Background, Aim and Scope. As Life Cycle Assessment is being increasingly applied to study fisheries and aquaculture systems, the LCA methodology must be adapted to address the unique aspects of these systems. The focus of this methodological paper is the specific allocation problems faced in studying seafood production systems and how they have been addressed to date. Main Features. The paper begins with a literature review of existing LCA research of fishing and aquaculture systems with a specific focus on 1) identifying the key allocation problems; 2) describing the choice of allocation procedures; and 3) providing insight on the rationale for those choices where available. The allocation procedures are then discussed in the context of ISO recommendations and other published guidance on allocation, followed by a discussion of the key lessons to be learned from the reviewed studies and recommendations for future LCAs of seafood production systems. Literature Review. The literature review suggests that allocation problems are most likely to arise when dealing with: landed by-catch within the context of capture fisheries, the use of co-product feed ingredients in aquaculture feeds, multiple outputs from fish farms, and the generation of by-products when seafood is processed. System expansion and allocation according to physical causality were not applied in most cases, while economic allocation was the most widely used approach. It was also observed that the level of detail and justification provided for allocation decisions in most published reports was inconsistent and incomplete. Discussion. The results of this literature review are consistent with other reviews of allocation in LCA in that allocation according to economic value was found to be the most frequently applied approach. The application of economic allocation when system expansion is not feasible is consistent with ISO guidance. However, economic allocation is not the most appropriate method in seafood production LCAs because it does not reflect the biophysical flows of material and energy between the inputs and outputs of the production system. Conclusions, Recommendations and Perspectives. More effort needs to be invested in developing allocation procedures appropriate to seafood production systems. Allocation based on gross energy content is proposed as one potential alternative means of allocating environmental burdens in some instances in seafood production LCAs. A standard set of requirements for how to describe and justify allocation decisions in published reports is needed to make these studies more robust and transparent. © 2007 ecorried publishers (Verlagsgruppe Hüthig Jehle Rehm GmbH).