Pipefish are representatives of ichthyofauna from vegetated habitats in coastal and estuarine areas (Howard & Koehn 1985; Kuiter 2000). These are ideal habitats for feeding, reproduction, protection against predators and wintering (Teixeira & Musick 1995). Decaying algae and dead seagrass are known to serve as a shelter and refuge, and even as means of transportation to shallower or deeper waters (Teixeira & Musick 1995).
Lake Bafa is an alluvial lake located at the southeastern end of the Aegean region and connected to the Greater Meander delta (Turgutcan 1957). The lake is fed by the Meander River and therefore harbors a wide variety of fish species, thus representing a large ground for research on ichthyofauna. Changes in the populations of diadromous and potamodromous fish species are closely associated with the connection between lakes and rivers (Sarı et al. 1999). Research on fish species in Lake Bafa dates back 30 years and so far 20 species have been identified in the lake (Kasparek 1988; Balık & Ustaoglu 1989; Kuru et al. 2001). In addition to economic species, species from the Syngnathus genus occur in the lake (Sarı et al. 1999; Kuru et al. 2001; Gurkan & Innal 2018). In Europe, research on feeding strategies, especially of
The study carried out by Franzoi et al. (1993) involved feeding habits of two Syngnathus species in an estuarine system of the Mediterranean Sea (Po River delta). Research by Vizzini & Mazzola (2004) on the trophic structure of pipefish species from the western Mediterranean coast is important, because the authors addressed the issue in detail. The most recent study, according to our review of the relevant literature, determined the feeding model of
This is an important study, because it is the first time the trophic ecology of two congeneric pipefish species occurring in alluvial Lake Bafa (Aegean region, Turkey) has been determined. The study investigates changes in prey group choices of both Syngnathus species with respect to two seasons (autumn and spring), length groups, sex and morphological differences in the mouth apparatus.
Lake Bafa is a natural barrier lake located in the southeastern region of the Greater Meander River delta and has an indented shoreline. Pipefish samples were collected seasonally, from November 2014 to March 2016, by seining in the coastal area of the Kapıkırı region (between 37°30′N–27°31′E and 37°29′N–27°31′E), the maximum depth of which is 1–1.5 m (Fig. 1). The potential effect of the mesh opening was ignored. Ethics committee regulations were followed when fish species were caught. A total of 205 fish individuals were caught (
Figure 1
Fish samples

The tubular gastrointestinal system of pipefish is not fully developed. For the purpose of examining digested food particles, the anterior of the gastrointestinal tube was defined as the gut. The guts were dissected and removed. The gut content analysis was performed on 149 samples with full guts. The dissected guts were kept in 4% formalin solution. Empty and full guts were examined under a binocular microscope. Prey items found in full guts were identified according to different groups. Food particles were counted and weighed with a sensitivity of 0.0001 g. Dominant prey groups were determined in the gut contents of both fish species.
Fish with empty and full guts were determined. The feeding activity was described using the fullness index FI (Hureau 1969). The fullness index was calculated using the following formula: FI = 100*(Gut W) *(W)−1, where Gut W is the gut content weight and W is the fish weight.
Frequency of gut contents (F%), numerical occurrence (N%), weight percentage (W%), the index of relative importance (IRI) and the percent index of relative importance (IRI %) with respect to length groups and two seasons were separately calculated in accordance with Liao & Larscheid (2001). The t-test was used both to determine the differences in the gut contents with respect to length groups and seasons as well as the correlation and regression relationships between the total length and mouth width (Sokal, Rohlf 1969). One-way ANOVA was performed using the Statistica software.
A total of 76 samples (44 females, 25 males, 7 immatures) were collected in the study period, i.e. in spring and autumn. The total length of the samples varied from 55 mm to 130 mm, with Length Group II containing the largest number of samples (75%). The gut fullness ratio in the samples was 68.42% and it was higher in female samples (75%) than in male samples.
Eight major prey groups were identified in
Stomach contents in
Prey items | F% | N% | W% | IRI% |
---|---|---|---|---|
Copepods | ||||
| 51.06 | 64.71 | 1.26 | 10.99 |
Other cyclopoids | 4.26 | 1.76 | 0.20 | 0.03 |
Ostracods | 10.64 | 0.79 | 0.16 | 0.03 |
Amphipods | 68.09 | 18.44 | 0.81 | 4.28 |
Amphipod pieces | 10.64 | 0.00 | 0.00 | 0.00 |
Diptera | ||||
Chironomidae larvae | 4.26 | 0.48 | 93.67 | 1.31 |
Fish larvae ( | 2.13 | 0.32 | 0.74 | 0.01 |
Unknown eggs | 2.13 | 13.51 | 3.16 | 0.12 |
Total prey number | 629 | |||
Number of full stomachs | 52 |
Note: F% – percentage frequency; N% – percentage of prey number; W% – percentage dry weight; IRI% – percentage relative importance index.
