Go Back To Main Menu Keeps Looping Menus

This is relying on a feature called implicit function declarations; this is considered harmful and was removed in C99. One might rearrange the menus to be on top, or prototype the functions before calling them,

int mainMenu(void);
int FishermanMenu(void);

and change the implicit int parameter to a local variable that is returned,

int mainMenu(void) {
    int MOption;
...
}
int FishermanMenu(void) {
    int FManOption;
...
}

EDIT

Instead of figuring out the mess of switches that is only going to get worse to debug, let me suggest a change in application structure. This code could be a state machine without many changes, just return the next state from the function.

enum states {
    START, MAIN, FISHPERSON, REGISTER, SEARCH, FISH, CATCH, CLOSE, END
};

enum states StartMenu(void);
enum states MainMenu(void);
enum states FishermanMenu(void);
/* ... */

typedef enum states (*state_function)(void);
static const state_function states[] = { StartMenu, MainMenu,
    FishermanMenu, /*...*/0, 0, 0, 0, 0, /* END is actually 0 == NULL */0 };

int main(void)
{
    enum states state = START;
    while(states[state]) state = states[state]();
    return 0;
}

Then one returns the state from the menu,

enum states StartMenu(void) {
    int userChoice = 0;
    //process:
    printf("Please select 1 to start the program or 0 to quit: ");
    scanf("%d", &userChoice);
    while(userChoice != 1 && userChoice != 0)
    {
        printf("Invalid selection! Please type a 1 or a 0: ");
        scanf("%d", &userChoice);
    }//end (userChoice != 1 && userChoice != 0)
    if(userChoice != 1) {
        printf("Thank you for wasting my time! Have a great day!");
        return END;
    } else {
        return MAIN;
    }
}

To repeat less, instead of a while() {} consider a do {} while() on menus that display the information up front.

I figured it out. My professor was able to help me as he responded to my email later than usual. My problem was I needed to add a while loop for the entire set of menus with MOption = mainMenu(); and assign each menu option to their respective functions. Thank you all who responded I greatly appreciate your time! Here is the updated code:

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>

int main()
{
    //declare all working variables: mOption, FManOption, COption...etc...
    int MOption = 0;
    int FManOption = 0;
    int FOption = 0;
    int COption = 0;
    int userChoice = 0;

    //declarations for all arrays of struct
    //declare a pointer to an array of struct using malloc() for fisherman, fish, catch

    //process:
    printf("Please select 1 to start the program or 0 to quit: ");
    scanf("%d", &userChoice);
    while(userChoice != 1 && userChoice != 0)
    {
        printf("Invalid selection! Please type a 1 or a 0: ");
        scanf("%d", &userChoice);
    }//end (userChoice != 1 && userChoice != 0)
    if(userChoice != 1)
    {
        printf("Thank you for wasting my time! Have a great day!\n");
        return 0;
    }
        while(MOption != 5)
        {

            MOption = mainMenu();
            switch(MOption)
            {
            case 1: FManOption = FishermanMenu();
                    while(FManOption != 3)
                    {
                        switch(FManOption)
                        {
                            case 1: //get a fisherman
                                    //count fisherman
                                    break;
                            case 2: //prompt for a ssn, validate, search
                                    //if found display everything about this fisherman
                                    break;
                            case 3: FManOption = mainMenu();
                                    //reset FManOption
                                    break;
                            default: printf("\nInvalid selection! Please select from one of the menu options\n");
                        }//end switch(FManOption)
                    }//end while(FManOption != 3)
                    break;
        }
    }
}

int mainMenu(MOption)
{
    printf("\n-------Welcome to the Fishing Tournament Main Menu!-------\n");
    printf("1 - Fisherman menu\n");
    printf("2 - Fish menu\n");
    printf("3 - Tournament(Catch) menu\n");
    printf("4 - Close Tournament (determine winner)\n");
    printf("5 - Quit Program\n\n");
    printf("Please select a menu option: ");
    scanf("%d", &MOption);
    if(MOption > 5 || MOption < 1)
        do /* check scanf() return value for input errors */
        {
            printf("\nInvalid selection! Please select from one of the menu options\n");
            printf("1 - Fisherman menu\n");
            printf("2 - Fish menu\n");
            printf("3 - Tournament(Catch) menu\n");
            printf("4 - Close Tournament (determine winner)\n");
            printf("5 - Quit Program\n\n");
            printf("Please select a menu option: ");
            scanf("%d", &MOption);
        }
        while(MOption > 5 || MOption < 1);

