Identity of Squalius (Actinopterygii, Cyprinidae) from Istra Peninsula in Croatia (Adriatic Sea basin)

Nina Bogutskaya,Alexander Naseka,Milorad Mrakovčić,Zoran Marčić,Primoz Zupančič

doi:10.3897/zookeys.53.472

Abstract

A chub of previously ambiguous identity from the Boljunscica and Pazincica rivers (south-eastern Istra Peninsula) was studied and compared with geographically close Squalius squalus, Squalius zrmanja, and Squalius janae recently described from the Dragonja River drainage in the Adriatic Sea basin in Slovenia. It was shown that the chub from the south-eastern Istra Peninsula differs from all know species of Squalius but one: Squalius janae. Three samples examined from Boljunscica and Pazincica rivers and Squalius janae from its type locality, Dragonja River, show the following characters typical for the latter species: a long head (the head length 27–32% SL); a pointed conical snout with a clearly projecting upper jaw; a long straight mouth cleft, the lower jaw length (39–45% HL) exceeding the caudal peduncle depth; a large eye; commonly 9? branched anal-fin rays; commonly 44 total vertebrae (24+20 or 25+19); bright silvery colouration, scales easily lost; iris, pectoral, pelvic and anal fin pigmentation with yellow shades. The data on the distribution of Squalius chubs in the northern Adriatic basin support the assumption that the range of Squalius janae is determined by the geology of the Trieste Flysch Basin and the Pazin Flysch Basin forming the base of the Istra Peninsula. The distribution pattern of this species does not support a simple model of fish dispersal and a complete connectivity within the whole Palaeo-Po historical drainage. Indeed, it indicates a disrupted surface palaeohydrography that was heavily fragmented by karstification in the whole Dinaric area.

Highlights

Istra [Istria, formerly Histria], is the largest peninsula in the Adriatic Sea. It is located in the northern Adriatic between the Gulf of Trieste and the Bay of Kvarner, and shared by three countries: Croatia, Slovenia and Italy
Larger rivers of the western cost of the Istra Peninsula are Osapska Reka [Osbo], Rižana [Risano], Badaševica [Kornalunga], Dragonja with its largest tributary Pinjevec [Rokava], and Mirna [Quieto], which is the largest river in Istra
The purpose of the present article is to describe the chub from Pazinčica and Boljunšćica rivers, compare it with S. janae and S. squalus, and decide on its identity

Summary

Introduction

Istra [Istria, formerly Histria], is the largest peninsula in the Adriatic Sea. It is located in the northern Adriatic between the Gulf of Trieste and the Bay of Kvarner, and shared by three countries: Croatia, Slovenia and Italy. Larger rivers of the western cost of the Istra Peninsula are (from north to south) Osapska Reka [Osbo], Rižana [Risano], Badaševica [Kornalunga] (with a reservoir called Vanganel Lake), Dragonja with its largest tributary Pinjevec [Rokava], and Mirna [Quieto], which is the largest river in Istra. The Butoniga River, a tributary of the Mirna, was dammed in 1989 in its upper part and flows into a reservoir called Butoniga Lake. Rivers Raša [Arsia] (flowing into the Raški Zaljev [Raski Inlet, Porto d’Arsia] and Boljunšćica [Boljunčica] (used to flow into the Plumin Luka Inlet or Plumin Bay) go southwards along the western slope of the Učka mountains [Monte Maggiore] and the Ćićarija [Ciceria] mountain range. Till 1932 Čepić Polje had been a lake, which is drained

Objectives

Methods

Results