Food composition in
Prey items | Fish length groups | |||||
---|---|---|---|---|---|---|
< 60 mm | 60–100 mm | 100 mm > | ||||
F% | IRI% | F% | IRI% | F% | IRI% | |
Copepods | ||||||
| 0.00 | 0.00 | 56.10 | 0.49 | 7.37 | 28.99 |
Other cyclopoids | 0.00 | 0.00 | 4.88 | 0.88 | 0.00 | 0.00 |
Ostracods | 0.00 | 0.00 | 14.63 | 1.66 | 0.00 | 0.00 |
Amphipods | 0.00 | 0.00 | 56.10 | 82.12 | 75.00 | 57.56 |
Amphipod pieces | 0.00 | 0.00 | 36.59 | 0.00 | 0.00 | 0.00 |
Diptera | ||||||
Chironomidae larvae | 0.00 | 0.00 | 4.88 | 7.31 | 0.00 | 0.00 |
Fish larvae ( | 0.00 | 0.00 | 2.44 | 0.06 | 8.33 | 0.61 |
Unknown eggs | 0.00 | 0.00 | 2.44 | 0.95 | 8.33 | 12.84 |
Figure 2
Relationship between the total length and the stomach fullness index in

According to Table 2, guts in the samples of Length Group I were empty, while the samples in Length Group II contained eight prey groups. In these medium-size samples, amphipods and
Food composition in
Prey items | Autumn | Spring | ||
---|---|---|---|---|
F% | IRI% | F% | IRI% | |
Copepods | ||||
| 0.00 | 0.00 | 96.00 | 97.55 |
Other cyclopoids | 6.67 | 3.22 | 0.00 | 0.00 |
Ostracods | 16.67 | 3.63 | 0.00 | 0.00 |
Amphipods | 53.33 | 76.81 | 64.00 | 2.17 |
Amphipod pieces | 43.33 | 0.00 | 0.00 | 0.00 |
Diptera | ||||
Chironomidae larvae | 6.67 | 16.14 | 0.00 | 0.00 |
Fish larvae ( | 3.33 | 0.18 | 4.00 | 0.002 |
Unknown eggs | 0.00 | 0.00 | 8.00 | 0.28 |
Only six prey groups were favored by individuals caught in autumn. Amphipods were the most dominant and important prey group in autumn, followed by chironomid larvae, which are aquatic insects. Fish larvae were also preferred, albeit at a low level. Four prey groups were consumed in spring and
A total of 129 samples (69 females, 30 males, 30 immatures) were collected during the study period. The total length values of the samples ranged from 55 mm to 125 mm and Length Group II contained the largest number of samples (57.5%). The gut fullness ratio for the species was 75.1% and it was higher in female samples (70%) than in male samples (63.76%). Of the 16 prey groups identified based on the feeding activity of
Stomach contents in
Prey items | F% | N% | W% | IRI % |
---|---|---|---|---|
Algae | ||||
Diatom ( | 1.54 | 0.15 | 0.00 | 0.004 |
Brown algae pieces | 1.53 | 0.00 | 0.00 | 0.00 |
Copepods | ||||
| 44.62 | 51.35 | 1.58 | 42.37 |
Other Calanoids | 1.54 | 0.30 | 0.002 | 0.009 |
| 1.54 | 0.15 | 0.009 | 0.004 |
Other cyclopoids | 10.77 | 3.61 | 0.64 | 0.82 |
Harpacticoids | 1.54 | 0.15 | 0.0002 | 0.004 |
Ostracods | 4.61 | 0.45 | 0.24 | 0.06 |
Mysids | 1.54 | 0.15 | 0.09 | 0.007 |
Amphipods | 66.15 | 42.62 | 2.90 | 54.04 |
Amphipod pieces | 36.92 | 0.00 | 0.00 | 0.00 |
Gastropods | 3.08 | 0.15 | 0.01 | 0.009 |
Diptera | ||||
Chironomidae larvae | 1.54 | 0.15 | 46.96 | 1.29 |
Other Diptera larvae | 1.54 | 0.15 | 46.69 | 1.29 |
Fish larvae ( | 3.08 | 0.30 | 4.35 | 0.08 |
Fish scales | 1.54 | 0.15 | 0.00 | 0.04 |
Total prey number | 664 | |||
Number of full stomachs | 65 |
The highest value of the gut fullness index was 17.9 and was determined in Length Group II in spring, while the lowest value was 0.22 and was determined in Length Group III (Table 2, Fig. 3).