    return MOption; /* finally return the final correct option */
}//end main menu

int FishermanMenu(FManOption)
{
    printf("\n-------Fisherman Menu-------\n");
    printf("1 - Register fisherman\n");
    printf("2 - Search fisherman\n");
    printf("3 - Go back to main menu\n");
    printf("Please select a menu option: ");
    scanf("%d", &FManOption);
    if(FManOption > 5 || FManOption < 1)
        do /* check scanf() return value for input errors */
        {
            printf("\nInvalid selection! Please select from one of the menu options\n");/* handle input error */
            printf("1 - Register fisherman\n");
            printf("2 - Search fisherman\n");
            printf("3 - Go back to main menu\n");
            printf("Please select a menu option: ");
            scanf("%d", &FManOption);
        }
        while(FManOption > 5 || FManOption < 1);
    return FManOption; /* finally return the final correct option */
}//end Fisherman Menu

The problem is that you get stuck in this while loop forever:

while (FManOption != 3)

This loop only makes sense when you are inside the "Fisherman" sub-menu, but you should leave this loop and return the program to its previous state after the user selects "Go back to main menu".

Instead of attempting to write your code in such a way that the state of the program (e.g. whether the user is currently in the main menu or a sub-menu) is implied by the control flow of the program, it is often easier to store the program state explicitly in a variable, for example like this:

enum menu_state
{
    MENUSTATE_MAIN,
    MENUSTATE_FISHERMAN,
    MENUSTATE_FISH,
    MENUSTATE_TOURNAMENT_CATCH,
    MENUSTATE_CLOSE_TOURNAMENT
};

int main( void )
{
    [...]
    if (userChoice != 1)
        printf("Thank you for wasting my time! Have a great day!");
    else
    {
        enum menu_state ms = MENUSTATE_MAIN;

        for (;;) //infinite loop, equivalent to while(true)
        {
            switch ( ms )
            {
                case MENUSTATE_MAIN:
                    switch ( mainMenu() )
                    {
                        case 1:
                            printf( "opening fisherman menu\n" );
                            ms = MENUSTATE_FISHERMAN;
                            break;
                        case 2:
                            printf( "opening fish menu\n" );
                            ms = MENUSTATE_FISH;
                            break;
                        case 3:
                            printf( "opening tournament(catch) menu\n" );
                            ms = MENUSTATE_TOURNAMENT_CATCH;
                            break;
                        case 4:
                            printf( "opening close tournament menu\n" );
                            ms = MENUSTATE_CLOSE_TOURNAMENT;
                            break;
                        case 5:
                            //quit program
                            exit( EXIT_SUCCESS );
                        default:
                            fprintf( stderr, "unexpected error\n" );
                            exit( EXIT_FAILURE );
                    }
                    break;
                case MENUSTATE_FISHERMAN:
                    switch ( FishermanMenu() )
                    {
                        case 1:
                            printf( "Register fisherman not yet implemented.\n" );
                            break;
                        case 2:
                            printf( "Search fisherman not yet implemented.\n" );
                            break;
                        case 3:
                            //change program state back to main menu
                            ms = MENUSTATE_MAIN;
                            break;
                        default:
                            fprintf( stderr, "unexpected error\n" );
                            exit( EXIT_FAILURE );
                    }
                    break;
                case MENUSTATE_FISH:
                    printf( "Fish menu not yet implemented, returning to main menu.\n" );
                    ms = MENUSTATE_MAIN;
                    break;
                case MENUSTATE_TOURNAMENT_CATCH:
                    printf( "Tournament(catch) menu not yet implemented, returning to main menu.\n" );
                    ms = MENUSTATE_MAIN;
                    break;
                case MENUSTATE_CLOSE_TOURNAMENT:
                    printf( "Close tournament not yet implemented, returning to main menu.\n" );
                    ms = MENUSTATE_MAIN;
                    break;
                default:
                    fprintf( stderr, "unexpected error\n" );
                    exit( EXIT_FAILURE );
            }
        }
    }
}

