Journal of Fish Biology (2014) doi:10.1111/jfb.12529, available online at wileyonlinelibrary.com
Trophic interactions between native and introduced fish species in a littoral fish community M. Monroy*†, A. Maceda-Veiga‡, N. Caiola§ and A. De Sostoa* *Department of Animal Biology and Biodiversity Research Institute (IRBio), University of Barcelona, E-08028, Barcelona, Spain, ‡Cardiff School of Biosciences, Cardiff University, Cardiff CF10 3AX, U.K. and §Aquatic Ecosystems, IRTA, Sant Carles de la Ràpita, Spain (Received 4 March 2014, Accepted 6 August 2014) The trophic interactions between 15 native and two introduced fish species, silverside Odontesthes bonariensis and rainbow trout Oncorhynchus mykiss, collected in a major fishery area at Lake Titicaca were explored by integrating traditional ecological knowledge and stable-isotope analyses (SIA). SIA suggested the existence of six trophic groups in this fish community based on 𝛿 13 C and 𝛿 15 N signatures. This was supported by ecological evidence illustrating marked spatial segregation between groups, but a similar trophic level for most of the native groups. Based on Bayesian ellipse analyses, niche overlap appeared to occur between small O. bonariensis (0⋅05 >0⋅05 >0⋅05 >0⋅05
7⋅77 ± 0⋅23 8⋅8 ± 1⋅53 8⋅48 ± 1⋅93 7⋅30 ± 0⋅81 7⋅40 ± 0⋅49
0⋅00 0⋅67 0⋅59 −0⋅23 −0⋅15
>0⋅05 >0⋅05 >0⋅05 >0⋅05 >0⋅05
8 134⋅12 65–159 −16⋅90 ± 0⋅88 −0⋅49 >0⋅05
7⋅94 ± 1⋅14
−0⋅01
>0⋅05
−0⋅50 >0⋅05 6⋅64 ± 0⋅37 −0⋅60 >0⋅05 5⋅87 ± 0⋅42 −0⋅68 0⋅05 6⋅41 ± 0⋅52 −0⋅39 0⋅05 >0⋅05 >0⋅05 0⋅05
4 62⋅60 60–65 −18⋅29 ± 0⋅27 7 134⋅27 112–163 −18⋅09 ± 1⋅08 10 125⋅40 84–167 −17⋅41 ± 0⋅84 10 134⋅92 115–148 −17⋅30 ± 0⋅83 9 76⋅30 59–85 −16⋅81 ± 0⋅48
3 52⋅33 48–60 6 42⋅16 39–46 9 135⋅66 95–162 26 158⋅00 40–422
−16⋅37 ± 0⋅17 −15⋅88 ± 0⋅42 −15⋅10 ± 0⋅48 −17⋅33 ± 1⋅51
0⋅20 −0⋅60 −0⋅29 −0⋅21 0⋅19
8 200⋅00 149–268 −18⋅98 ± 0⋅48 −0⋅16 >0⋅05 10⋅40 ± 0⋅61
*Note that this list includes two species removed from ellipse analyses due to the reduced sample size (n < 5).
and traditional ecological studies can give complementary information about studies of food web structure (Vander Zanden & Vadeboncoeur, 2002; Clarke et al., 2005; Quevedo et al., 2009). Additionally, this is the first time that ecological attributes of six native species are explored to investigate the differential effect of the introduction of O. bonariensis and O. mykiss on the native fish community. N I C H E PA RT I T I O N I N G O F T H E N AT I V E F I S H C O M M U N I T Y
As predicted, most of the native fish groups showed a similar trophic level with marked spatial segregation, possibly associated with a decrease in trophic competition. The pelagic native O. ispi was the only native fish group showing higher 𝛿 15 N values than the remaining native fish groups. This could be attributed to the occasional consumption of eggs by this fish species (Paca et al., 2002). An additional reason for the high 𝛿 15 N of O. ispi might be that the pelagic condition enables O. ispi to feed on prey items from food webs differing in baseline levels of 𝛿 15 N, which may lead to a higher 𝛿 15 N (Hobson, 1999; Vander Zanden & Rasmussen, 2001; Bearhop et al., 2004). Likewise, the large deviations observed in the 𝛿 13 C values of T. rivulatus, O. luteus and O. agassii could be associated with the consumption of prey from different feeding grounds. The current findings may be related to the fact that different morphotypes have
© 2014 The Fisheries Society of the British Isles, Journal of Fish Biology 2014, doi:10.1111/jfb.12529
10
M . M O N R O Y E T A L.