Figure 3
Relationship between the total length and the stomach fullness index in

According to Table 5, samples in Length Group I contained only one type of prey group (
Food composition in
Prey Items | Length groups | |||||
---|---|---|---|---|---|---|
< 60 mm | 60–100 mm | 100 mm > | ||||
F% | IRI% | F% | IRI% | F% | IRI% | |
Algae | ||||||
Diatom ( | 0.00 | 0.00 | 2.13 | 0.004 | 4.00 | 0.00 |
Brown algae pieces | 0.00 | 0.00 | 0.00 | 0.00 | 4.00 | 0.00 |
Copepods | ||||||
| 100.00 | 100.00 | 51.06 | 76.57 | 16.00 | 3.23 |
Other Calanoids | 0.00 | 0.00 | 2.13 | 0.01 | 0.00 | 0.00 |
| 0.00 | 0.00 | 2.13 | 0.004 | 0.00 | 0.00 |
Other Cyclopoids | 0.00 | 0.00 | 14.89 | 0.72 | 4.00 | 0.02 |
Harpacticoids | 0.00 | 0.00 | 2.13 | 0.004 | 0.00 | 0.00 |
Ostracods | 0.00 | 0.00 | 4.26 | 0.02 | 4.00 | 0.02 |
Mysids | 0.00 | 0.00 | 0.00 | 0.00 | 4.00 | 0.02 |
Amphipods | 0.00 | 0.00 | 59.57 | 22.47 | 60.00 | 96.65 |
Amphipod pieces | 0.00 | 0.00 | 31.91 | 0.00 | 40.00 | 0.00 |
Gastropods | 0.00 | 0.00 | 2.13 | 0.04 | 0.00 | 0.00 |
Diptera | ||||||
Chironomidae larvae | 0.00 | 0.00 | 0.00 | 0.00 | 4.00 | 0.03 |
Other Diptera larvae | 0.00 | 0.00 | 2.13 | 0.18 | 0.00 | 0.00 |
Fish larvae ( | 0.00 | 0.00 | 2.13 | 0.01 | 4.00 | 0.02 |
Fish scales | 0.00 | 0.00 | 2.13 | 0.004 | 0.00 | 0.00 |
Table 6 shows the prey groups identified in the
Prey groups consumed by
Prey items | Autumn | Spring | ||
---|---|---|---|---|
F% | IRI% | F% | IRI% | |
Algae | ||||
Diatom ( | 3.13 | 0.22 | 0.00 | 0.00 |
Brown algae pieces | 0.00 | 0.00 | 1.35 | 0.00 |
Copepods | ||||
| 3.13 | 0.22 | 37.84 | 93.19 |
Other calanoids | 3.13 | 0.44 | 0.00 | 0.00 |
| 3.13 | 0.23 | 0.00 | 0.00 |
Other cyclopoids | 3.13 | 0.23 | 8.11 | 0.0002 |
Harpacticoids | 0.00 | 0.00 | 1.35 | 0.0002 |
Ostracods | 9.38 | 1.98 | 0.00 | 0.00 |
Mysids | 3.13 | 0.22 | 0.00 | 0.00 |
Amphipods | 50.00 | 85.18 | 36.49 | 6.75 |
Amphipod pieces | 43.75 | 0.00 | 13.52 | 0.00 |
Gastropods | 3.13 | 0.23 | 0.00 | 0.00 |
Diptera | ||||
Chironomidae larvae | 3.13 | 9.18 | 0.00 | 0.00 |
Other Diptera larvae | 0.00 | 0.00 | 1.35 | 0.06 |
Fish larvae ( | 6.25 | 1.42 | 0.00 | 0.00 |
Fish scales | 3.13 | 0.22 | 0.00 | 0.00 |
Thirteen prey groups dominated in the samples in autumn. Amphipods and amphipod pieces were the most dominant and important prey group in autumn. In addition, Ostracods, Chironomidae larvae and fish larvae were preferred, albeit at a low level. The collected fish individuals consumed seven prey groups in spring, and
Figure 4
Relationships between the total length and the mouth width in pipefish species

The mouth width (MW) of
Figure 5
Relationship between the total length and the total weight of ingested food in pipefish species

Figure 5 shows the regression relationship between the total length (TL) and the food weight for both species. The figure reveals that feeding in the captured individuals of
Pipefish species are bony fish with high trophic specialization, distinguished from other demersal fish species by distinct mouth morphology and feeding habits (Kendrick & Hyndes 2005). The main food items of pipefish are usually groups of small crustaceans (Howard & Koehn 1985; Tipton & Bell 1988; Franzoi et al. 1993; Lyons & Dunne 2004; Taskavak et al. 2010). The mouth apparatus of pipefish has a structural effect on prey capture (De Lussanet & Muller 2007). In this study, the length distribution of
The food of
In this study, the captured individuals of
The number of studies investigating the food consumption and dominant prey groups in
Considering the seasons, amphipods and chironomid larvae were the most dominant and important prey groups for sampled
The results of the study showed that zooplankton was the main prey group in the alluvial lake environment, and the differences in feeding habits of the two species were attributable to the differences in their mouth apparatus. However, the effect of pipefish on the food ecology of the lake was not significant. On the other hand, maintaining the existing aquatic vegetation in the lake will help in the survival of the fish species and allow more detailed studies.
Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Food composition in S.abaster stomachs in two seasons
Prey items | Autumn | Spring | ||
---|---|---|---|---|
F% | IRI% | F% | IRI% | |
Copepods | ||||
|
0.00 | 0.00 | 96.00 | 97.55 |
Other cyclopoids | 6.67 | 3.22 | 0.00 | 0.00 |
Ostracods | 16.67 | 3.63 | 0.00 | 0.00 |
Amphipods | 53.33 | 76.81 | 64.00 | 2.17 |
Amphipod pieces | 43.33 | 0.00 | 0.00 | 0.00 |
Diptera | ||||
Chironomidae larvae | 6.67 | 16.14 | 0.00 | 0.00 |
Fish larvae ( |
3.33 | 0.18 | 4.00 | 0.002 |
Unknown eggs | 0.00 | 0.00 | 8.00 | 0.28 |
Food composition in S. abaster size groups
Prey items | Fish length groups | |||||
---|---|---|---|---|---|---|
< 60 mm | 60–100 mm | 100 mm > | ||||
F% | IRI% | F% | IRI% | F% | IRI% | |
Copepods | ||||||
|
0.00 | 0.00 | 56.10 | 0.49 | 7.37 | 28.99 |
Other cyclopoids | 0.00 | 0.00 | 4.88 | 0.88 | 0.00 | 0.00 |
Ostracods | 0.00 | 0.00 | 14.63 | 1.66 | 0.00 | 0.00 |
Amphipods | 0.00 | 0.00 | 56.10 | 82.12 | 75.00 | 57.56 |
Amphipod pieces | 0.00 | 0.00 | 36.59 | 0.00 | 0.00 | 0.00 |
Diptera | ||||||
Chironomidae larvae | 0.00 | 0.00 | 4.88 | 7.31 | 0.00 | 0.00 |
Fish larvae ( |
0.00 | 0.00 | 2.44 | 0.06 | 8.33 | 0.61 |
Unknown eggs | 0.00 | 0.00 | 2.44 | 0.95 | 8.33 | 12.84 |
Food composition in S. acus size groups
Prey Items | Length groups | |||||
---|---|---|---|---|---|---|
< 60 mm | 60–100 mm | 100 mm > | ||||
F% | IRI% | F% | IRI% | F% | IRI% | |
Algae | ||||||
Diatom ( |
0.00 | 0.00 | 2.13 | 0.004 | 4.00 | 0.00 |
Brown algae pieces | 0.00 | 0.00 | 0.00 | 0.00 | 4.00 | 0.00 |
Copepods | ||||||
|
100.00 | 100.00 | 51.06 | 76.57 | 16.00 | 3.23 |
Other Calanoids | 0.00 | 0.00 | 2.13 | 0.01 | 0.00 | 0.00 |
|
0.00 | 0.00 | 2.13 | 0.004 | 0.00 | 0.00 |
Other Cyclopoids | 0.00 | 0.00 | 14.89 | 0.72 | 4.00 | 0.02 |
Harpacticoids | 0.00 | 0.00 | 2.13 | 0.004 | 0.00 | 0.00 |
Ostracods | 0.00 | 0.00 | 4.26 | 0.02 | 4.00 | 0.02 |
Mysids | 0.00 | 0.00 | 0.00 | 0.00 | 4.00 | 0.02 |
Amphipods | 0.00 | 0.00 | 59.57 | 22.47 | 60.00 | 96.65 |
Amphipod pieces | 0.00 | 0.00 | 31.91 | 0.00 | 40.00 | 0.00 |
Gastropods | 0.00 | 0.00 | 2.13 | 0.04 | 0.00 | 0.00 |
Diptera | ||||||
Chironomidae larvae | 0.00 | 0.00 | 0.00 | 0.00 | 4.00 | 0.03 |
Other Diptera larvae | 0.00 | 0.00 | 2.13 | 0.18 | 0.00 | 0.00 |
Fish larvae ( |
0.00 | 0.00 | 2.13 | 0.01 | 4.00 | 0.02 |
Fish scales | 0.00 | 0.00 | 2.13 | 0.004 | 0.00 | 0.00 |
