The alabarch was the Greek title of the customs official at the harbour of Alexandria during the Hellenistic and Roman periods. The title 'alabarch' needs to be distinguished from the title of 'ethnarch' which refers to the chief magistrate of a particular ethnic group within a city or territory.
It appears that some confusion exists as to the meaning of this word and even the Shorter Oxford English Dictionary makes the mistake of assuming that alabarch somehow equals ethnarch.
The following references should suffice to establish the meaning of the word alabarch:
Smallwood, E. Mary, The Jews Under Roman Rule. Leiden, 1976. P 227.
Philo's brother Alexander was alabarch (customs official) in the 30's A.D., and another Jew, Demetrius (otherwise unknown) held the same post late in Claudius' principate; neither case excites comment from Josephus as unusual.
Modrzejewski, Joseph M, The Jews of Egypt: From Rameses II to Emperor Hadrian. Jewish Publication Society. 1995. P 135.
(regarding Alexander the alabarch) ...he was inspector-in-chief of customs (alabarch) and not a banker, evenif he did occasionally lend sums of money, for instance to his eternally indebted friend, Agrippa I King of Judea.
The following alabarchs are known by name: