The Kais kingfish,
Freyhof (2014a) evaluated this species as the Least Concern on the Red List of the IUCN based on the following reasons. The species is confined to the areas that are characterised by flowing water. Individuals of this species usually move from this moving water region to canals and other aquatic habitats for feeding. It is widespread in the Tigris-Euphrates Rivers basin, representing several separate populations.
The Tigris kingfish,
Freyhof (2014b) evaluated this species as the Least Concern in the Red List of the IUCN based on the following reasons. This species is common, usually very abundant, and not eligible for a threat category.
Otoliths are heavy crystalline formations located in the inner ear of fish, which are created by the deposition of concentric layers of calcium carbonate in the structure of aragonite and the protein otoline and have annual growth rings. There are three pairs of otoliths in teleost: sagittae, lapilli, and asterisci (Campana & Casselman 1993, Green et al. 2009). The sagitta is frequently the largest otolith in most fishes (Tuset et al. 2008); nevertheless, the asteriscus is bigger in ostariophysian fishes (Harvey et al. 2000, Campana & Casselman 1993). Sagitta and asterisci otoliths vary in shape among species, while the shape of lapilli is more consistent (Campana 2004). The otoliths are considered chemically inert configurations because, after deposition of the layers, they remain meta- biologically inactive during the individual’s life (Green et al. 2009). As valuable tools in taxonomy, the surface features of the otoliths can change during the growth of the individuals of the species and between different species of fish (de Assis et al. 2018). Regarding such features, a link was discovered between body size and otolith size (Altin & Ayyildiz 2017, Zan 2015). This biometric relationship is imperative in food investigations since otoliths are very resistant to processes of digestion, making it possible to recognise species and resolve prey size, which in turn permits improved scrutiny of predator-prey associations and feeding habitats of piscivorous species (Granadeiro & Silva 2000, Jobling & Breiby 1986). The biometric link could as well benefit from the resumption of paleontological research of modern bony fish, as otoliths are well-conserved configurations in fossils of marine species (Reichenbacher et al. 2007). The link between fish length and otolith size has been effectively applied in numerous studies for marine and freshwater fish species (Zan et al. 2015, Viva et al. 2015, Yilmaz et al. 2015, Jawad et al. 2017, Saygin et al. 2020, Jawad & Adams 2021).
With the significance and the practicability of these biometric relationships, the present work intended to confirm the presence of links between the biometric measurements of the asteriscus (length, width, mass) and the body size (total, standard, and fork length) of the Tigris kingfish,
The province of Şirnak is one of the important regions of Türkiye, located in southeastern Anatolia. It has a population of 403,607 (Baz 2016) and is rich in mountains in the west and the south. Still, the more significant part of the region comprises elevations created by the many rivers that cross it. The chief of these rivers is the Tigris River and its tributaries, the Hezil, the Kizilsu, and the Çağlayan (Baz 2016). The members of the family Cyprinidae dominate the freshwater system of Türkiye (ÇiÇek et al. 2020), and the two members of the genus
Map showing the location of sampling
Asteriscus otolith of
The biostatistics of the otolith biometric features are shown in Table 1. For
Data analysis of
Parameter/Species | Range | Mean (± SD) | Equation | R2 |
---|---|---|---|---|
Otolith length (mm) | 8.75 – 11.35 | 10.05 (1.23) | OL = 6 + 78.2 TL | 0.4330 |
OL = 180 + 81.0 SL | 0.3406 | |||
OL = 33 + 87.7 FL | 0.3963 | |||
Otolith width (mm) | 8.01 – 10.35 | 9.18 (1.02) | OW = 328 + 43.6 TL | 0.4059 |
OW = 450 + 42.7 SL | 0.2861 | |||
OW = 329 + 50.0 FL | 0.3891 | |||
Otolith mass (g) | 8 – 24 | 16 (0.98) | OM = -33.1 + 3.7 TL | 0.4059 |
OM = -28.1 + 4.1 SL | 0.5360 | |||
OM = -34.17 + 4.3 FL | 0.5894 | |||
Otolith length (mm) | 9.68 – 14.69 | 12.19 (0.11) | OL = 260 + 63.4 TL | 0.7216 |
OL = 219 + 74.9 SL | 0.7001 | |||
OL = 156 + 72.9 FL | 0.7280 | |||
Otolith width (mm) | 8.61 – 12.35 | 10.48 (0.13) | OW = 316 + 43.5 TL | 0.6461 |
OW = 366 + 50.7 SL | 0.6093 | |||
OW = 305 + 50.5 FL | 0.6663 | |||
Otolith mass (g) | 11 – 33 | 22 (0.97) | OM = 1.45 + 1.9 TL | 0.1717 |
OM = 1.66 + 1.6 SL | 0.1828 | |||
OM = -1.75 + 1.7 FL | 0.2257 |
There needs to be more data on the relationship between otolith biometrics and the size of the fish of Cyprinid fish from Turkish inland waters. In the present investigation, the relationships between OL, OW, and OM with the total fish length for
The significant relation between the otolith biometrics and body size explains the effect of body growth on the otoliths of the fish examined (Munk 2012). This linear relation is dependent relative to the growth rate of each species (Campana & Casselman 1993, Mugiya & Tanaka 1992). Most investigators have shown close relationships between somatic and otolith growth (Giménez et al. 2016, Jawad et al. 2017, See et al. 2016). In addition, the linear relation can be adjusted for different size groups (Hare & Cowen 1995). Nevertheless, in the present work, using the three fish lengths of both species studied, the linear pattern best fits the relationship between body size and the otoliths in some biometrics (see results). This showed to have a very significant correlation (
The reason behind developing more than one equation that links the fish’s size with the otolith’s biometric features is the occurrence of damage on the margins of the otoliths, as shown by several studies (de Assis et al. 2018). Even though the determination coefficient estimates were well represented in the results, the equations produced should be used cautiously. The shape and size of otoliths are affected by genetic, ontogenetic, and environmental characteristics (Campana & Casselman 1993). The shape is genetically affected, and the size relies on temperature and the existence of carbonate in the water (Checkley et al. 2009, Lombarte & Lleonart 1993), which can cause variations in the relation between otoliths and body size in populations from different locations. A further crucial aspect is the disclosure of chemicals in the digestive system of the predators, which can influence assessing prey size due to degradation to the surface of the otolith produced by stomach acids (Granadeiro & Silva 2000, Jobling & Breiby 1986). Contemplating these problems to lessen errors, we suggest using the equations generated in the present study in the Turkish waters, given that temperature influences the formation of otoliths, and to look for the existence of degradation from digestion. Nevertheless, the results show that estimates of the species’ body size using biometric analyses of otoliths are reliable.
Nonetheless, the taxonomic value of the otolith of
The investigation provides various provisions for the biometric relationships between asteriscus otolith biometrics and total fish length for Cyprinid fish caught in inland waters in Türkiye. Significant relationships between otolith mass and the three fish lengths (TL, SL, and FL) were attained for