Staging環境にデプロイしたいのですが、下記のエラーが出て動きません。

  [git][* hoge-hoge-hoge]:~/projects/hoge/ bundle exec cap stage deploy
  00:00 git:wrapper
        01 mkdir -p /tmp/hoge/
      ✔ 01 deployer@hoge.poge.me 0.226s
        Uploading /tmp/hoge/git-ssh.sh 100.0%
        02 chmod +rx /tmp/hoge/git-ssh.sh
      ✔ 02 deployer@hoge.poge.me 0.025s
  00:00 git:check
        01 git ls-remote --heads git@github.com:poge/hoge.git
        01 Permission denied (publickey).
        01 fatal: Could not read from remote repository.
        01
        01 Please make sure you have the correct access rights
        01 and the repository exists.
  (Backtrace restricted to imported tasks)
  cap aborted!
  SSHKit::Runner::ExecuteError: Exception while executing as deployer@hoge.poge.me: git exit status: 128
  git stdout: Nothing written
  git stderr: Permission denied (publickey).
  fatal: Could not read from remote repository.

  Please make sure you have the correct access rights
  and the repository exists.

  SSHKit::Command::Failed: git exit status: 128
  git stdout: Nothing written
  git stderr: Permission denied (publickey).
  fatal: Could not read from remote repository.

  Please make sure you have the correct access rights
  and the repository exists.

  Tasks: TOP => git:check
  (See full trace by running task with --trace)
  The deploy has failed with an error: Exception while executing as deployer@hoge.poge.me: git exit status: 128
  git stdout: Nothing written
  git stderr: Permission denied (publickey).
  fatal: Could not read from remote repository.

  Please make sure you have the correct access rights
  and the repository exists.

  ** DEPLOY FAILED
  ** Refer to log/capistrano.log for details. Here are the last 20 lines:

  Please make sure you have the correct access rights
  and the repository exists.
    INFO ---------------------------------------------------------------------------
    INFO START 2016-08-24 19:39:34 +0900 cap stage deploy
    INFO ---------------------------------------------------------------------------
    INFO [90de94b6] Running /usr/bin/env mkdir -p /tmp/hoge/ as deployer@hoge.poge.me
   DEBUG [90de94b6] Command: /usr/bin/env mkdir -p /tmp/hoge/
    INFO [90de94b6] Finished in 0.226 seconds with exit status 0 (successful).
   DEBUG Uploading /tmp/hoge/git-ssh.sh 0.0%
    INFO Uploading /tmp/hoge/git-ssh.sh 100.0%
    INFO [6247b79d] Running /usr/bin/env chmod +rx /tmp/hoge/git-ssh.sh as deployer@hoge.poge.me
   DEBUG [6247b79d] Command: /usr/bin/env chmod +rx /tmp/hoge/git-ssh.sh
    INFO [6247b79d] Finished in 0.025 seconds with exit status 0 (successful).
    INFO [a7f4afba] Running /usr/bin/env git ls-remote --heads git@github.com:poge/hoge.git as deployer@hoge.poge.me
   DEBUG [a7f4afba] Command: ( export GIT_ASKPASS="/bin/echo" GIT_SSH="/tmp/hoge/git-ssh.sh" ; /usr/bin/env git ls-remote --heads git@github.com:poge/hoge.git )
   DEBUG [a7f4afba]     Permission denied (publickey).
   DEBUG [a7f4afba]     fatal: Could not read from remote repository.

  Please make sure you have the correct access rights
  and the repository exists.

git ls-remoteで失敗している（Permission denied (publickey).）ようなのですが解決方法を教えてください。