DOCSLIB.ORG

The Recreational Fishery in the Kosi Estuarine Lake System, South Africa

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Recreational Fishery in the Kosi Estuarine Lake System, South Africa http://africanzoology.journals.ac.za The recreational fishery in the Kosi estuarine lake system, South Africa N.C. James1*, L.E. Beckley1, B.Q. Mann1 &R.Kyle2 1 Oceanographic Research Institute, P.O. Box 10712, Marine Parade, 4056 South Africa 2 KwaZulu-Natal Nature Conservation Service, P.O. Box 43, KwaNgwanase, 3973 South Africa Received 2 November 2000. Accepted 15 February 2001 The Kosi estuarine system, located in northern KwaZulu-Natal, is becoming an increasingly popular angling venue. Recreational catch card data from the National Marine Linefish System for the years 1986 to 1999 were analysed to determine total catch, catch composition, catch per unit effort (CPUE), seasonality of catches and annual trends in catch composition. A total of 17 families, comprising 34 species, was reported in catches of recreational anglers. Pomadasys spp., predominantly Pomadasys commersonnii, was the most prominent taxon caught in terms of both numbers and mass. Seasonal trends in catch rates were observed, with more fish caught in the summer and autumn months. The catch rate fluctuated annually. Fluctuations in CPUE were closely correlated to the number of cards collected, which reflects bias in the data. Despite annual fluctuations in CPUE, regression analysis revealed a slight increase in overall CPUE with time. However, CPUE for Acanthopagrus berda and Lutjanus argentimaculatus decreased steadily since 1986. The decline of these two estuarine-dependent species may indicate that the total fishing levels are not sustainable. Key words: angling, catch composition, catch per unit effort. INTRODUCTION (Makhawulani, Mpungwini and Nhlange). Since The Kosi estuarine system (Fig. 1), which consists 1950, there has been a camping facility, which is of four connected lakes, is located on the east coast used primarily by recreational anglers, on the of South Africa, and extends from 26°50’S to northwestern shore of Lake Nhlange (Kyle 1986). 27°11’S and 32°38’E to 32°53’E (Begg 1978). The Local children also fish by rod and line, but from system is approximately 10 km long and runs the banks of the system. Species caught by the parallel to the Indian Ocean, behind coastal children are generally small species which are not dunes. The four lakes drain through a perma- targeted by recreational anglers. The most com- nently open estuary, which opens to the sea 2 km monly caught species are the pouter (Gerres south of the Mozambique/South African border. acinaces) and Terapon jarbua, a species that is The southernmost lake, Amanzimnyama is com- viewed as a pest by recreational anglers (Kyle pletely fresh, but the other three lakes are influ- 1992). There is also a limited amount of recre- enced by the sea, and thus support euryhaline ational shore angling that takes place at the mouth fauna (Blaber 1978). The Kosi system is unique in of the system from the north bank. The small reef KwaZulu-Natal, in that it is a large clear-water sys- just inside the mouth and the beach south of the tem. The two small rivers which enter the system mouth fall into sanctuary areas closed to fishing. rise in leached acidic sands and, as a consequence, The diverse fish fauna supports a traditional trap carry little silt (Mountain 1990). fishery, a recreational fishery, and a recent gill net The clear water of the system, together with the fishery. The fish traps (kraals) are built in the proximity of the lakes to tropical waters, result in a estuary and Lake Makhawulani, which have diverse fish fauna (Blaber 1980). A total of 163 greater tidal flow (Kyle & Robertson 1997). Gill marine species has been recorded in the system. netting is only permitted at the margins of Lake The local Tonga inhabitants have fished in the Kosi Nhlange and away from any channel entrances system for centuries, using traps and traditional (Kyle 1999). Both the Kosi trap fishery and the gill spears. Recreational anglers began utilizing the net fishery have been studied (Kyle 1981, 1986, system towards the end of the 1940s, fishing 1999), but little research has been done on the from small boats in the three northern lakes recreational fishery in the Kosi estuarine system. This paper provides an analysis of recreational *Author for correspondence. E-mail: [email protected] angling in the Kosi estuarine system, based on 36(2): 217–228 (October 2001) http://africanzoology.journals.ac.za 218 African Zoology Vol. 36, No. 2, October 2001 a b Fig. 1. a, Location of the greater St Lucia Wetland Park in KwaZulu-Natal, South Africa; b, map of the Kosi estuarine lake system. catch card data from anglers based at the Nhlange fishing outing. The