What does this message mean (and how do i fix it)

I keep getting this error message for an entity im trying to make. I cant make any sense of it, nor can i figure out what the problem is. Please help.

Executing Gradle task: runClient
Build info: MCreator 2021.1.18117, forge-1.16.5, 64-bit, 12063 MB, Windows 10, JVM 1.8.0_275, JAVA_HOME: C:\Program Files\Pylo\MCreator\jdk
> Task :compileJava FAILED
C:\Users\oelta\MCreatorWorkspaces\sharks\src\main\java\net\mcreator\sharks\entity\renderer\SharkRenderer.java:52: error: variable left_fin is already defined in class Modelshark_model private final ModelRenderer left_fin;
^
1 error
FAILURE: Build failed with an exception.
* What went wrong:
Execution failed for task ':compileJava'.
> Compilation failed; see the compiler error output for details.
* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.
* Get more help at https://help.gradle.org
BUILD FAILED in 2s
1 actionable task: 1 executed
BUILD FAILED
Task completed in 5 seconds