In Borwick v Clear Water Fisheries  EWCA Civ 578, Borwick had owned and run a fishery, which consisted of nine enclosed lakes created from voids left over by the excavation of the M6, since 2005. During this time, they bought and husbanded new fish stock. In January 2016, Borwick’s lender appointed receivers to execute a charge over the land. The receivers duly sold the land to Clear Water Fisheries (CWF). The fish were not mentioned in the sale agreement and the receivers informed Borwick they did not consider them to be included under the charge. Borwick then raised an action in damages against CWF for conversion of the fish.
The case turned on issues relating to proprietary interests in ferae naturae and their application to a new factual situation. Jackson LJ referred to this as “an example of the common law searching the civil law for guidance on the true extent of property rights of this kind” . In Scotland, the Civil Law is of course the bedrock of our legal tradition. Three issues were raised on appeal: the relationship between rights acquired per industriam and ratione soli, the definition of possession for the purposes of per industriam, and whether a right held per industriam can survive the sale of the land where ferae naturae are held without their prior removal.
Rights ratione soli and per industriam
It was agreed at first instance and at the Court of Appeal that the classification of animals as ferae naturae is a matter of law, not of fact, and that fish fall within this category. This meant that the fish could not be subject to an absolute proprietary interest, but only to qualified interests. The first interest of relevance was property ratione soli, which is the exclusive right of the owner of land to take possession – and indeed to hunt or kill – any animals on their land. To put it another way, the right derives from the holder’s right to the land on which the animal can be found. The second was property per industriam, a right which arises wherever an animal is taken captive or brought under an individual’s control – that is to say, by their industry and effort. An account of this right, which many Civilian authors have followed, can be found at Inst Gai 2.67 [trans WM Gordon and OF Robinson (1998)]:
Therefore, if we should take captive any wild animal, bird, or fish, it is understood to be ours only as long as it is in our custody; for when it escapes from our control and recovers its natural liberty, it again becomes the property of the first occupant, because it ceases to be ours. It is considered to recover its natural liberty when it escapes from our vision, or, although it may be in our sight, its pursuit is difficult.
Both rights are qualified: property ratione soli ends whenever an animal passes from land owned by one person to land owned by another, while the right per industriam ends whenever an animal recovers its natural liberty and re-enters the wild. However, the court stresses that while the ratione soli is an exclusive right to reduce the animal into possession, the per industriam is an exclusive right of actual possession of an animal [15, 25]. It followed that counsel for Borwick wished to demonstrate a per industriam right to the fish, as a right held only ratione soli would naturally come to an end as soon as ownership of the land passed to CWF.
Jackson LJ and Lloyd J do not appear to have agreed on the precise relationship between these rights. Lloyd J suggests that Borwick’s rights to the fish were properly ratione soli, on the basis that “ownership [of the land] was both necessary and sufficient as the basis of [their] asserted rights” . Jackson LJ, on the other hand, considered their rights to be per industriam, “because they were so naturally associated with the purchase, introduction and cultivation of the fish, and not merely with its ownership of the land on which the lakes stood” . Jackson LJ’s view appears preferable. Rights per industriam are not residual rights to be applied only in cases where land ownership is not concerned, such as on the open sea. The essence of a right per industriam lies in the industry and effort involved in taking an animal into captivity or otherwise bringing it under one’s control. The rights which flow from individual industry co-exist with, rather than being secondary to, rights which flow from land.
Defining possession for a right per industriam
If, as Gaius states, a right per industriam requires custodia, or custody of a thing, the question is raised of what degree of control is necessary to establish this custodia. Counsel for the defendant sought to argue, based on several common law cases, that a requirement of “close control” had to be met to establish custodia. Lloyd J accepted this principle where “there is no relevant land ownership” . He referred particularly to Young v Hichens (1844) 6 QB 606, in which pilchards which had been drawn in a net at sea were disturbed by the defendant and escaped before the net could be closed. It was held in that case that possession had not yet been taken. In cases where an individual owned the land where an animal is confined, Lloyd J held that the requirement for “close control” of the animal did not apply.
Such a distinction based on the ownership of land is not satisfactory, as it introduces considerations not relevant to the scope of rights per industriam. Competing views can be found from within the Civilian tradition on the nature of the custodia required.
Discussion revolves around D 220.127.116.11-14 [ed T Mommsen and P Krueger, trans A Watson (1985)]:
 The younger Nerva says that, leaving aside a slave, movable things are possessed by us only so long as they are in our keeping, that is, so long as we can, if we so choose, take physical control of them. For once an animal strays or a vase falls, so that it cannot be found, it immediately ceases to be in our possession, even though it is possessed by no one else; this differs from the case of something which is still in our keeping, though not immediately traceable; because the fact remains that it is still there, and all that is necessary is a diligent search for it.