catch cards, which are available campsite. The Kosi estuarine system forms part at the fish cleaning site, are completed voluntarily of the Kosi Bay Nature Reserve, which was by anglers, and collected from the site by proclaimed in 1987, and has recently been incor- KZNNCS staff. Where possible, KZNNCS staff porated into the Greater St Lucia Wetland Park also visit the campsite to encourage and assist (GSLWP). The KwaZulu-Natal Nature Conserva- fishermen in filling out catch cards. There is no tion Service (KZNNCS) is the management cross-check on the accuracy of reporting. The authority responsible for the protection and man- angling details recorded are number of anglers per agement of the GSLWP, which was declared a boat, date, time spent fishing and catch (number World Heritage Site in 1999. and estimated mass per individual fish). Each catch card represents a complete angling outing. METHODS The completed catch cards are sent to the Oceano- Since 1986, recreational anglers at Kosi Bay have graphic Research Institute (ORI) in Durban, for been requested to complete catch cards after each entry onto the National Marine Linefish System http://africanzoology.journals.ac.za James et al.: Recreational fishery in the Kosi estuarine lake system 219 Table 1. Angling effort from the Kosi system between 1986 and 1999. Year Number of outings Number of anglers Number of hours Total number of recorded per outing per outing monitored hours (mean = 3.07 ± 0.25 S.D.) (mean = 5.3 ± 0.53 S.D.) 1986 510 3.7 5.4 2343 1987 991 3.1 4.9 4517 1988 1601 3.1 4.9 7674 1989 1181 3.0 5.1 5970 1990 1060 3.1 5.1 5370 1991 1312 3.0 5.0 6235 1992 1003 3.1 5.6 5265 1993 1973 2.9 5.2 10054 1994 2379 2.9 5.1 11619 1995 2288 2.9 5.2 11464 1996 1698 3.1 5.2 8223 1997 825 3.2 5.5 3916 1998 653 3.3 6.2 3611 1999 892 2.6 5.8 4824 (NMLS) database and subsequent analysis. a peak of 2379 in 1994, declining thereafter to 892 Recreational catch card data from 1986 to 1999 in 1999 (Table 1). The number of anglers per outing were analysed to determine total catch, catch varied little throughout the study period, with a composition, catch per unit effort (CPUE), season- mean of 3.07 anglers per outing (S.D. = 0.25). The ality of catches and annual trends in the numbers mean number of hours fished per outing was also and mass of important angling species. Owing to fairly stable throughout the study period, ranging the inability of fishermen to accurately identify all from 4.9 to 6.2 hours, with a mean of 5.3 hours per fish to species level, certain species were grouped outing (S.D. = 0.53). at genus level. The total number of monitored hours fished in a There are numerous biases in the voluntary year (Table 1) followed the same trends as the NMLS data, which can affect analyses. These number of angling outings reported and was biases include prestige bias, digit bias, uninten- highest between 1993 and 1996, and lowest at the tional misreporting, deliberate misreporting, beginning and end of the study period. Care apathy and non-response bias (Pollock et al. 1994). should be taken in interpreting these results as Prestige bias refers to the tendency of some they often reflect the amount of effort put into anglers to overestimate the number and size of collecting catch cards, rather than an actual fish caught, while digit bias occurs when anglers increase or decrease in angling effort. round up or round down the mass or number of CPUE was generally higher during the summer fish caught. Misreporting may be unintentional, as and autumn months (November to May) and anglers are often unable to distinguish between lowest during winter and spring (June to October) different fish species, or intentional out of fear of (Fig. 2). prosecution. Apathy in completing cards is also problematic. In addition, effort by and efficiency Catch composition of KZNNCS staff in collecting catch cards varied Based on the information provided by anglers, a with time. Some anglers were confused and total of 17 families and 34 species was recorded in entered shore fishing data on estuarine catch the catches from 1986 to 1999 (Table 2). Species cards. believed to have been caught by shore anglers were excluded from the analysis (Appendix 1). RESULTS Teleosts accounted for 33 of the species, while elasmobranchs were only represented by one spe- Angling effort cies. Fig. 3a,b depicts the catch composition for the The number of reported angling outings in- 14-year study period by numbers and mass, creased from 510, at the inception of the project, to respectively. Pomadasys (almost exclusively http://africanzoology.journals.ac.za 220 African Zoology Vol. 36, No. 2, October 2001 Fig. 2.Mean monthly CPUE (fish/angler/h) for all angling species reported on catch cards in the Kosi system between 1986 and 1999; error bars are the standard error of mean.
