifting phases through the Mozambique Channel. Congruence of WIO species with the Agulhas Bioregion (shelf-edge detections) and Delagoa Biozone (shallow detections) was consistent with the dispersal of tropical species in warmer water masses. Metabarcoding of marine zooplankton communities to obtain species-level information advances high-resolution ecological research in pelagic ecosystems.
{"title":"Metabarcoding of zooplankton confirms southwards dispersal of decapod crustacean species in the western Indian Ocean","authors":"A. Govender, J. Groeneveld, SP Singh, S. Willows‐Munro","doi":"10.2989/1814232X.2022.2108144","DOIUrl":"https://doi.org/10.2989/1814232X.2022.2108144","url":null,"abstract":"Metabarcoding to determine marine zooplankton species composition is a fast-developing method, yet to be fully standardised. DNA barcode reference libraries that link species to barcode sequences remain incomplete, taxonomically imprecise, and biased towards well-studied regions. We used metabarcoding to determine the decapod crustacean species present in the marine zooplankton off eastern South Africa, a region for which reference libraries are comparatively poor. Zooplankton communities were sampled with tow nets at stations on the shelf (20- and 50-m isobaths) and at the shelf edge (100- and 200-m isobaths), and the samples were processed using high-throughput sequencing technology. The cytochrome c oxidase subunit I (COI) gene region was used for taxonomic assignment of amplicon sequence variants to species level at 95% and 99% similarity to barcode records. Detected species were cross-referenced against occurrence records from the region. Eighty- one decapod species were detected at 95% sequence similarity, but this declined to 60 species at the stricter 99% threshold. False-positive identifications were reduced by 60%. True crabs (Brachyura) were proportionally over-represented; the ratios of prawns (Dendrobranchiata), lobsters (Achelata) and burrowing shrimp (Axiidea) were consistent with occurrence records; and true shrimps (Caridea) and hermit crabs (Anomura) were under-represented. Metabarcoding identified 19 tropical western Indian Ocean (WIO) species in the samples from eastern Africa, confirming a southwards dispersal of drifting phases through the Mozambique Channel. Congruence of WIO species with the Agulhas Bioregion (shelf-edge detections) and Delagoa Biozone (shallow detections) was consistent with the dispersal of tropical species in warmer water masses. Metabarcoding of marine zooplankton communities to obtain species-level information advances high-resolution ecological research in pelagic ecosystems.","PeriodicalId":7719,"journal":{"name":"African Journal of Marine Science","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2022-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43247060","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-07-03DOI: 10.2989/1814232X.2022.2101525
SM Hashim, A. Muthumbi, JM Githaiga, J. Okondo
Meiofauna communities were analysed from samples collected at four stations on the Kenyan continental shelf (Shimoni, Kwale, Mombasa and Kilifi) during the maiden cruise of the RV Mtafiti, 12–21 December 2015. Nematodes were identified to genus level, and their distribution and composition were mainly influenced by grain size distribution, a finding similar to studies in other areas with a similar grain size distribution (iso-communities). The southern stations (Shimoni and Kwale) had coarser sediments than the northern stations (Mombasa and Kilifi). The family Chromadoridae was dominant at Shimoni, while Cyatholaimidae dominated at Kwale. Mombasa was dominated by Chromadoridae, Cyatholaimidae and Oxystominidae, and Kilifi by Xyalidae. The dominant genera portrayed a trend similar to that observed in the families, in that the dominant genera were members of the dominant families. Spilophorella was dominant at Shimoni, and Paracanthonchus, Paracyatholaimus, Desmodora, Microlaimus and Draconema were dominant at Kwale and Mombasa. Microlaimus, Daptonema and Terschellingia represented the highest abundances at Kilifi. All stations were dominated by epistratum feeders. Selective deposit feeders were the second-most-dominant feeding guild at Mombasa and Kwale, whereas non-selective feeders had the second-highest abundance at Kilifi. The diversity index was highest at Mombasa and lowest at Shimoni, whereas dominance was highest at Shimoni and lowest at Mombasa.