(a)
1 0·8 0·6 0·4 0·2 0
(b)
1
Proportion
0·8 0·6 0·4 0·2 0
pI
ou
Gr
(c)
p ou Gr
II
p ou Gr
III o Gr
up
IV
s ids od om hip p Am
ton
nk
la op
Zo
Ch
n iro
1 0·8 0·6 0·4 0·2 0 Zooplankton
Chironomids Source
Amphipods
Fig. 3. Density plot showing the confidence intervals (95, 75 and 50%) of the relative proportion of Lake Titicaca fish groups consumed by (a) Oncorhynchus mykiss, (b) Odontesthes bonariensis and (c) O. bonariensis
Trophic interactions between native and introduced fish species in a littoral fish community M. Monroy*†, A. Maceda-Veiga‡, N. Caiola§ and A. De Sostoa* *Department of Animal Biology and Biodiversity Research Institute (IRBio), University of Barcelona, E-08028, Barcelona, Spain, ‡Cardiff School of Biosciences, Cardiff University, Cardiff CF10 3AX, U.K. and §Aquatic Ecosystems, IRTA, Sant Carles de la Ràpita, Spain (Received 4 March 2014, Accepted 6 August 2014) The trophic interactions between 15 native and two introduced fish species, silverside Odontesthes bonariensis and rainbow trout Oncorhynchus mykiss, collected in a major fishery area at Lake Titicaca were explored by integrating traditional ecological knowledge and stable-isotope analyses (SIA). SIA suggested the existence of six trophic groups in this fish community based on 𝛿 13 C and 𝛿 15 N signatures. This was supported by ecological evidence illustrating marked spatial segregation between groups, but a similar trophic level for most of the native groups. Based on Bayesian ellipse analyses, niche overlap appeared to occur between small O. bonariensis (0⋅05 >0⋅05 >0⋅05 >0⋅05
7⋅77 ± 0⋅23 8⋅8 ± 1⋅53 8⋅48 ± 1⋅93 7⋅30 ± 0⋅81 7⋅40 ± 0⋅49
0⋅00 0⋅67 0⋅59 −0⋅23 −0⋅15
>0⋅05 >0⋅05 >0⋅05 >0⋅05 >0⋅05
8 134⋅12 65–159 −16⋅90 ± 0⋅88 −0⋅49 >0⋅05
7⋅94 ± 1⋅14
−0⋅01
>0⋅05
−0⋅50 >0⋅05 6⋅64 ± 0⋅37 −0⋅60 >0⋅05 5⋅87 ± 0⋅42 −0⋅68 0⋅05 6⋅41 ± 0⋅52 −0⋅39 0⋅05 >0⋅05 >0⋅05 0⋅05
4 62⋅60 60–65 −18⋅29 ± 0⋅27 7 134⋅27 112–163 −18⋅09 ± 1⋅08 10 125⋅40 84–167 −17⋅41 ± 0⋅84 10 134⋅92 115–148 −17⋅30 ± 0⋅83 9 76⋅30 59–85 −16⋅81 ± 0⋅48
3 52⋅33 48–60 6 42⋅16 39–46 9 135⋅66 95–162 26 158⋅00 40–422
−16⋅37 ± 0⋅17 −15⋅88 ± 0⋅42 −15⋅10 ± 0⋅48 −17⋅33 ± 1⋅51
0⋅20 −0⋅60 −0⋅29 −0⋅21 0⋅19
8 200⋅00 149–268 −18⋅98 ± 0⋅48 −0⋅16 >0⋅05 10⋅40 ± 0⋅61
*Note that this list includes two species removed from ellipse analyses due to the reduced sample size (n < 5).
and traditional ecological studies can give complementary information about studies of food web structure (Vander Zanden & Vadeboncoeur, 2002; Clarke et al., 2005; Quevedo et al., 2009). Additionally, this is the first time that ecological attributes of six native species are explored to investigate the differential effect of the introduction of O. bonariensis and O. mykiss on the native fish community. N I C H E PA RT I T I O N I N G O F T H E N AT I V E F I S H C O M M U N I T Y
As predicted, most of the native fish groups showed a similar trophic level with marked spatial segregation, possibly associated with a decrease in trophic competition. The pelagic native O. ispi was the only native fish group showing higher 𝛿 15 N values than the remaining native fish groups. This could be attributed to the occasional consumption of eggs by this fish species (Paca et al., 2002). An additional reason for the high 𝛿 15 N of O. ispi might be that the pelagic condition enables O. ispi to feed on prey items from food webs differing in baseline levels of 𝛿 15 N, which may lead to a higher 𝛿 15 N (Hobson, 1999; Vander Zanden & Rasmussen, 2001; Bearhop et al., 2004). Likewise, the large deviations observed in the 𝛿 13 C values of T. rivulatus, O. luteus and O. agassii could be associated with the consumption of prey from different feeding grounds. The current findings may be related to the fact that different morphotypes have
© 2014 The Fisheries Society of the British Isles, Journal of Fish Biology 2014, doi:10.1111/jfb.12529
10
M . M O N R O Y E T A L.
(a)
1 0·8 0·6 0·4 0·2 0
(b)
1
Proportion
0·8 0·6 0·4 0·2 0
pI
ou
Gr
(c)
p ou Gr
II
p ou Gr
III o Gr
up
IV
s ids od om hip p Am
ton
nk
la op
Zo
Ch
n iro
1 0·8 0·6 0·4 0·2 0 Zooplankton
Chironomids Source
Amphipods
Fig. 3. Density plot showing the confidence intervals (95, 75 and 50%) of the relative proportion of Lake Titicaca fish groups consumed by (a) Oncorhynchus mykiss, (b) Odontesthes bonariensis and (c) O. bonariensis