Load more

Recommended publications
  • Estuarine Fish Diversity of Tamil Nadu, India
    Indian Journal of Geo Marine Sciences Vol. 46 (10), October 2017, pp. 1968-1985 Estuarine fish diversity of Tamil Nadu, India H.S. Mogalekar*, J. Canciyal#, P. Jawahar, D.S. Patadiya, C. Sudhan, P. Pavinkumar, Prateek, S. Santhoshkumar & A. Subburaj Department of Fisheries Biology and Resource Management, Fisheries College & Research Institute, (Tamil Nadu Fisheries University), Thoothukudi-628 008, India. #ICAR-National Academy of Agricultural Research Management, Rajendranagar, Hyderabad-500 030, Telangana, India. *[E-Mail: [email protected]] Received 04 February 2016 ; revised 10 August 2017 Systematic and updated checklist of estuarine fishes contains 330 species distributed under 205 genera, 95 families, 23 orders and two classes. The most diverse order was perciformes with 175 species, 100 genera and 43 families. The top four families with the highest number of species were gobidae (28 species), carangidae (23 species), engraulidae (15 species) and lutjanidae (14 species). Conservation status of all taxa includes one species as endangered, five species as vulnerable, 14 near threatened, 93 least concern and 16 data deficient. As numbers of commercial, sports, ornamental and cultivable fishes are high, commercial and recreational fishing could be organized. Seed production by selective breeding is recommended for aquaculture practices in estuarine areas of Tamil Nadu. [Keywords: Estuarine fishes, updated checklist, fishery and conservation status, Tamil Nadu] Introduction significant component of coastal ecosystem due to The total estuarine area of Tamil Nadu their immense biodiversity values in aquatic was estimated to be 56000 ha, which accounts ecology. The fish fauna inhabiting the estuarine 3.88 % of the total estuarine area of India 1.
    [Show full text]
  • TNP SOK 2011 Internet
    GARDEN ROUTE NATIONAL PARK : THE TSITSIKAMMA SANP ARKS SECTION STATE OF KNOWLEDGE Contributors: N. Hanekom 1, R.M. Randall 1, D. Bower, A. Riley 2 and N. Kruger 1 1 SANParks Scientific Services, Garden Route (Rondevlei Office), PO Box 176, Sedgefield, 6573 2 Knysna National Lakes Area, P.O. Box 314, Knysna, 6570 Most recent update: 10 May 2012 Disclaimer This report has been produced by SANParks to summarise information available on a specific conservation area. Production of the report, in either hard copy or electronic format, does not signify that: the referenced information necessarily reflect the views and policies of SANParks; the referenced information is either correct or accurate; SANParks retains copies of the referenced documents; SANParks will provide second parties with copies of the referenced documents. This standpoint has the premise that (i) reproduction of copywrited material is illegal, (ii) copying of unpublished reports and data produced by an external scientist without the author’s permission is unethical, and (iii) dissemination of unreviewed data or draft documentation is potentially misleading and hence illogical. This report should be cited as: Hanekom N., Randall R.M., Bower, D., Riley, A. & Kruger, N. 2012. Garden Route National Park: The Tsitsikamma Section – State of Knowledge. South African National Parks. TABLE OF CONTENTS 1. INTRODUCTION ...............................................................................................................2 2. ACCOUNT OF AREA........................................................................................................2
    [Show full text]
  • A Retrospective Analysis of Shark Catches Made by Pelagic Longliners
    OCEANOGRAPHIC RESEARCH INSTITUTE, DURBAN, SOUTH AFRICA, AFFILIATED WITH THE UNIVERSITY OF KWAZULU-NATAL A retrospective analysis of shark catches made by pelagic longliners off the east coast of South Africa and biology and life history of shortfin mako shark, Isurus oxyrinchus Submitted in fulfillment of the academic requirements for the degree of Master of Science in the Oceanographic Research Institute, affiliated with the School of Biological and Conservation Sciences, University of KwaZulu-Natal, Durban. By Alan Foulis February 2013 i i. Abstract Oceanic pelagic shark species are under threat worldwide as fishing effort increases and they are taken as both targeted and bycatch. It is widely recognized that the life history characteristics of sharks make them inherently susceptible to over- exploitation and as a result many shark-directed fisheries have collapsed. It is therefore essential that good-quality data are collected and analyzed in order to provide fisheries managers with the right information to manage these species sustainably. South Africa has a pelagic longline fishery which includes tuna-, swordfish-, and shark-directed vessels. This study analyzed logbook (1998 – 2010) and observer data (2002 – 2010) provided by the Department of Agriculture, Forestry and Fisheries in order to assess the catch composition and standardized catch-per-unit-effort (CPUE) of sharks captured as both targeted catch and bycatch. The study area consisted of four zones moving east of the 20°E meridian: the Agulhas Bank (20°E – 24°E), South Coast (25°E – 29°E), East Coast 1 (30°E – 32.8°E), and East Coast 2 (32.9°E – 36.5°E).
