title: Data-Limited Population-Status Evaluation of Two Coastal Fishes in Southern Angola Using Recreational Catch Length-Frequency Data.
abstract: Excessive truncation of a population's size structure is often identified as an important deleterious effect of exploitation, yet the effect on population persistence of size-structure truncation caused by exploitation is often not quantified due to data limitations. In this study, we estimate changes in eggs per recruit (EPR) using annual length-frequency samples over a 9 year period to assess persistence of the two most important recreational fishes in southern Angola: west coast dusky kob (Argyrosomus coronus) and leerfish (Lichia amia). Using a length- and age-structured model, we improve on an existing method to fit this type of model to length-frequency data and estimate EPR. The objectives of the methodological changes are to add flexibility and robustness to the approach for assessing population status in data-limited situations. Results indicate that dusky kob presents very low levels of EPR (5%-10% of the per recruit reproductive capacity in the absence of fishing) in 2013, whereas large inter-annual variability in leerfish estimates suggest caution must be applied when drawing conclusions about its exploitation status. Using simulated length frequency data with known parameter values, we demonstrate that recruitment decline due to overexploitation leads to overestimation of EPR values. Considering the low levels of EPR estimated for the study species, recruitment limitation is not impossible and true EPR values may be even lower than our estimates. It is, therefore, likely that management action, such as the creation of Marine Protected Areas, is needed to reconstitute the west coast dusky kob population.
authors.affiliation: UMR 212 EME, Centre de Recherche Halieutique Méditerranéenne et Tropicale, Institut de Recherche pour le Développement (IRD), Sète, France.|Department of fisheries, Virginia Institute of Marine Science (VIMS), College of William & Mary, Gloucester Point, Virginia, United States of America.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Beckensteiner
authors.affiliation: UMR 212 EME, Centre de Recherche Halieutique Méditerranéenne et Tropicale, Institut de Recherche pour le Développement (IRD), Sète, France.|Department of fisheries, Virginia Institute of Marine Science (VIMS), College of William & Mary, Gloucester Point, Virginia, United States of America.
authors.forename: David M
authors.initials: DM
authors.lastname: Kaplan
authors.affiliation: Department of Ichthyology and Fisheries Science, Rhodes University, Grahamstown, South Africa.
authors.forename: Warren M
authors.initials: WM
authors.lastname: Potts
authors.affiliation: Faculdade Ciêncas da Universidade Agostinho Neto (FCUAN), Luanda, Angola.
authors.forename: Carmen V
authors.initials: CV
authors.lastname: Santos
authors.affiliation: Department of Wildlife, Fish and Conservation Biology, University of California, Davis, Davis, CA, United States of America.
authors.forename: Michael R
authors.initials: MR
authors.lastname: O'Farrell
mesh_terms: D000810:Angola; D000818:Animals; D003198:Computer Simulation; D017753:Ecosystem; D005398:Fisheries; D005399:Fishes / Q000502:physiology*; D005843:Geography; D016013:Likelihood Functions; D008962:Models, Theoretical; D009026:Mortality; D010063:Ovum / Q000502:physiology; D011157:Population Dynamics; D011998:Recreation; D013223:Statistics as Topic
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