Preliminary results on the feeding and gut content of Flaccisagitta enflata in coastal areas of İskenderun Bay (northeastern Mediterranean Sea)

KSÜ Tarım ve Doğa Derg 21(5):765-771, 2018 KSU J. Agric Nat 21(5):765-771, 2018 Preliminary Results on the Feeding and Gut Content of Flaccisagitta enflata in Coastal Areas of İskenderun Bay (Northeastern Mediterranean Sea) Tuba TERBIYIK KURT Çukurova Üniversitesi, Su Ürünleri Fakültesi, Temel Bilimler Bölümü, Adana : ABSTRACT In this study, it was aimed to characterize the feeding and diet composition of the most common pelagic chaetognath Flaccisagitta enflata. Zooplankton samples were collected using a WP-2 zooplankton net (200 µm) at three stations in the İskenderun Bay in October 2016, December 2016 and March 2017. F. enflata was the most abundant chaetognath in all samples and its proportion varied from 42 to 94%. Younger stages (I and II) dominated the population of F. enflata. In total, 1663 specimens were examined, but only 185 contained prey in their guts. The total food-containing ratio and the number of prey items for this chaetognath species were 11% and 0.1, respectively. These values varied for different maturity stages. Most food items were unidentified due to digestion. Copepods were the main food resource (36.8%) for the species. Cannibalism was also observed. This study is the first to describe F. enflata feeding behaviour in the coastal area of İskenderun Bay. The preliminary results show that the feeding ratios were within the ranges reported for other regions in the eastern Mediterranean Sea. DOI :10.18016/ksudobil.406362 Article History Received : 15.03.2018 Accepted : 16.04. 2018 Keywords Flaccisagitta enflata, feeding, FCR, NPC, İskenderun Bay Research Article İskenderun Körfezi (Kuzeydoğu Akdeniz) Kıyısal Sularında Flaccisagitta enflata (Grassi, 1881)’nın Beslenmesi ve Bağırsak İçeriği Üzerine İlk Gözlemler ÖZET Mevcut çalışmada, en yaygın pelajik ketognat olan Flaccisagitta enflata’nın beslenmesi ve besin kompozisyonu karakterize edilmeye çalışılmıştır. Zooplankton örnekleri, İskenderun Körfezi’nde Ekim ve Aralık 2016, Mart, 2017 periyotlarında 3 istasyonda WP-2 zooplankton kepçesi (200 µm) ile toplanmıştır. Ketognatlar içinde, F. enflata, tüm periyotlarda baskın tür olarak gözlenmiş olup, oranı %42–94 arasında değişim göstermiştir. Erken olgunluk aşamaları (I ve II) F. enflata populasyonunda baskın olarak gözlenmiştir. Toplam 1663 birey incelenmiş olup, bunlardan sadece 185 bireyin bağırsağında besine rastlanmıştır. Bu tür için toplam besin içerme oranı (FCR) ve ketognat başına düşen besin miktarı (NPC) sırasıyla %11 ve 0.1 olarak bulunmuştur. Bu değerler olgunluk aşamalarına göre farklılık göstermiştir. Çoğu besin sindirilmiş olduğundan dolayı tanımlanamamıştır. Tanımlanan besin canlılar arasında kopepodlar ana besin kaynağını oluşturmuştur (%36.8). Bununla birlikte kannibalizm’de gözlenmiştir. Bu çalışmada ilk kez İskenderun Körfezi’nin kıyısal alanında F. enflata’nın beslenmesi ile ilgili bilgiler elde edilmiş ve ilk gözlemler beslenme oranlarının Doğu Akdeniz’in diğer alanlarından elde edilen sonuçlar ile benzer olduğunu göstermiştir. Makale Tarihçesi Geliş Tarihi : 15.03.2018 Kabul Tarihi: 16.04.2018 Anahtar Kelimeler Flaccisagitta enflata, beslenme, FCR, NPC, İskenderun Körfezi Araştırma makalesi To cite : Terbıyık Kurt T 2018. İskenderun Körfezi (Kuzeydoğu Akdeniz) kıyısal sularında Flaccisagitta enflata (Grassi, 1881)’nın beslenmesi ve bağırsak içeriği üzerine ilk gözlemler. KSÜ Tarim ve Doğa Derg 21(3), 765-771, 2018. DOI:10.18016/ksudobil.406362 KSÜ Tarım ve Doğa Derg 21(5):765-771, 2018 Araştırma Makalesi/Research Article INTRODUCTION species among chaetognaths in Mediterranean coastal ecosystems (Kehayias et al., 1999b). The aim of this study was to provide new information about the ecological role of the chaetognath F. enflata as secondary consumers in the productive coastal areas of İskenderun Bay (northeastern Levantine Basin) by studying their diet and feeding ratio. Thus, the present study contributes to better understanding of the food web interaction in the pelagic ecosystem in order to provide basic information for future studies in the basin. Chaetognaths are carnivorous organisms living in all marine and ocean habitats (Bone et al., 1991). Taking into consideration of their biomass and global distribution, this organism tends to be one of the most important groups in their ecosystems. The chaetognath biomass can be as high as 30% of the total biomass of copepods in all world oceans (Reeve, 1970). The feeding is the main route for transferring energy and matter between communities from lower to higher trophic levels (Bamstedt et al., 2000). Chaetognaths are dominant zooplanktonic predators and generally affect the population of their food organisms in environmental conditions with low organic production (Kimmerer, 1984; Oresland, 1990), such as the Eastern Mediterranean Sea. They feed mainly on copepods (Oresland, 1987), however, they can occasionally can consume a wide variety of other zooplankters (Feigenbaum, 1991). This group may cause problems in fish breeding regions due to consuming fish larvae and eggs as food. Another factor that makes these organisms important is that they contribute significantly to the matter and energy cycle by creating an important link between larger-sized predators, including commercial fish species, and smaller-sized animal organisms (Reeve, 1970; Nagasawa and Marumo, 1981). MATERIALS and METHODS Study area İskenderun Bay located in the north-eastern region of the eastern Mediterranean Sea covers approximately 2275 km2 (Figure 1). The average depth of the Bay is around 70 m (Avşar, 1999) and it is known to have the largest continental shelf area after the Nile Delta in the eastern Mediterranean Sea. The Bay is affected by deep currents and wind movements because it has a wide opening connecting to open sea waters (İyiduvar, 1986). The largest stream that flows into the Iskenderun Bay is the Ceyhan River with an average flow rate of 180 m3/ sec. There is clear seasonal cycling in the İskenderun coastal area. The temperature drops to approximately 17.5 °C in the winter-spring periods, and begins to rise after spring, reaching the highest levels in the summer (29.23 °C). Moreover, the salinity values fluctuate between 36.96 and 41.12‰ due to fresh water and terrestrial inputs (Terbıyık Kurt and Polat, 2015). Various studies on the distribution of chaetognath species have been conducted in world oceans (Itoh et al., 2006; Kosobokova and Hopcroft, 2010; Coston-Clements et al., 2009; Pierrot-Bults and Nair, 2010; Noblezada and Campos, 2008), especially in the Mediterranean Sea (Andreu, 1992; Kehayias et al. 1994, 1996; Duro and Saiz, 2000; Kehayias 2003, 2004; Batistic et al., 2003; Terbıyık et al., 2007; Kehayias and Ntakou, 2008; Kehayias and Kourouvakalis, 2010). Besides studies on chaetognath distribution, the feeding and predation impact of chaetognaths on their prey has been the subject of several inadequate studies in the Mediterranean Sea (Kehayias et al., 1996; Du (...truncated)