    [Show full text]
  • Rapport (2.454Mb)
    NINA28 Report 55 Movements and area use by small spotted grunter (Pomadasys commersonnii) in the Great Fish Estuary (South Africa): implication for management T.F. Næsje, A.R. Childs, P.D. Cowley, E.B. Thorstad, F. Økland, S. Weerts and P. Buthelezi Øvre venstre hjørne på konvolutt Øvre venstre hjørne på konvolutt Øvre venstre hjørne på konvolutt E6/5 T EAMWORK E NTHUSIASM I NTEGRITY Q UALITY Cooperation and expertise for a sustainable future . Movements and area use by small spotted grunter (Pomadasys commersonnii) in the Great Fish Estuary (South Africa): implication for management T.F. Næsje1, A.R. Childs2, P.D. Cowley3, E.B. Thorstad1, F. Økland1, S. Weerts4 and P. Buthelezi4 1 Norwegian Institute for Nature Research (NINA), Tungasletta 2, NO-7485 Trondheim, Norway 2 Department of Ichthyology and Fisheries Science (DIFS), Rhodes University, P.O. Box 94, Grahamstown 6140, South Africa 3 South African Institute for Aquatic Biodiversity (SAIAB), Private Bag 1015, Grahamstown, South Africa 4 Zoology Department, University of Zululand, Private Bag X1001, KwaDlangezwa 3886, South Africa NINA Report 55 Næsje, T.F., Childs, A.R., Cowley, P.D., Thorstad, E.B., Økland, F., Weerts, S., and Buthelezi, P. 2005. Movements and area use by small spotted grunter (Pomadasys commersonnii) in the Great Fish Estuary (South Africa): implication for management. - NINA Report 55. 46 pp. Trondheim, May 2005 ISSN: 1504-3312 ISBN: 82-426-1588-8 (pdf) COPYRIGHT © Norwegian Institute for Nature Reseach (NINA) and South African Institute for Aquatic Biodiversity (SAIAB). The publication may be freely cited where the source is acknowledged. AVAILABILITY Open QUALITY CONTROLLED BY Odd Terje Sandlund, NINA RESPONSIBLE SIGNATURE Research director Odd Terje Sandlund (sign.) CLIENT(S) The South Africa / Norway Programme on Research Collaboration (National Research Foundation of South Africa, and Research Council of Norway) PHOTOES T.
    [Show full text]
  • MATURATION and SPAWNING of the SMALLSPOTTED GRUNT Pomadasys Commersonnii (LACEPÈDE, 1801) in the ARABIAN SEA OFF OMAN
    Thalassas, 27 (1): 67-79 An International Journal of Marine Sciences MATURATION AND SPAWNING OF THE SMALLSPOTTED GRUNT Pomadasys commersonnii (LACEPÈDE, 1801) IN THE ARABIAN SEA OFF OMAN A. AL-NAHDI, A. AL-MARZOUQI, N. JAYABALAN(1) & S. AL-HABSI Key words: Pomadasys commersonnii, Lm, GSI, relative condition, spawning, fecundity, sex-ratio, Arabian Sea, Oman ABSTRACT INTRODUCTION Observations on the maturation and spawning Fishes of the genus Pomadasys (Family: of the smallspotted grunt Pomadasys commersonnii Haemulidae) are represented by 11 species in caught from the Arabian Sea off Oman were made Omani waters (Fouda et al., 1997). The species between April 2005 and March 2007. While, males P. commersonnii popularly called smallspotted matured (50% maturity) at 44.2 cm TL, females grunt is one of the commonest fishes caught by matured at 42 cm TL. The population of P. the artisanal and industrial trawlers from Omani commersonnii spawned during June-December. The waters. The species is distributed along the northwest monthly gonado-somatic indices and the occurrence coast of India to the southern Oman, in the south of spent gonads coincided with the peak spawning to Seychelles, Madagascar and South Africa in the season. However, the monthly relative condition was coastal waters, estuaries, tidal fissures and even can not indicative of the spawning activity. Individual fish tolerate fresh water (Smith and Heemstra, 1986). spawned more than once a year. Fecundity ranged Besides forming a good recreational fishery (Smith from 214,510 to 1,421,520 eggs. Sex-ratio indicated and McKay, 1986; Mann et al., 2002), the species has homogeneous distribution of males and females in also been identified as a potent candidate for intensive the population.