It is also worth noting that your functions mainMenu and FishermanMenu contain unnecessary code duplicaton. You can simplify the function mainMenu the following way:

int mainMenu( void )
{
    for (;;) //repeat forever, until input is valid
    {
        int option;
        printf("\n-------Welcome to the Fishing Tournament Main Menu!-------\n");
        printf("1 - Fisherman menu\n");
        printf("2 - Fish menu\n");
        printf("3 - Tournament(Catch) menu\n");
        printf("4 - Close Tournament (determine winner)\n");
        printf("5 - Quit Program\n\n");
        printf("Please select a menu option: ");
        scanf("%d", &option);

        if ( 1 <= option && option <= 5 )
            return option;

        printf("\nInvalid selection! Please select from one of the menu options\n");
    }
}

However, it is important to always check whether the function scanf succeeded before attempting to use the result of scanf. This can be accomplished by checking the return value of scanf. Also, after using scanf, it is important to discard the input from the rest of the line. Otherwise, if the user for example enters "12dfghoh", then all subsequent calls to scanf will fail, because it won't be able to remove dfghoh from the input stream when trying to read a number.

Therefore, here is the code in which I check the return value of scanf and also discard all remaining input in the line:

int mainMenu( void )
{
    for (;;) //repeat forever, until input is valid
    {
        int option, c;

        printf("\n-------Welcome to the Fishing Tournament Main Menu!-------\n");
        printf("1 - Fisherman menu\n");
        printf("2 - Fish menu\n");
        printf("3 - Tournament(Catch) menu\n");
        printf("4 - Close Tournament (determine winner)\n");
        printf("5 - Quit Program\n\n");
        printf("Please select a menu option: ");
        if (
            scanf("%d", &option) == 1 && //make sure scanf succeeded
            1 <= option && option <= 5
        )
        {
            return option;
        }

        printf("\nInvalid selection! Please select from one of the menu options\n");

        //discard remainder of line, which may contain bad input
        //and prevent the next call of scanf to succeed
        do
        {
            c = getchar();
        }
        while ( c != EOF && c != '\n' );
    }
}

On the other hand, for line-based input, it would probably be better to use fgets instead of scanf, because then you don't have to deal with removing bad input from the input stream. See this link for further information:

A beginners' guide away from scanf()

Using the fgets function, the function mainMenu would look like this:

//NOTE: the following header must be added
#include <ctype.h>

int mainMenu( void )
{
    for (;;) //repeat forever, until input is valid
    {
        char buffer[1024], *p;
        long option;

        printf("\n-------Welcome to the Fishing Tournament Main Menu!-------\n");
        printf("1 - Fisherman menu\n");
        printf("2 - Fish menu\n");
        printf("3 - Tournament(Catch) menu\n");
        printf("4 - Close Tournament (determine winner)\n");
        printf("5 - Quit Program\n\n");
        printf("Please select a menu option: ");

        if ( fgets( buffer, sizeof buffer, stdin ) == NULL )
        {
            printf( "unexpected input error!\n" );

            //since this type of error is probably not recoverable,
            //don't try again, but instead exit program
            exit( EXIT_FAILURE );
        }

        option = strtol( buffer, &p, 10 );

        if ( p == buffer )
        {
            printf( "error converting string to number\n" );
            continue;
        }

        //make sure remainder of line contains only whitespace,
        //so that input such as "12dfghoh" gets rejected
        for ( ; *p != '\0'; p++ )
        {
            if ( !isspace( (unsigned char)*p ) )
            {
                printf( "unexpected input encountered!\n" );
                continue;
            }
        }

        //make sure input is in the desired range
        if ( option < 1 || option > 5 )
        {
            printf( "input must be between 1 and 5\n" );
            continue;
        }

        return option;
    }
}

However, you cannot simply replace the function mainMenu in your code with my code above, because mixing scanf and fgets in your code will not work very well. This is because scanf will not read one line at a time from the input stream, but will only extract as much as it needs to read the number and will leave the rest of the line, including the newline character, in the buffer. Therefore, if you use fgets immediately after scanf, fgets will read the remainder of the line that scanf did not extract, which will be often a string containing nothing else than the newline character.