{"title":"Nematode community structure and distribution along the Kenyan continental shelf","authors":"SM Hashim, A. Muthumbi, JM Githaiga, J. Okondo","doi":"10.2989/1814232X.2022.2101525","DOIUrl":"https://doi.org/10.2989/1814232X.2022.2101525","url":null,"abstract":"Meiofauna communities were analysed from samples collected at four stations on the Kenyan continental shelf (Shimoni, Kwale, Mombasa and Kilifi) during the maiden cruise of the RV Mtafiti, 12–21 December 2015. Nematodes were identified to genus level, and their distribution and composition were mainly influenced by grain size distribution, a finding similar to studies in other areas with a similar grain size distribution (iso-communities). The southern stations (Shimoni and Kwale) had coarser sediments than the northern stations (Mombasa and Kilifi). The family Chromadoridae was dominant at Shimoni, while Cyatholaimidae dominated at Kwale. Mombasa was dominated by Chromadoridae, Cyatholaimidae and Oxystominidae, and Kilifi by Xyalidae. The dominant genera portrayed a trend similar to that observed in the families, in that the dominant genera were members of the dominant families. Spilophorella was dominant at Shimoni, and Paracanthonchus, Paracyatholaimus, Desmodora, Microlaimus and Draconema were dominant at Kwale and Mombasa. Microlaimus, Daptonema and Terschellingia represented the highest abundances at Kilifi. All stations were dominated by epistratum feeders. Selective deposit feeders were the second-most-dominant feeding guild at Mombasa and Kwale, whereas non-selective feeders had the second-highest abundance at Kilifi. The diversity index was highest at Mombasa and lowest at Shimoni, whereas dominance was highest at Shimoni and lowest at Mombasa.","PeriodicalId":7719,"journal":{"name":"African Journal of Marine Science","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2022-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45324035","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-07-03DOI: 10.2989/1814232X.2022.2113140
Jemimah Etornam Kassah, J. Blay, I. Okyere, N. Lazar
Aspects of the reproductive biology of Atlantic chub mackerel Scomber colias are reported here based on data from random samples of artisanal fish landings from Ghana. The specimens were between 13.7 cm and 40.7 cm total length (TL), and both sexes matured at a mean length (L m50) of approximately 25 cm TL. An overall sex ratio of 1:1 was estimated for the population. Absolute fecundity of the fish ranged between 10 220 and 155 791 eggs (mean 48 238 [SE 2 324] eggs) in individuals measuring between 22.8 and 36.5 cm TL and weighing 104.3 to 525.3 g. Monthly variations in the gonadosomatic index and the proportion of fish with ripe gonads in the samples indicated the occurrence of spawning activities during two periods, March–April and June–August, the latter period of which coincided with the coastal upwelling season in Ghanaian waters. These findings are compared with those for chub mackerel from the northwestern and southwestern coasts of Africa. The results of this study will help inform the management of this small pelagic species in Ghana.
{"title":"Maturity length, fecundity and spawning season of Atlantic chub mackerel Scomber colias in the coastal waters of Ghana (west-central Gulf of Guinea)","authors":"Jemimah Etornam Kassah, J. Blay, I. Okyere, N. Lazar","doi":"10.2989/1814232X.2022.2113140","DOIUrl":"https://doi.org/10.2989/1814232X.2022.2113140","url":null,"abstract":"Aspects of the reproductive biology of Atlantic chub mackerel Scomber colias are reported here based on data from random samples of artisanal fish landings from Ghana. The specimens were between 13.7 cm and 40.7 cm total length (TL), and both sexes matured at a mean length (L m50) of approximately 25 cm TL. An overall sex ratio of 1:1 was estimated for the population. Absolute fecundity of the fish ranged between 10 220 and 155 791 eggs (mean 48 238 [SE 2 324] eggs) in individuals measuring between 22.8 and 36.5 cm TL and weighing 104.3 to 525.3 g. Monthly variations in the gonadosomatic index and the proportion of fish with ripe gonads in the samples indicated the occurrence of spawning activities during two periods, March–April and June–August, the latter period of which coincided with the coastal upwelling season in Ghanaian waters. These findings are compared with those for chub mackerel from the northwestern and southwestern coasts of Africa. The results of this study will help inform the management of this small pelagic species in Ghana.","PeriodicalId":7719,"journal":{"name":"African Journal of Marine Science","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2022-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46785053","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-07-03DOI: 10.2989/1814232X.2022.2104373
LR Harris, AL Skowno, K. Sink, L. van Niekerk, S. Holness, M. Monyeki, P. Majiedt
Ecosystem status assessments are generally separated into realm-specific analyses (terrestrial, freshwater, estuarine or marine), but without integrating these into a coherent assessment of coastal biodiversity across the land–sea interface. Trends in assessment indicators in coastal versus non-coastal areas have also rarely been considered. In this study we aimed to compile the first cross-realm national biodiversity assessment for the South African coast using three key indicators. The ecological condition, ecosystem threat status, and ecosystem protection level of coastal ecosystem types (n = 186) were determined and compared with those of non-coastal ecosystem types (n = 444). Nearly half (46.9%) of the South African coastal habitat has been degraded compared with 20% of non-coastal areas. Proportionately, there are three-times (60%) as many threatened coastal ecosystem types (or 55% by area) as there are threatened non-coastal ecosystem types (19%, 6% by area). Despite the impacted state of coastal biodiversity, protection levels are generally higher in the coastal zone (87% of ecosystem types have some protection) compared with non-coastal areas (75%), although fewer coastal ecosystem types have met their biodiversity targets (24%, vs 28% for non-coastal ecosystem types). These results illustrate the importance of using a cross-realm approach for status assessments, management and conservation of coastal biodiversity. The assessment methods described are flexible and widely applicable to other regions.