    [Show full text]
  • Marine and Estuarine Fish Fauna of Tamil Nadu, India
    Proceedings of the International Academy of Ecology and Environmental Sciences, 2018, 8(4): 231-271 Article Marine and estuarine fish fauna of Tamil Nadu, India 1,2 3 1 1 H.S. Mogalekar , J. Canciyal , D.S. Patadia , C. Sudhan 1Fisheries College and Research Institute, Thoothukudi - 628 008, Tamil Nadu, India 2College of Fisheries, Dholi, Muzaffarpur - 843 121, Bihar, India 3Central Inland Fisheries Research Institute, Barrackpore, Kolkata - 700 120, West Bengal, India E-mail: [email protected] Received 20 June 2018; Accepted 25 July 2018; Published 1 December 2018 Abstract Varied marine and estuarine ecosystems of Tamil Nadu endowed with diverse fish fauna. A total of 1656 fish species under two classes, 40 orders, 191 families and 683 geranra reported from marine and estuarine waters of Tamil Nadu. In the checklist, 1075 fish species were primary marine water and remaining 581 species were diadromus. In total, 128 species were reported under class Elasmobranchii (11 orders, 36 families and 70 genera) and 1528 species under class Actinopterygii (29 orders, 155 families and 613 genera). The top five order with diverse species composition were Perciformes (932 species; 56.29% of the total fauna), Tetraodontiformes (99 species), Pleuronectiforms (77 species), Clupeiformes (72 species) and Scorpaeniformes (69 species). At the family level, the Gobiidae has the greatest number of species (86 species), followed by the Carangidae (65 species), Labridae (64 species) and Serranidae (63 species). Fishery status assessment revealed existence of 1029 species worth for capture fishery, 425 species worth for aquarium fishery, 84 species worth for culture fishery, 242 species worth for sport fishery and 60 species worth for bait fishery.
    [Show full text]
  • Pommadasys Commersonnii (Pisces: Haemulidae)
    STUDIES ON CAPTIVE REARING OF SPOTTED GRUNTER, POMMADASYS COMMERSONNII (PISCES: HAEMULIDAE) UNDER AMBIENT CONDITIONS. Submitted in Fulfilment of the . Requirements for the Degree of < MASTER OF SCIENCE of RHODES UNIVERSITY Grahamstown, South Africa by NTOBEKO BACELA April 1998. 11 My father remains my inspiration, sacrificed his family and ultimately, his life ...... 111 TABLE OF CONTENTS ACKNOWLEDGEMENTS ..................................................................................................... v ABSTRACT ............................................................................................................................. vi CHAPTER 1. INTRODUCTION........................................................................................... 1 CHAPTER 2. EXPERIMENTAL LOCATION, SYSTEMS AND GENERAL METHODS. Systems specifications ............................................................................................................ 10 Water quality ............................................................................................................................ 13 General experimental methods ................................................................................................. 13 Monitoring of fish performance ............................................................................................... 15 Statistical methods ................................................................................................................... 18 . CHAPTER 3. THE EFFECT OF STOCKING DENSITY ON THE GROWTH
    [Show full text]
  • The Guild Approach to Categorizing Estuarine Fish Assemblages
    The guild approach to categorizing estuarine fish assemblages: a global review Michael Elliott1, Alan K Whitfield2, Ian C Potter3, Stephen J M Blaber4, Digby P Cyrus5, Frank G Nordlie6 & Trevor D Harrison7 1Institute of Estuarine & Coastal Studies, University of Hull, Hull HU6 7RX, UK; 2South African Institute for Aquatic Biodiversity, Private Bag 1015, Grahamstown 6140, South Africa; 3Centre for Fish and Fisheries Research, School of Biological Sciences and Biotechnology, Murdoch University, Perth, Western Australia 6150, Australia; 4CSIRO Marine Laboratories, PO Box 120, Cleveland 4163, Queensland, Australia; 5Coastal Research Unit of Zululand, University of Zululand, Private Bag X1001, KwaDlangezwa 3886, South Africa; 6Department of Zoology, PO Box 118525, University of Florida, Gainesville, FL 32611-8525, USA; 7Environment and Heritage Service, Department of the Environment, Northern Ireland, Commonwealth House, 35 Castle Street, Belfast BT1 1GU, UK Abstract