Prey groups consumed by S. acus during two seasons
Prey items | Autumn | Spring | ||
---|---|---|---|---|
F% | IRI% | F% | IRI% | |
Algae | ||||
Diatom ( |
3.13 | 0.22 | 0.00 | 0.00 |
Brown algae pieces | 0.00 | 0.00 | 1.35 | 0.00 |
Copepods | ||||
|
3.13 | 0.22 | 37.84 | 93.19 |
Other calanoids | 3.13 | 0.44 | 0.00 | 0.00 |
|
3.13 | 0.23 | 0.00 | 0.00 |
Other cyclopoids | 3.13 | 0.23 | 8.11 | 0.0002 |
Harpacticoids | 0.00 | 0.00 | 1.35 | 0.0002 |
Ostracods | 9.38 | 1.98 | 0.00 | 0.00 |
Mysids | 3.13 | 0.22 | 0.00 | 0.00 |
Amphipods | 50.00 | 85.18 | 36.49 | 6.75 |
Amphipod pieces | 43.75 | 0.00 | 13.52 | 0.00 |
Gastropods | 3.13 | 0.23 | 0.00 | 0.00 |
Diptera | ||||
Chironomidae larvae | 3.13 | 9.18 | 0.00 | 0.00 |
Other Diptera larvae | 0.00 | 0.00 | 1.35 | 0.06 |
Fish larvae ( |
6.25 | 1.42 | 0.00 | 0.00 |
Fish scales | 3.13 | 0.22 | 0.00 | 0.00 |
Stomach contents in Syngnathus acus
Prey items | F% | N% | W% | IRI % |
---|---|---|---|---|
Algae | ||||
Diatom ( |
1.54 | 0.15 | 0.00 | 0.004 |
Brown algae pieces | 1.53 | 0.00 | 0.00 | 0.00 |
Copepods | ||||
|
44.62 | 51.35 | 1.58 | 42.37 |
Other Calanoids | 1.54 | 0.30 | 0.002 | 0.009 |
|
1.54 | 0.15 | 0.009 | 0.004 |
Other cyclopoids | 10.77 | 3.61 | 0.64 | 0.82 |
Harpacticoids | 1.54 | 0.15 | 0.0002 | 0.004 |
Ostracods | 4.61 | 0.45 | 0.24 | 0.06 |
Mysids | 1.54 | 0.15 | 0.09 | 0.007 |
Amphipods | 66.15 | 42.62 | 2.90 | 54.04 |
Amphipod pieces | 36.92 | 0.00 | 0.00 | 0.00 |
Gastropods | 3.08 | 0.15 | 0.01 | 0.009 |
Diptera | ||||
Chironomidae larvae | 1.54 | 0.15 | 46.96 | 1.29 |
Other Diptera larvae | 1.54 | 0.15 | 46.69 | 1.29 |
Fish larvae ( |
3.08 | 0.30 | 4.35 | 0.08 |
Fish scales | 1.54 | 0.15 | 0.00 | 0.04 |
Total prey number | 664 | |||
Number of full stomachs | 65 |
Stomach contents in Syngnathus abaster
Prey items | F% | N% | W% | IRI% |
---|---|---|---|---|
Copepods | ||||
|
51.06 | 64.71 | 1.26 | 10.99 |
Other cyclopoids | 4.26 | 1.76 | 0.20 | 0.03 |
Ostracods | 10.64 | 0.79 | 0.16 | 0.03 |
Amphipods | 68.09 | 18.44 | 0.81 | 4.28 |
Amphipod pieces | 10.64 | 0.00 | 0.00 | 0.00 |
Diptera | ||||
Chironomidae larvae | 4.26 | 0.48 | 93.67 | 1.31 |
Fish larvae ( |
2.13 | 0.32 | 0.74 | 0.01 |
Unknown eggs | 2.13 | 13.51 | 3.16 | 0.12 |
Total prey number | 629 | |||
Number of full stomachs | 52 |
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