Size structure and gear selectivity of target species in the multispecies
multigear fishery of the Kenyan South Coast
Paul M. Tuda
a, b, *
, Matthias Wolff
a
, Annette Breckwoldt
a
a
Leibniz Centre for Tropical Marine Ecology (ZMT) GmbH, Fahrenheitstrasse 6, 28359 Bremen, Germany
b
Faculty of Biology & Chemistry (FB2), University of Bremen, P.O Box 33 04 40, 28334 Bremen, Germany
article info
Article history:
Received 13 November 2015
Received in revised form
11 April 2016
Accepted 4 June 2016
Keywords:
Kenya
Gear selectivity
Artisanal
Reef
Multispecies
abstract
Multispecies fisheries commonly target those species and sizes that provide highest revenues (due to
both their high abundances and market values) using multiple gears. Yet most tropical countries still
apply single species management approaches, which ignore species - species and species - gear in-
teractions in these complex fisheries. The objective of the here presented study was to evaluate the role
and importance of the different fishing gears for the exploitation of the different species and sizes of the
artisanal reef fishery catch from the Kenyan South Coast. Like in most tropical multi-species fisheries, the
artisanal catch was characterized by a very large number of species (138 species representing 38 fam-
ilies). Of these, 17 species dominated the catch making up 91% of the overall abundance and 70% by
weight of the total catch from all gears. Species belonging to the families Siganidae, Scaridae and
Lethrinidae dominated the catch of most gears. Species selectivity by gear was determined by a classi-
fication analysis (hierarchical agglomerative clustering) based on a similarity matrix from transformed
abundance data of the fish species by gear. At a similarity of 50%, five groups were differentiated by the
cluster dendrogram. Considerable species and size overlap was observed between gears with the basket
trap and beach seine showing very similar selectivity with the composition of their catches to a large
extent being complementary. Overall the beach seine landed the smallest individuals in the catch with
the key species captured being smaller than the size at first maturity but only contributed 10% of the total
biomass landed compared to the basket traps which also targeted similar size ranges but at higher
relative abundance and biomass. The hook and line method and the ring net targeted the largest in-
dividuals in the catch but the hook and line contributed more in terms of the total biomass landed (31%).
Our findings indicate that the current fishing practices exploit fish species of small sizes but also small to
medium sized specimens relative to the species potential maximum size. Therefore, fishers by diversi-
fying their gears and strategies, have been able to target a significant part of the entire fish assemblage
(species and sizes) with each gear imposing different fishing mortalities on the target species. This
fishery strategy is a major challenge to decision-makers, and it is evident that the current regulations
focusing on gear restrictions are not adequate to manage this complex and highly effective fishery. Thus,
our proposal is that in addition to the current measures, an attempt should be made towards an inte-
grated approach that incorporates the fishing dynamics and distribution of effort across different gears
while complementing these with market based regulatory measures. Therefore, an important next step
in the analysis of the fishery of Kenya’s coast should be the determination of the present exploitation rate
of the target species along the resource size spectrum both temporally and spatially to provide a proper
assessment of the fisheries and provide a more succinct management advice towards reallocation of
fishing effort among alternative target species in this multispecies fisheries.
© 2016 Elsevier Ltd. All rights reserved.
1. Introduction
Artisanal fishing is one of the most important exploitative ac-
tivities on coral reefs sustaining many coastal communities in the
tropics (Russ and Alcala, 1989; Sadovy, 2005). Estimated to account
* Corresponding author. Leibniz Centre for Tropical Marine Ecology (ZMT) GmbH,
Fahrenheitstrasse 6, 28359 Bremen, Germany.
E-mail address: ptuda@yahoo.com (P.M. Tuda).
Contents lists available at ScienceDirect
Ocean & Coastal Management
journal homepage: www.elsevier.com/locate/ocecoaman
http://dx.doi.org/10.1016/j.ocecoaman.2016.06.001
0964-5691/© 2016 Elsevier Ltd. All rights reserved.
Ocean & Coastal Management 130 (2016) 95e106