Correspondence: Many studies have recently described and interpreted the community structure and Michael Elliott, Institute of Estuarine function of fishes inhabiting estuaries and other transitional waters in terms of & Coastal Studies, categories or guilds. The latter describe the main features of the fishes’ biology and the University of Hull, way in which they use an estuary. However, the approach has been developed by Hull HU6 7RX, UK different workers in different geographical areas and with differing emphasis such that Tel.: +44 (0) 1482 there is now a need to review the guilds proposed and used worldwide. The previous 465503/464558 Fax: +44 (0) 1482 wide use of the guild approach has involved increasing overlap and/or confusion 464130 between different studies, which therefore increases the need for standardization while E-mail: mike.elliott@ at the same time providing the opportunity to reconsider the types and their use hull.ac.uk worldwide.
    [Show full text]
  • Biology and Demography of the Spotted Grunter
    BIOLOGY AND DEMOGRAPHY OF THE SPOTTED GRUNTER POMADASYS COMMERSONNII (HAEMULIDAE) IN SOUTH AFRICAN WATERS Submitted in fulfillment of the requirements for the degree of Master of Science of Rhodes University, Grahamstown, South Africa By Garth Anthony Webb August 2002 Abstract The spotted grunter, Pomadasys commersonnii (Haemulidae), is an Indian Ocean coastal species, extending from India to False Bay but is absent from the central Indian Ocean islands. Its taste and texture has made it one of the most important line fish species and is caught by recreational and subsistence fisherman along the entire east coast of South Africa. Because of its inshore distribution, reduced catch rates and estuarine dependence the species was de-commercialised in 1992. Since then it has been investigated as a candidate species for mariculture. All previous work on the biology of the species was undertaken on fish collected in KwaZulu-Natal in the mid 1970's. All other information has been incidental and formed part of other ecological studies. All management plans for this species have been based on these data. To develop a more comprehensive management plan that incorporates the entire population of spotted grunter, it was deemed necessary to reassess the biology (including feeding biology, age and growth and reproductive biology) as well as the demography of the population throughout its distributional range in South African waters. Analysis of the diet of spotted grunter, collected in estuaries, indicates that crustaceans form the bulk of the prey selected. Amphipods, mysids and estuarine brachyura predominate the diet of fish < 300 mm TL. At 200 mm TL fish start to prey on anomurans, which are extracted from their burrows using the 'blowing' feeding mechanism.
    [Show full text]
  • ORI Fish Fact Sheet
    FACT SHEET SPOTTED GRUNTER Pomadasys commersonnii Family: Haemulidae Other common names: Smallspotted grunter, Gespikkelde knorder, Inkolokolo One of the largest grunters with a distinctive, long, sloping forehead and a body that narrows towards the tail. Overall colour is silvery Description grey with numerous black spots on the sides. The spots do not extend onto the head. Tropical and warm temperate Western Indian Ocean from India to Distribution South Africa. Found along the entire eastern seabord of southern Africa as far south as False Bay in the Western Cape. Adults are found in estuaries and coastal waters over soft sediments. Habitat Juveniles also mainly found in estuaries and harbours but also in coastal embayments and shallow coastal waters. Diet of adult fish in estuaries consists of crustaceans and molluscs Feeding such as sand prawns, mud prawns and pencil bait. Juveniles consume bivalve siphon tips, small benthic crustaceans and polychaete worms. Despite making seaward migrations to spawn, spotted grunter are largely resident in one estuary. This species has been the subject of Movement extensive research using both external dart tagging and acoustic telemetry. www.saambr.org.za They reach maturity at 33-39 cm total length and an age of 3 years, with males maturing earlier than females. Spawning takes place in Reproduction spring and summer in close proximity to estuary mouths and harbours. They can reach a maximum size of 91 cm fork length and a weight of Age and growth 9.5 kg. They can reach a maximum age of 16 years. The South African stock is considered to be overexploited as a result of overfishing and estuarine degradation.