Therefore, if you decide to use fgets (which I recommend), then you should use it everywhere in your program and not mix it with scanf, for example like this:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <limits.h>
#include <errno.h>

int mainMenu(void);
int FishermanMenu(void);
int get_int_from_user( const char *prompt );

enum menu_state
{
    MENUSTATE_MAIN,
    MENUSTATE_FISHERMAN,
    MENUSTATE_FISH,
    MENUSTATE_TOURNAMENT_CATCH,
    MENUSTATE_CLOSE_TOURNAMENT
};

int main( void )
{
    int user_choice;

    for (;;) //loop forever until input is valid
    {
        user_choice = get_int_from_user(
            "Please select 1 to start the program or 0 to quit: "
        );

        if ( user_choice == 0 )
        {
            printf("Thank you for wasting my time! Have a great day!");
            exit( EXIT_SUCCESS );
        }

        if ( user_choice == 1 )
        {
            //input is valid, so break infinite loop
            break;
        }

        printf( "Invalid selection!\n" );
    }

    enum menu_state ms = MENUSTATE_MAIN;

    for (;;) //main program loop
    {
        switch ( ms )
        {
            case MENUSTATE_MAIN:
                switch ( mainMenu() )
                {
                    case 1:
                        printf( "opening fisherman menu\n" );
                        ms = MENUSTATE_FISHERMAN;
                        break;
                    case 2:
                        printf( "opening fish menu\n" );
                        ms = MENUSTATE_FISH;
                        break;
                    case 3:
                        printf( "opening tournament(catch) menu\n" );
                        ms = MENUSTATE_TOURNAMENT_CATCH;
                        break;
                    case 4:
                        printf( "opening close tournament menu\n" );
                        ms = MENUSTATE_CLOSE_TOURNAMENT;
                        break;
                    case 5:
                        //quit program
                        exit( EXIT_SUCCESS );
                    default:
                        fprintf( stderr, "unexpected error\n" );
                        exit( EXIT_FAILURE );
                }
                break;
            case MENUSTATE_FISHERMAN:
                switch ( FishermanMenu() )
                {
                    case 1:
                        printf( "Register fisherman not yet implemented.\n" );
                        break;
                    case 2:
                        printf( "Search fisherman not yet implemented.\n" );
                        break;
                    case 3:
                        //change program state back to main menu
                        ms = MENUSTATE_MAIN;
                        break;
                    default:
                        fprintf( stderr, "unexpected error\n" );
                        exit( EXIT_FAILURE );
                    }
                break;
            case MENUSTATE_FISH:
                printf( "Fish menu not yet implemented, returning to main menu.\n" );
                ms = MENUSTATE_MAIN;
                break;
            case MENUSTATE_TOURNAMENT_CATCH:
                printf( "Tournament(catch) menu not yet implemented, returning to main menu.\n" );
                ms = MENUSTATE_MAIN;
                break;
            case MENUSTATE_CLOSE_TOURNAMENT:
                printf( "Close tournament not yet implemented, returning to main menu.\n" );
                ms = MENUSTATE_MAIN;
                break;
            default:
                fprintf( stderr, "unexpected error\n" );
                exit( EXIT_FAILURE );
        }
    }
}

int mainMenu( void )
{
    for (;;) //repeat forever, until input is in desired range
    {
        int option;

        option = get_int_from_user(
            "\n-------Welcome to the Fishing Tournament Main Menu!-------\n"
            "1 - Fisherman menu\n"
            "2 - Fish menu\n"
            "3 - Tournament(Catch) menu\n"
            "4 - Close Tournament (determine winner)\n"
            "5 - Quit Program\n\n"

            "Please select a menu option: "
        );

        //make sure input is in the desired range
        if ( option < 1 || option > 5 )
        {
            printf( "input must be between 1 and 5\n" );
            continue;
        }

        return option;
    }
}

int FishermanMenu()
{
    for (;;) //repeat forever, until input is in desired range
    {
        int option;

        option = get_int_from_user(
            "\n-------Fisherman Menu-------\n"
            "1 - Register fisherman\n"
            "2 - Search fisherman\n"
            "3 - Go back to main menu\n"
            "Please select a menu option: "
        );