{"title":"An indicator-based approach for cross-realm coastal biodiversity assessments","authors":"LR Harris, AL Skowno, K. Sink, L. van Niekerk, S. Holness, M. Monyeki, P. Majiedt","doi":"10.2989/1814232X.2022.2104373","DOIUrl":"https://doi.org/10.2989/1814232X.2022.2104373","url":null,"abstract":"Ecosystem status assessments are generally separated into realm-specific analyses (terrestrial, freshwater, estuarine or marine), but without integrating these into a coherent assessment of coastal biodiversity across the land–sea interface. Trends in assessment indicators in coastal versus non-coastal areas have also rarely been considered. In this study we aimed to compile the first cross-realm national biodiversity assessment for the South African coast using three key indicators. The ecological condition, ecosystem threat status, and ecosystem protection level of coastal ecosystem types (n = 186) were determined and compared with those of non-coastal ecosystem types (n = 444). Nearly half (46.9%) of the South African coastal habitat has been degraded compared with 20% of non-coastal areas. Proportionately, there are three-times (60%) as many threatened coastal ecosystem types (or 55% by area) as there are threatened non-coastal ecosystem types (19%, 6% by area). Despite the impacted state of coastal biodiversity, protection levels are generally higher in the coastal zone (87% of ecosystem types have some protection) compared with non-coastal areas (75%), although fewer coastal ecosystem types have met their biodiversity targets (24%, vs 28% for non-coastal ecosystem types). These results illustrate the importance of using a cross-realm approach for status assessments, management and conservation of coastal biodiversity. The assessment methods described are flexible and widely applicable to other regions.","PeriodicalId":7719,"journal":{"name":"African Journal of Marine Science","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2022-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48744788","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-07-03DOI: 10.2989/1814232X.2022.2105949
B. Mghili, M. Analla, M. Aksissou
Although there is great fluctuation in annual recordings of jellyfish along the Moroccan Mediterranean coast and an absence of long-term datasets, there is a common perception that jellyfish numbers are rising. To better understand the possible economic losses sustained by Moroccan fisheries caused by the effects of jellyfish, we undertook a survey among fishers at the Atlantic port of Tangier and the Mediterranean port of M’diq. We focused on fishers’ perceptions about jellyfish blooms in Moroccan waters and whether and how blooms affect their fishing activities. Our findings confirm that blooms have negatively affected fishing activities over the past decade in the Moroccan Mediterranean, but that the degree of impact varies considerably by fishery and location. Of the total respondents at M’diq, 86% reported that jellyfish reduced their seasonal revenue. The species mainly responsible for these losses were Pelagia noctiluca, followed by Rhizostoma pulmo and Chrysaora hysoscella. The annual direct damage caused by jellyfish has been estimated to be as high as US$3.26 million per year for the fleet at the port of M’diq. When jellyfish outbreaks occur, fishers must spend time repairing nets damaged by jellyfish, which adds more than 1 783 person-hours of work per year.
{"title":"Estimating the economic damage caused by jellyfish to fisheries in Morocco","authors":"B. Mghili, M. Analla, M. Aksissou","doi":"10.2989/1814232X.2022.2105949","DOIUrl":"https://doi.org/10.2989/1814232X.2022.2105949","url":null,"abstract":"Although there is great fluctuation in annual recordings of jellyfish along the Moroccan Mediterranean coast and an absence of long-term datasets, there is a common perception that jellyfish numbers are rising. To better understand the possible economic losses sustained by Moroccan fisheries caused by the effects of jellyfish, we undertook a survey among fishers at the Atlantic port of Tangier and the Mediterranean port of M’diq. We focused on fishers’ perceptions about jellyfish blooms in Moroccan waters and whether and how blooms affect their fishing activities. Our findings confirm that blooms have negatively affected fishing activities over the past decade in the Moroccan Mediterranean, but that the degree of impact varies considerably by fishery and location. Of the total respondents at M’diq, 86% reported that jellyfish reduced their seasonal revenue. The species mainly responsible for these losses were Pelagia noctiluca, followed by Rhizostoma pulmo and Chrysaora hysoscella. The annual direct damage caused by jellyfish has been estimated to be as high as US$3.26 million per year for the fleet at the port of M’diq. When jellyfish outbreaks occur, fishers must spend time repairing nets damaged by jellyfish, which adds more than 1 783 person-hours of work per year.","PeriodicalId":7719,"journal":{"name":"African Journal of Marine Science","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2022-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43466681","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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