Environ Biol Fish (2012) 95:227–236 DOI 10.1007/s10641-012-9985-5
Maintaining fish diversity in Thailand: variations in foraging behavior Patchara Nithirojpakdee & F. William H. Beamish & David L. G. Noakes
Received: 21 June 2011 / Accepted: 26 January 2012 / Published online: 10 February 2012 # Springer Science+Business Media B.V. 2012
Abstract We examined foraging adaptations and diet among dominant fishes within two species-rich riffle habitats in Thailand headwater rivers during the early and late portions of the dry season. All species exhibited diel temporal variations in feeding activity. Some species fed principally during daylight, while others fed mainly during darkness. Feeding patterns within species were generally spatially and temporally consistent. All seven fishes exploited the same benthic prey, but their foraging activities were related to spatially distinct water velocities. Diets overlapped with Ephemeroptera and Trichoptera the quantitatively most important prey. Ostracods, while not a large contributor to diet biomass, were numerically important in the diet of Homaloptera smithi. Trophic diversification through diel temporal feeding patterns and microhabitat separation by water velocity are major tactics in maintaining high diversity in riffle assemblages in Thai headwater rivers.
P. Nithirojpakdee (*) : F. W. H. Beamish Environmental Science, Faculty of Science, Burapha University, Bangsaen, Chonburi 20131, Thailand e-mail:
[email protected] D. L. G. Noakes Fish and Wildlife Department and Oregon Hatchery Research Center, Oregon State University, Corvallis, OR 97331-3803, USA
Keywords Benthic fishes . Diet . Feeding . Resource sharing . Temporal and spatial tactics . SE Asia
Introduction Species packing is thought to be affected by three major resource dimensions, habitat, food and time (Pianka 1970; Schoener 1974), particularly the availability and quality of each, and by competitive or sharing mechanisms related to specific features of morphology, and physiology as well as behavioral tactics (Ross 1986; Piet 1998). Closely related species tend to segregate in relation to at least one major resource with the degree possibly related to intraspecific genetic variations (Castillo-Rivera et al. 1996; Mookerji et al. 2004). Thus, some species are adapted morphologically, for example mouth size, to feed on dissimilar components of a broad food base (Matthews et al. 1982). Food availability and its nutritional qualities are also subject to vary with species’ physiology (Pierce and Wissing 1974; Ogino 1980), morphology (Wikramanayake 1990; Wainwright and Richard 1995) and behavioral characteristics (Werner and Hall 1974; Scott et al. 2005). Greenfield et al. (1983) suggest differences in morphology, physiology and behavior may be particularly characteristic of a tropical, species-rich assemblage, thereby allowing for greater species packing potential. Additionally, competition among species sharing a similar habitat may be reduced through differences
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in diet, temporal differences in feeding and partial or full reductions in diet overlap (Page and Schemske 1978). The importance of competition in assemblage structure within any or all of the resource axes is characterized by uncertainty, even contradiction. A number of notable feeding studies have been conducted in tropical freshwaters (e.g. Gerking 1994; Lowe-McConnell 1987; Herder and Freyhof 2006), although few have emerged from Southeast Asia. The high diversity typical of tropical communities has been of interest, particularly the basis for this high diversity (Matthews 1998; Dudgeon 2000). Species diversity varies greatly among habitats and typically is higher in tropical than temperate freshwaters (Matthews 1998). Certainly the total number of species in tropical regions exceeds those in nearctic and palearctic regions, especially relative to areas or volumes of freshwater. Tropical freshwater species tend to have smaller total habitats or available quantities of water than do species from nearctic and palearctic regions (Vidthayanon et al. 1997; Scharpf 2011). With less water or habitat available it is reasonable to expect more competition or sharing among species for resources in tropical than other regions and that this should foster appropriate adaptations and tactics among tropical species. Related earlier studies examined morphological features associated with feeding among fishes sharing the same assemblage (Ward-Campbell et al. 2005) as well as those associated with feeding during ontogeny (Ward-Campbell and Beamish 2005). In the present study we examined foraging behaviour of seven species that co-exist in riffle habitats of two headwater rivers in eastern Thailand. We tested the following predictions:(1) Species exhibit diel temporal feeding patterns (2) Diel temporal feeding patterns differ among species (3) Diet composition varies among fish species (4) Species occupy different microhabitats within the same riffles. These predictions will allow us to refine our understanding of the mechanisms involved in competition or sharing for food resources in Thailand headwater rivers.
Material and methods We collected fish for the temporal feeding studies from a riffle region in each of Klong Pai Boon (KPB) and Klong Khruv Wai (KKW) rivers in southeastern Thailand, between latitudes 12o52′ 29.3″N and
Environ Biol Fish (2012) 95:227–236
12o53 ′02.4″N and longitudes 102 o06′ 0.08″E and 102o06′53.6″E (Fig. 1). Riffles, approximately 60 m long by 20 m in width, were located on road—accessible tributaries in sparsely to lightly settled areas where some subsistence to modest commercial agriculture occurred. Both riffles were of generally similar depth, without submerged objects such as wood and with little cover (15 electrofishing collections at each station made throughout the year between 2000 and 2009
Abundance
Abundance
KPB
KKW
Species
KPB
KKW
Akysis maculipinnis
S
Amblyceps foratum
A
S
Nandas nebulosus
S
S
A
Nemacheilus masyae
M
Channa gachua
M
S
A
Neolissochilus stracheyi
M
S
Clarias macrocephalus
S
S
Notopterus notopterus
S
S
Esomus metallicus
S
S
Ompok bimaculatus
S
S
Garra combodiensis
M
S
Osteochilus hasseli
S
S
Glyptothorax laosensis
M
S
Oxyeleotris marmorata
S
S
G. major
M
S
Pangio myersi
S
S S
G. platypgonoides
S
S
Parambassis siamensis
S
Hampala macrolepidota
S
S
Poropuntius deauratus
S
S
Hemibagus nemurus
A
S
Pristolepis fasciatus
S
S
Homaloptera confuzona
S
S
Pseudomystus siamensis
A
M
H. smithi
A
A
Rasbora paviei
M
M
Lepiocephalichthys hasselti
S
S
Schistura kohchangensis
A
A
Macrognathus circumcinctus
M
S
Sinohomaloptera kwangsiensis
S
A
Mastacembelus armatus
A
A
Tetradon cambodgensis
S
S
Monopterus albus
S
S
Trichopsis vittatus
M
S
Mystacoleucus marginatus
M
S
Xenentodon cancilla
S
S
in the stomach. Weight of dietary items was estimated by multiplying their fractional point value by total stomach contents. Multivariate permutation analyses of variance (PERMANOVA) using vegan (Oksanen et al. 2010; Oksanen 2011) were used to compare diet composition among species (A. foratum, H. smithi, M. armatus, P. siamensis and S. kohchangensis), stations and seasons. For all multivariate analyses (three factor, one way and univariate), diet category weights were transformed by taking the 4th root of log (x+1) to reduce the influence of diet items of high value and the Gower distance resemblance matrix was used to account for skewed data with many zero entries (Cannicci et al. 2007). Miscellaneous or unidentified components of the diet were excluded from all comparisons of diet composition. PERMANOVA of the full three factor model and one way PERMANOVA’s used only the species present at each station and season. One way PERMANOVAs were used to compare fish species diets within each station and within each season. Finally, to determine differences in diet composition within each
species, two factor PERMANOVAs were done. In all cases, significance was determined if p