        //make sure input is in the desired range
        if ( option < 1 || option > 3 )
        {
            printf( "input must be between 1 and 3\n" );
            continue;
        }

        return option;
    }
}

int get_int_from_user( const char *prompt )
{
    for (;;) //loop forever until user enters a valid number
    {
        char buffer[1024], *p;
        long l;

        puts( prompt );

        if ( fgets( buffer, sizeof buffer, stdin ) == NULL )
        {
            fprintf( stderr, "unrecoverable error reading from input\n" );
            exit( EXIT_FAILURE );
        }

        //make sure that entire line was read in (i.e. that
        //the buffer was not too small)
        if ( strchr( buffer, '\n' ) == NULL )
        {
            int c;

            printf("line input was too long!\n");

            //discard remainder of line
            do
            {
                c = getchar();

                if ( c == EOF)
                {
                    fprintf( stderr, "unrecoverable error reading from input\n" );
                    exit( EXIT_FAILURE );
                }

            } while ( c != '\n' );

            continue;
        }

        errno = 0;
        l = strtol( buffer, &p, 10 );

        if ( p == buffer )
        {
            printf( "error converting string to number\n" );
            continue;
        }

        if ( errno == ERANGE || l < INT_MIN || l > INT_MAX )
        {
            printf( "number out of range error\n" );
            continue;
        }

        //make sure remainder of line contains only whitespace,
        //so that input such as "12dfghoh" gets rejected
        for ( ; *p != '\0'; p++ )
        {
            if ( !isspace( (unsigned char)*p ) )
            {
                printf( "unexpected input encountered!\n" );

                //cannot use `continue` here, because that would go to
                //the next iteration of the innermost loop, but we
                //want to go to the next iteration of the outer loop
                goto next_outer_loop_iteration;
            }
        }

        return l;

next_outer_loop_iteration:
        continue;
    }
}

In the above code, I created a new function get_int_from_user, which performs extensive input validation.

Another problem is that it is not meaningful for the menu handling functions mainMenu and FishermanMenu to simply pass the number that the user entered back to the main function. It would be more meaningful for these functions to interpret and handle the input themselves.

As already suggested in the other answer, you could change the functions mainMenu and FishermanMenu to instead return the new state of the program back to main, as that would be the only information main needs, assuming that the input is interpreted and handled by the functions mainMenu and FishermanMenu.

In that case, the code of your program would instead look like this:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <limits.h>
#include <errno.h>

int mainMenu(void);
enum menu_state FishermanMenu(void);
enum menu_state get_int_from_user( const char *prompt );

enum menu_state
{
    MENUSTATE_MAIN,
    MENUSTATE_FISHERMAN,
    MENUSTATE_FISH,
    MENUSTATE_TOURNAMENT_CATCH,
    MENUSTATE_CLOSE_TOURNAMENT,
    MENUSTATE_QUIT
};

int main( void )
{
    int user_choice;

    for (;;) //loop forever until input is valid
    {
        user_choice = get_int_from_user(
            "Please select 1 to start the program or 0 to quit: "
        );

        if ( user_choice == 0 )
        {
            printf("Thank you for wasting my time! Have a great day!");
            exit( EXIT_SUCCESS );
        }

        if ( user_choice == 1 )
        {
            //input is valid, so break infinite loop
            break;
        }

        printf( "Invalid selection!\n" );
    }

    enum menu_state ms = MENUSTATE_MAIN;

    for (;;) //main program loop
    {
        switch ( ms )
        {
            case MENUSTATE_MAIN:
                ms = mainMenu();
                break;
            case MENUSTATE_FISHERMAN:
                ms = FishermanMenu();
                break;
            case MENUSTATE_FISH:
                printf( "Fish menu not yet implemented, returning to main menu.\n" );
                ms = MENUSTATE_MAIN;
                break;
            case MENUSTATE_TOURNAMENT_CATCH:
                printf( "Tournament(catch) menu not yet implemented, returning to main menu.\n" );
                ms = MENUSTATE_MAIN;
                break;
            case MENUSTATE_CLOSE_TOURNAMENT:
                printf( "Close tournament not yet implemented, returning to main menu.\n" );
                ms = MENUSTATE_MAIN;
                break;
            case MENUSTATE_QUIT:
                return;
            default:
                fprintf( stderr, "unexpected error\n" );
                exit( EXIT_FAILURE );
        }
    }
}

enum menu_state mainMenu( void )
{
    for (;;) //repeat forever, until input is in desired range
    {
        int option;

        option = get_int_from_user(
            "\n-------Welcome to the Fishing Tournament Main Menu!-------\n"
            "1 - Fisherman menu\n"
            "2 - Fish menu\n"
            "3 - Tournament(Catch) menu\n"
            "4 - Close Tournament (determine winner)\n"
            "5 - Quit Program\n\n"

