AGE, GROWTH AND OTOLITH BIOMETRY-BODY LENGTH RELATIONSHIPS OF RED BANDFISH ( Cepola macrophthalma L., 1758) IN THE SEA OF MARMARA, TURKEY

: The age, growth, and the otolith biometry-total length relationships of Cepola macrophthalma (Linnaeus, 1758) were investigated. The individuals were caught with beam trawl in the Sea of Marmara from March 2012 to 2014. The individual with 51.5 cm total length sampled in this study was recorded as the new maximum size of C. macrophthalma in the Marmara Sea. The length-weight relationship showed negative allometric growth with a 1.36 b value. Otolith length-otolith weight, otolith width-otolith weight, otolith length-total length, otolith width-total length, otolith length-otolith and total length-otolith weight relationships were found as were from 80 otolith readings and the minimum and maximum ages observed were 1 and 5 years, respectively. The growth parameters of the von Bertalanffy equation were calculated as L ∞ =61.95 cm, K=0.19 year -0.05 years. A great majority of the stock (77%) consisted of younger individuals (1-2 age groups). Cepola consisted of mainly younger individuals which may indicate that an effective fishing pressure is effective on the stock.


Introduction
The red bandfish, Cepola macrophthalma (Linnaeus, 1758) is a marine demersal fish species that inhabit soft and muddy bottoms at depths ranging from 15 to 400 m (Sanches 1991). It usually lives in vertical burrows and distributes singly or in groups. There is little information about early life stages of the species except that the eggs are pelagic. The main food source of the species are small crustaceans and chaetognaths (Whitehead et al. 1986). The maximum size of the species has been recorded as 80 cm TL in the Biscay Bay (Sanchez et al. 1995) but the mean length is at about 40 cm in Guiné-Bissau costs in the Atlantic Ocean (Sanches 1991). The details of ecology and life history of C. macrophthalma is poorly known. Although it is known as an eastern Atlantic origin species, it has an extensive geographical distribution from the Strait of Gibraltar to northern Senegal; northward extending into the Canary Islands, the Mediterranean and north Atlantic up to Scotland and the Orkney Islands (Smith-Vaniz 2015).
In the Mediterranean, C. macrophthalma is present in the Catalan Sea (Coll et al. 2006), the Gulf of Lions (Gaertner et al. 1998), the Ligurian Sea (Molinari & Tunesi 2003), the Tyrrhenian Sea (Colloca et al. 2004, Carpentieri et al. 2005, the Cretan Sea (Kallianiotis et al. 2000), the Aegean Sea (Stergiou 1999 The aim of this study is to estimate the relationship between otolith size and fish size, age and growth parameters of C. macrophthalma in the Sea of Marmara. We reported the first results on the age and growth of C. macrophthalma in the Sea of Marmara and the first results about otolith and fish morphometric relationships in general.

Materials and Methods
A total of 105 C. macrophthalma specimens were sampled in the Sea of Marmara with monthly samplings between March 2012 and June 2014 from, (Fig. 1). The samplings were carried out using a commercial beam trawl net. Total length (TL) and weight (W) values of the samples were determined to the nearest 1 mm and 0.01 g, respectively. The length-weight relationship was determined according to the formula of Le Cren (1951): W=a*L b , where W is the total body weight (g), L is the total length (cm) while a and b are constants. To check whether fish growth is statistically different from isometric growth (b=3) Student's t-test was used by the equation according to Sokal & Rohlf (1987): ts=(b-3)/SE(b), where ts is the t-test value, b is the slope and SE(b) is the standard error of the b value.
The ages of 80 specimens were determined using the sagittal otoliths, while the rest 25 otoliths were not evaluated as they were broken to a degree which made it impossible to determine their age. The otolith is the most commonly used material for age estimation (Holden & Raitt 1974) and was commonly used for age determination of C. macrphthalma (Kaya et al. 2001, Leblebici 2007. The otolith of this species is easly readible. The nucleus is totally opaque, first translucent band starts after the opaque zone. Estimation of age was based almost exclusively on the interpretation of otolith structures for the presence of translucent and opaque zones which are assumed to represent winter and summer growth periods and the date of birth is assumed 1 January. Sagittal otoliths from each fish were removed and cleaned. The size of the otoliths was measured with Q-Capture Digital Imaging Software attached on an Olympus SZX-7 stereomicroscope with a camera sensitivity to 0.01 mm and weighed with the precision of 0.0001 g by scales (Fig. 2). Annual rings on the whole otoliths were counted in glycerin under a stereomicroscope. The translucent and opaque zones were counted for age determination. The otoliths were read by three different observers and age was determined when minimum two of the readings agreed.  Otolith length (OL), otolith width (OWi) and otolith weight (OW) were measured in all otoliths as shape parameters. For the analysis of relationships between OL-OW, OWi-OW, OL-TL, OWi-L, OL-OWi and TL-W, the equation y=ax+b was used where y is OW, OWi or OL, x is TL or OL, and equation y=ax b where y is OW, x is OL or OWi, and a and b are constant coefficients. The chosen regression model was decided based on the magnitude of the R 2 value.
Growth parameters were determined using the von Bertalanffy equation (Beverton & Holt 1957): Lt=L∞ (1e -K(t-t 0 ) ), where L∞ is the asymptotic total length, Lt the total length at age t, K the growth curvature parameter and t0 is the theoretical age when fish would have been at zero total length. Growth parameters were estimated using the "Analyze of length at age data" method in FAO-ICLARM Stok Assessment Tools (FISAT II) software. For the sake of comparison, the index of overall growth performance Ф proposed by Pauly & Munro (1984) was calculated. This test indicated the reliability of age estimates since it had been suggested that phi-prime test values were similar for the same species and genera. The test was based on Ф = logK+2*logL∞ (Pineiro & Sainza 2003).
All statistics were analyzed using the MINITAB 16 program. The normality assumptions were checked with Kolmogorov-Simirnov test. Student's t-test was used for analyzing the fish growth type. Paired t-test was used to test whether there is a difference between right and left otoliths. The regression models were used to explain relationships between fish and otolith morphometry.

Results
A total of 105 specimens ranged from 8.5 to 51.5 cm in TL and from 1.65 to 24.54 g in weight. A pair of 80 sagittal otoliths were measured. Otolith length, weight and width measurements are given in Table 1. There was no significant difference between right and left otoliths (paired t-test, P=0.63), therefore, only right otoliths (n=80) were used for further analysis. Length-weight relationship was calculated as W=0.126*TL 1.36 (R 2 =0.74) and showed a negative allometric growth pattern (Fig. 3). Otolith length-otolith weight, otolith width-otolith weight, otolith length-total length, otolith width-total length, otolith length-otolith width and total length-otolith weight relationships were found as OW=0.  (Fig. 4).
The age interval ranged between 1 and 5. The highest represented age group was 2 (46%) and the age group 1 (30%) and age group 3 were considerably well represented ( Table 2).

Discussion
The life span of the C. macropthalma is shorter than many demersal fish species (Dulčić et al. 2008). According to our results, the oldest individual was 5 years old. A great number of limiting factors may have contributed to the occurrence of a shorter life span, as high fishing pressure, nutritional inadequacy, morphological characteristics of the species, etc. The same results were observed in studies conducted in the eastern Adriatic (Dulčić et al. 2008), Adriatic (Vallisneri et al. 2006), Izmir Bay (Kaya et al. 2001) and Euboikos Gulf, western Aegean Sea (Stergiou & Papaconstantinou 1993). In contrast, relatively long life spans were determined in studies conducted in the British Isles (Atkinson 1976) and in Pagassitikos Gulf, western Aegean Sea (Stergiou & Papaconstantinou 1993). This may be a result of lower fishing pressure and availability of more sheltering areas for C. macropthalma in these areas. Its elongated, laterally compressed body shape [horizontal dimension 16 times the vertical one, Stergiou & Papaconstantinou (1993)] may be advantageous for escaping from the mesh of fishing nets. Barely squeeze in the trawl and beam trawl bag prevents occurring of this advantage. It's slow, wavy mode of swimming (Wilson 1953) may make the species an open target for fishing vessels. The observed short life span in a great majority of studies caused us to focus on fishing pressure. Trawl fishing is the main reason for fishing pressure on demersal species. Demersal trawling is prohibited in the Sea of Marmara. Conversely, beam trawl fishery is legally allowed and extensively applied. The relatively lower growth rate and shorter life span may have resulted from the high fishing pressure of beam trawl fishery in the Marmara Sea. The age-frequency distribution also supports this finding. A majority of individuals were of age groups 1 and 2.
The b value shows negative allometry (Student t-test). Negative allometry is mandatory due to the physical nature of the species. The exponent b usually varies between 2.5-3.5 for other fish species. Merely, the lifestyle of C. macrophthalma may cause unproportional length increases according to growth in weight, and this may induce lower b values (Froese 2006). However, the calculated b value (1.358) in this study reveals the lowest value compared with the others (Table 3) Due to the absence of studies on the age and growth parameters of C. macropthalma in the Sea of Marmara, growth parameters were compared with other studies conducted in adjacent waters. In almost all studies, the calculated L∞ and K values are greater than the ones in this study. The estimated L∞ and K values in our study are in agreement with the findings of Stergiou et al. (1992). Also, the same K value was obtained in the findings of Kaya et al. (2001), whereas our calculated L∞ value is lower. We think this may be due to the high number of smaller individuals in our data set (Table 4). Since otolith biometry (shape, size, etc.) varies according to to size of the fish species, the relationship between otolith biometry and fish length can be useful for species identification and prey length from the otoliths found in stomach content (Campana & Thorrold 2001). Besides, it can be used by archaeologists to reveal the mystery from excavation (Hajkova et al. 2003). Otolith biometry fish length relationship has been carried out for many species (Appelbaum & Hechte 1978, Hare & Cowen 1995, Hoşsucu et al. 1999, Bostancı 2009, Park et al. 2018). This study reveals the first results for otolith biometry-total length relationship approach of C. macrophthalma. The morphological difference was not found between the left and right otoliths (paired t-test, p=0.63). Therefore the researchers studying on C. macrophthalma can use both otoliths in their calculations.
Because of its minor commercial interest, C. macrophthalma is listed as Least Concern in the IUCN Red List of Threatened Species (IUCN 2015). According to IUCN, the species has been assessed lastly in 2013 and its population trend is identified as unknown. In addition, the stocks of mature individuals are stated to show a decline trend. Cepola macrophthalma is occasionally fished for utilizing fresh, fish soup, fish oil or fishmeal (Whitehead et al. 1986) especially around Spain, Portugal and along the West African coasts. Although it has no commercial value, it is known to have a high discard rate in trawling fishery in the Aegean and the Mediterranean Sea and the Sea of Marmara in Turkey. Knowledge of specific conservation measures for C. macrophthalma is unknown, and there exists not enough scientific work to take protective measures in the Sea of Marmara. More detailed further studies should be advised especially on the biology and population dynamics.