Reasons why they might not be considered Igbo
1. They are found west of the River Niger.

2. They are in Delta state of the south south region (a less than 40 years old grouping).

3. Some of their communities have monarchs.

4. Some Aniomas say that they are not Igbos.

Reasons why they might be considered Igbo
1. They speak Igbo and Igboid dialects.

2. They bear Igbo names.

3. They share same culture with South Easterners, evident in dance, music, festivals, rituals even to the ceremonial breaking of kola nuts.

4. They have same political system with South Easterners, some communities are headed by a council of heads of different families, most of the monarchies are not hereditary and the few that are very inabsolute.

5. Folklore
The traditional tales told, even the myths that explain the origin of communities are Igbo like and almost always has an Igbo progenitor.

6. Ekwumekwu war
The 3 decade war fought by the Aniomas in present day Delta state and people of Onicha Udo (Onitsha ) and other neighbouring communities against British colonialists was orchestrated and planned in unison in Igbo.

7. Most Aniomas say that they are Igbos, some need not say it, they simply dress it like my amiable governor
His Excellency Dr. Ifeanyi Arthur Okowa with his signature red cap.


Sources
https://en.m.wikipedia.org/wiki/Anioma_people

http://aniomawatch..com/2013/08/biniigbo-factors-origins-and-migration.html?m=1

http://aniomaga.org/this-is-article-test-2/

http://asaba.com