Development of empirical standard weight equation for Pursak chub Squalius pursakensis, an endemic cyprinid species of Northwest Anatolia

Abstract

Indices of condition enable the evaluation of the well-being of fish, with the assumption that heavier fish of a given length are in a better condition. Relative weight (W r ) is one of these indices; it is calculated by comparing the actual weight of a specimen with the ideal weight of a specimen in good physiological condition of the same length from the same species, i.e. standard weight (W s ). In this research, length and weight data over the distribution range for Pursak chub Squalius pursakensis, an endemic species distributed in the Sakarya and Porsuk drainages in Northwest Anatolia (Turkey), were used to compute a W s equation by means of the empirical percentile (EmP) method. The W s equation obtained was log 10 W s = -4.657 + 2.614 log 10 TL + 0.127 (log 10 TL) 2 , and the total length range of application was 80-340 mm. Since the EmP W s equation was not influenced by length variation, the use of this equation to compute the relative weight (W r ) for S. pursakensis throughout its area of distribution is suggested.

Growth and life history traits of Aegean chub, Squalius fellowesii (Günther, 1868) in streams in Muğla Province, Aegean coast, Turkey

“…Because these species are recent descriptions, very little information is available (e.g. Gianetto et al., ; Sülün et al., ); however, the IUCN Red List of Threatened Species (IUCN, ) has recently assessed S. fellowesii as being of ‘Least Concern’.…”

Standard weight equations of two sub-/tropic nonnative freshwater fish, Clarias gariepinus and Oreochromis niloticus , in the Sakarya River Basin (NW Turkey)

“…All the anomalous values (outliers) were removed from the regressions because they were almost certainly the consequence of incorrect measurements in the field (Bister et al, 2000). For each species, the total dataset was divided into "statistical populations" with every population consisting of data collected at the same sampling location (Sülün et al, 2014). The estimation of a W s equation includes the preliminary determination of a proper range-length: a minimum and a maximum length of applicability.…”

“…While the methodology is currently commonly used in the United States (Blackwell et al, 2000), its use in other countries is still limited, probably because of the lack of specific W s equations (Giannetto et al, 2015a). With regard to Turkey, specific W s equations are currently available only for some endemic freshwater species (Giannetto et al, 2012c;Sülün et al, 2014;Giannetto et al, 2015b;2019).…”

Length–weight and length–length relationships for three endemic cyprinidspecies of the Aegean region (Turkey) with proposed standard weight equations

“…From the results of the validation analyses conducted, the W s equations developed for B. pergamonensis, C. bergamae, and L. irideus were found not to be affected by length-related bias; their use in evaluating the W r of the species across the watercourses of Muğla Province is thus recommended. These equations provide very useful species-specific tools to compare and evaluate the condition (well-being status) of endemic species living in different habitats and specimens of different lengths (e.g., Sülün et al, 2014). Furthermore, these data could be very informative for identifying important conservation areas where the species' conditions are high for special restocking practices, and for species' conservation and habitat rehabilitation for populations with lower body conditions (e.g., Giannetto et al, 2012c).…”

“…With reference to endemic Turkish species, specific W s equations were developed for Aegean chub Squalius fellowesii (Giannetto et al, 2012c), another endemic species in the same region as the species studied in the present work, and Pursak chub S. pursakensis from the Marmara region (Sülün et al, 2014).…”