It's a poker term meaning a weak player. I haven't really heard it in relation to chess though.
"goddamn fish"

It's a poker term meaning a weak player. I haven't really heard it in relation to chess though.
"Rabbit" is more usual.

Fischer used the term quite a bit.
"After the games were adjourned, all the Soviets would go back to Spassky's hotel room to plan for the next position," recalls Don Schultz, one of the seconds. "Lombardy said to Fischer, 'That's a difficult position. Let's go back to the hotel and analyze it.' Fischer said, 'What do you mean, analyze? That guy's a fish. Let's go bowling.'"

It's a poker term meaning a weak player. I haven't really heard it in relation to chess though.
"Rabbit" is more usual.
That's because you are from the UK. In the US players use the term "fish" like you use the term "rabbit." Generally helpless animals in either case.

Fischer used the term quite a bit.
"After the games were adjourned, all the Soviets would go back to Spassky's hotel room to plan for the next position," recalls Don Schultz, one of the seconds. "Lombardy said to Fischer, 'That's a difficult position. Let's go back to the hotel and analyze it.' Fischer said, 'What do you mean, analyze? That guy's a fish. Let's go bowling.'"
He probably used the term Fisch
Can someone help me with slang? What does it mean when someone calls me a "goddamn fish"?
He ran out of time. Perhaps he was angry that I wasn't more aggressive?