In standard models of spatial harvesting, a resource is distributed over a continuous domain with an agent who may harvest everywhere all the time. For some cases though (e.g., fruits, mushrooms, algae), it is more realistic to assume that the resource is located at a fixed point within that domain so that an agent has to travel in order to be able to harvest. This creates a combined travelling–and–harvesting problem where slower travel implies a lower travelling cost and, due to a later arrival, a higher abundance of the resource at the beginning of the harvesting period; this, though, has to be traded off against less time left for harvesting, given a fixed planning horizon. Possible bounds on the controls render the problem even more intricate. We scrutinise this bioeconomic setting using a two-stage optimal control approach, and find that the agent economises on the travelling cost and thus avoids to arrive at the location of the resource too early. More specifically, the agent adjusts the travelling time so as to be able to harvest with maximum intensity at the beginning and the end of the harvesting period, but may also find it optimal to harvest at a sustainable level, where the harvesting and the growth rate of the stock coincide, in an intermediate time interval.

在空间收获的标准模型中，资源分布在一个连续的域中，并且代理商可以随时随地进行收获。但是对于某些情况（例如，水果，蘑菇，藻类），更现实的是假设资源位于该域内的固定点，因此代理必须行进才能收获。这就产生了行进和收获的综合问题，行进较慢意味着行进成本较低，而且由于到来较晚，因此在收获期开始时资源丰富。但是，在固定的计划范围内，必须以较少的收获时间为代价。控件上的可能范围使问题更加复杂。我们使用两阶段的最佳控制方法来仔细检查这种生物经济环境，并发现代理商可以节省旅行成本，从而避免过早到达资源位置。更具体地，该试剂调节行进时间，以便能够在收获期的开始和结束时以最大的强度收获，但是也可能发现最佳的以可持续水平进行收获，其中收获和生长速率在一个中间时间间隔内，库存的重合。