    [Show full text]
  • Estuarine Use by Spotted Grunter <I>Pomadasys Commersonnii</I> In
    African Journal of Marine Science ISSN: 1814-232X (Print) 1814-2338 (Online) Journal homepage: https://www.tandfonline.com/loi/tams20 Estuarine use by spotted grunter Pomadasys commersonnii in a South African estuary, as determined by acoustic telemetry A-R Childs , PD Cowley , TF Næsje , AJ Booth , WM Potts , EB Thorstad & F Økland To cite this article: A-R Childs , PD Cowley , TF Næsje , AJ Booth , WM Potts , EB Thorstad & F Økland (2008) Estuarine use by spotted grunter Pomadasyscommersonnii in a South African estuary, as determined by acoustic telemetry, African Journal of Marine Science, 30:1, 123-132, DOI: 10.2989/AJMS.2008.30.1.12.462 To link to this article: https://doi.org/10.2989/AJMS.2008.30.1.12.462 Published online: 08 Jan 2010. Submit your article to this journal Article views: 108 Citing articles: 18 View citing articles Full Terms & Conditions of access and use can be found at https://www.tandfonline.com/action/journalInformation?journalCode=tams20 African Journal of Marine Science 2008, 30(1): 123–132 Copyright © NISC Pty Ltd Printed in South Africa — All rights reserved AFRICAN JOURNAL OF MARINE SCIENCE EISSN 1814–2338 doi: 10.2989/AJMS.2008.30.1.12.462 Estuarine use by spotted grunter Pomadasys commersonnii in a South African estuary, as determined by acoustic telemetry A-R Childs1*, PD Cowley2, TF Næsje3, AJ Booth1, WM Potts2, EB Thorstad3 and F Økland3 1 Department of Ichthyology and Fisheries Science, Rhodes University, PO Box 94, Grahamstown 6140, South Africa 2 South African Institute for Aquatic Biodiversity, Private Bag 1015, Grahamstown 6140, South Africa 3 Norwegian Institute for Nature Research, Tungasletta 2, NO-7485, Trondheim, Norway * Corresponding author, e-mail: [email protected] Manuscript received September 2007; accepted January 2008 Factors influencing estuarine use and marine excur- environmental conditions.
    [Show full text]
  • Tides and Moon Drive Fish Movements in a Brackish Lagoon T ∗ Marco Milardi , Mattia Lanzoni, Anna Gavioli, Elisa Anna Fano, Giuseppe Castaldelli
    Estuarine, Coastal and Shelf Science 215 (2018) 207–214 Contents lists available at ScienceDirect Estuarine, Coastal and Shelf Science journal homepage: www.elsevier.com/locate/ecss Tides and moon drive fish movements in a brackish lagoon T ∗ Marco Milardi , Mattia Lanzoni, Anna Gavioli, Elisa Anna Fano, Giuseppe Castaldelli Department of Life Sciences and Biotechnology, University of Ferrara, Via Luigi Borsari 46, Ferrara, 44121, Italy ARTICLE INFO ABSTRACT Keywords: Brackish lagoons, on the edge between marine and freshwater ecosystems, are vulnerable aquatic environments Moon that act as nursery grounds for several of the most commercially exploited fish families. We used long-term Tide passive gear data, to investigate whether the moon and tides affected fish movement between inner and outer Shallow lagoon habitats in a Northern Mediterranean coastal lagoon. In particular, we used multivariate, threshold and non- Juvenile fishes linear correlation analyses to explore the relationship between fish catches and moon and tide variables in Movement transitional habitats, accounting for the presence of potential prey and other major temporal and environmental Grey shrimp variables. Fish movements between habitats were influenced by moon and tide factors, which had effects comparable to annual and seasonal variations, respectively. Overall, the magnitude of effects related to the moon parameters were smaller than most environmental parameters examined, but still larger than e.g. the presence of invertebrate prey (lagoon shrimp) or some of the tide factors. European flounder catches were positively cor- related with disk illumination, while sand and black goby were influenced by the moon phase. Other benthic and pelagic species showed no significant correlation.
    [Show full text]