            "Please select a menu option: "
        );

        switch (option)
        {
            case 1:
                printf( "opening fisherman menu\n" );
                return MENUSTATE_FISHERMAN;
            case 2:
                printf( "opening fish menu\n" );
                return MENUSTATE_FISH;
            case 3:
                printf( "opening tournament(catch) menu\n" );
                return MENUSTATE_TOURNAMENT_CATCH;
            case 4:
                printf( "opening close tournament menu\n" );
                return MENUSTATE_CLOSE_TOURNAMENT;
            case 5:
                printf( "quitting program\n" );
                return MENUSTATE_QUIT;
            default:
                printf( "input must be between 1 and 5\n" );
                continue;
        }
    }
}

enum menu_state FishermanMenu()
{
    for (;;) //repeat forever, until input is in desired range
    {
        int option;

        option = get_int_from_user(
            "\n-------Fisherman Menu-------\n"
            "1 - Register fisherman\n"
            "2 - Search fisherman\n"
            "3 - Go back to main menu\n"
            "Please select a menu option: "
        );

        switch ( option )
        {
            case 1:
                printf( "Register fisherman not yet implemented.\n" );
                return MENUSTATE_FISHERMAN;
            case 2:
                printf( "Search fisherman not yet implemented.\n" );
                return MENUSTATE_FISHERMAN;
            case 3:
                //change program state back to main menu
                return MENUSTATE_MAIN;
                break;
            default:
                printf("input must be between 1 and 3\n");
                continue;
        }
    }
}

int get_int_from_user( const char *prompt )
{
    for (;;) //loop forever until user enters a valid number
    {
        char buffer[1024], *p;
        long l;

        puts( prompt );

        if ( fgets( buffer, sizeof buffer, stdin ) == NULL )
        {
            fprintf( stderr, "unrecoverable error reading from input\n" );
            exit( EXIT_FAILURE );
        }

        //make sure that entire line was read in (i.e. that
        //the buffer was not too small)
        if ( strchr( buffer, '\n' ) == NULL )
        {
            int c;

            printf("line input was too long!\n");

            //discard remainder of line
            do
            {
                c = getchar();

                if ( c == EOF)
                {
                    fprintf( stderr, "unrecoverable error reading from input\n" );
                    exit( EXIT_FAILURE );
                }

            } while ( c != '\n' );

            continue;
        }

        errno = 0;
        l = strtol( buffer, &p, 10 );

        if ( p == buffer )
        {
            printf( "error converting string to number\n" );
            continue;
        }

        if ( errno == ERANGE || l < INT_MIN || l > INT_MAX )
        {
            printf( "number out of range error\n" );
            continue;
        }

        //make sure remainder of line contains only whitespace,
        //so that input such as "12dfghoh" gets rejected
        for ( ; *p != '\0'; p++ )
        {
            if ( !isspace( (unsigned char)*p ) )
            {
                printf( "unexpected input encountered!\n" );

                //cannot use `continue` here, because that would go to
                //the next iteration of the innermost loop, but we
                //want to go to the next iteration of the outer loop
                goto next_outer_loop_iteration;
            }
        }

        return l;

next_outer_loop_iteration:
        continue;
    }
}

On second thought, I'm not sure if my previous advice was correct. Because you seem to have a strict menu hierarchy, it may be simpler in your case not to store the state of the program in a separate variable, but to instead let the menu state be implied by the control flow of the program. In that case, your program would look like this:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <limits.h>
#include <errno.h>

void MainMenu( void );
void FishermanMenu( void );
void FishMenu( void );
void TournamentCatchMenu( void );
void CloseTournamentMenu( void );

int get_int_from_user( const char *prompt );

int main(void)
{
    int user_choice;

