Rhetorical: Alma addresses the fallen of his congregation. The text calls those people "sheep having no shepherd." The imagery is that of a congregation that has lost its way. Of course one of the ways that the "sheep" could lose their way would be for the shepherd to be absence. Indeed, this is the image of the way that they are acting. However, this has not been the case. The shepherd has actually been there, calling. Alma specifically says: "notwithstanding a shepherd had called after you and is still calling after you, but ye will not hearken unto his voice."
Of course the Savior is the quintessential shepherd, and it is certainly appropriate to read this passage as a reference to the Savior, who has called his sheep, and who continually calls them. However, it is also possible that Alma is here referring to himself. Certainly Alma has been with his people, and in his official capacity of head of the church, he is also quite appropriately a "shepherd." It may be that Alma is reminding them of his own teachings and exhortations, the current sermon included.