    for (;;) //loop forever until input is valid
    {
        user_choice = get_int_from_user(
            "Please select 1 to start the program or 0 to quit: "
        );

        if (user_choice == 0)
        {
            printf("Thank you for wasting my time! Have a great day!");
            exit(EXIT_SUCCESS);
        }

        if (user_choice == 1)
        {
            //input is valid, so break infinite loop
            break;
        }

        printf("Invalid selection!\n");
    }

    MainMenu();
}

void MainMenu(void)
{
    for (;;) //repeat forever, until input is in desired range
    {
        int option;

        option = get_int_from_user(
            "\n-------Welcome to the Fishing Tournament Main Menu!-------\n"
            "1 - Fisherman menu\n"
            "2 - Fish menu\n"
            "3 - Tournament(Catch) menu\n"
            "4 - Close Tournament (determine winner)\n"
            "5 - Quit Program\n\n"

            "Please select a menu option: "
        );

        switch (option)
        {
            case 1:
                FishermanMenu();
                break;
            case 2:
                FishMenu();
                break;
            case 3:
                TournamentCatchMenu();
                break;
            case 4:
                CloseTournamentMenu();
                break;
            case 5: 
                return;
            default:
                printf( "input must be between 1 and 5\n" );
                continue;
        }
    }
}

void FishermanMenu()
{
    for (;;) //repeat forever, until input is in desired range
    {
        int option;

        option = get_int_from_user(
            "\n-------Fisherman Menu-------\n"
            "1 - Register fisherman\n"
            "2 - Search fisherman\n"
            "3 - Go back to main menu\n"
            "Please select a menu option: "
        );

        switch (option)
        {
            case 1:
                printf( "Register fisherman not yet implemented.\n" );
                break;
            case 2:
                printf( "Search fisherman not yet implemented.\n" );
                break;
            case 3:
                printf( "Returning to main menu.\n" );
                return;
            default:
                printf( "input must be between 1 and 5\n" );
                continue;
        }
    }
}

void FishMenu()
{
    printf( "Fish Menu not yet implemented, please select another menu item.\n" );
}

void TournamentCatchMenu()
{
    printf( "Tournament(Catch) Menu not yet implemented, please select another menu item.\n" );
}

void CloseTournamentMenu()
{
    printf( "Close Tournament Menu not yet implemented, please select another menu item.\n" );
}

int get_int_from_user( const char *prompt )
{
    for (;;) //loop forever until user enters a valid number
    {
        char buffer[1024], *p;
        long l;

        puts( prompt );

        if ( fgets( buffer, sizeof buffer, stdin ) == NULL )
        {
            fprintf( stderr, "unrecoverable error reading from input\n" );
            exit( EXIT_FAILURE );
        }

        //make sure that entire line was read in (i.e. that
        //the buffer was not too small)
        if ( strchr( buffer, '\n' ) == NULL )
        {
            int c;

            printf("line input was too long!\n");

            //discard remainder of line
            do
            {
                c = getchar();

                if ( c == EOF)
                {
                    fprintf( stderr, "unrecoverable error reading from input\n" );
                    exit( EXIT_FAILURE );
                }

            } while ( c != '\n' );

            continue;
        }

        errno = 0;
        l = strtol( buffer, &p, 10 );

        if ( p == buffer )
        {
            printf( "error converting string to number\n" );
            continue;
        }

        if ( errno == ERANGE || l < INT_MIN || l > INT_MAX )
        {
            printf( "number out of range error\n" );
            continue;
        }

        //make sure remainder of line contains only whitespace,
        //so that input such as "12dfghoh" gets rejected
        for ( ; *p != '\0'; p++ )
        {
            if ( !isspace( (unsigned char)*p ) )
            {
                printf( "unexpected input encountered!\n" );

                //cannot use `continue` here, because that would go to
                //the next iteration of the innermost loop, but we
                //want to go to the next iteration of the outer loop
                goto next_outer_loop_iteration;
            }
        }

        return l;

next_outer_loop_iteration:
        continue;
    }
}

However, even if this solution is simpler and cleaner, it is not as flexible as the previous solution. If you later decide to loosen the strictness of the menu hierarchy (for example by allowing to directly jump from one menu to another menu in a completely different place in the menu hierarchy), then things would get messy very quickly.