 Then again, we possess those wild animals which we have penned up or the fish which we have placed in tanks. But those fish which live in a lake or beasts which roam in an enclosed wood are not in our possession, because they are left in their natural state of liberty. Any other view would mean that the purchaser of a wood thereby should be held to possess all the animals in it; and that is not true.
This led Savigny to the view that not all custodia is sufficient to create rights per industriam. Rather it depends on whether the animals can be recovered according to an individual’s “mere will”, or if recover instead relies upon “a variety of accidents” [Savigny, Jus Possessionis, trans E Perry (1848), p 257]. It is of course an essential feature of a fishery lake that its fish stock cannot be recovered by “mere will”. Indeed, for many anglers, part of the enjoyment of fishing lies in the elusiveness of the catch and the challenge of snaring it.
However, Savigny’s view does not seem to have been shared by Roman-Dutch scholars. Jackson LJ, for example, cites (at ) Hugo Grotius’ discussion of D 18.104.22.168 [On the Law of War and Peace, trans FW Kelsey, ed S Neff (2012), Book II, Chapter VIII.2]:
[F]ish in a private lake are no less shut in than in a fish-pond, and well-fenced forests detain wild beasts no less effectively than parks […] these differ in no other respect than that one is a narrower, the other a less restricted confinement. Therefore in our time with greater justice the opposite opinion has prevailed, so that it is understood that we have right of ownership over wild beasts in private forests, and fish in private lakes, just as we have possession of them.
In any event, it is not clear that Savigny’s requirement for an animal to be accessible by “mere will” follows directly from the Roman text. This becomes clearer if D 22.214.171.124 and D 126.96.36.199 are read together. A thing which can be found after a search may still be considered in custodia for the purpose of establishing a right per industriam. Therefore, at least so far as the Civilian tradition is concerned, it seems that the fish in this case were under the custodia of Borwick. The rationale for this, however, lies in their ability to recover the fish if they so desired, not in their ownership of the land. This would likely be the position in Scots law.
Can a right per industriam survive the sale of land?
Having established that Borwick had a right per industriam to the fish stock, the final question is whether this right was extinguished by the sale of the land by the receivers to CWH. This is not, as Lloyd J states, an equivalent situation to inanimate chattel left on land after a sale. Property rights in inanimate chattel are absolute, while rights in ferae naturae are qualified .
Counsel for CWH relied heavily on Kearry v Pattinson  1 KB 471, in which bees held by the claimant per industriam had swarmed onto the defendant’s land, who refused permission to enter so that the swarm could be recovered. The court in that case held that the defendant was not liable for any losses as they were under no obligation to give access. Moreover, Lloyd J quotes the statement of Slesser LJ at 497 in the Kearry judgment that the claimant only kept a right per industriam to the bees “so long as they are in his sight and he has lawful power easily to pursue them” . The language of this judgment was taken indirectly from Inst Gai 2.67, via its extraction in J Inst 2.1.12 [trans P Birks and G McLeod (1987)]:
If you catch such an animal it remains yours so long as you keep it under your control. If it escapes your control and recovers its natural liberty, it ceases to be yours. The next taker can have it. It is held to have regained its natural freedom when it is out of your sight, or when, though still in sight, it is difficult for you to reach it.
Lloyd J did not consider the requirement that ferae naturae be within sight to be essential , but it is possible there has been a translation difficulty here: the Latin conspectus can refer to one’s general range of sight or perception, not necessarily to things one can see at a given moment. In any event, application of the Roman texts seem to present a challenge: the fish in this case did not at any stage and indeed could never have regained their “natural liberty”.
The key issue, however, is whether an animal remains within the custodia of whoever once exercised rights per industriam over it. The recovery of an animal’s natural liberty would be the usual consequence of a loss of custodia. The Roman jurists no doubt emphasise this because it is at the moment of natural liberty that another party can capture it for themselves.
In this case the issue simply does not arise – the fish pass out of Borwick’s custodia, not into a state of “natural liberty”, but rather immediately into the husbandry of CWH. Lloyd J notes on similar lines that what matters is whether an animal is “sufficiently in possession or not as a matter of fact” . The ability of CWH to prevent Borwick from entering their land to recover the fish terminates possession and with it the ability of Borwick to claim any further rights per industriam.
The result in Borwick v Clear Water Fisheries, as the court itself acknowledges , is harsh for Borwick, which bought and husbanded the fish stock over the course of more than a decade. However, this harshness derives not from the law on proprietary interests in ferae naturae, but rather from the circumstances of the sale. If Borwick had been involved in the sale negotiations themselves, they would no doubt have sought compensation for the fish stock; as it was, receivership took matters out of their hands. The value of the case lies in its recognition of rights per industriam as a pathway to proprietary interest that depends on the investment made by the claimant rather than merely their ownership of land – on industry rather than soil.
Jonathan Ainslie, PhD Candidate, University of Edinburgh
 A useful discussion of custodia in all its aspects can be found in M Serrano-Vicente, Custodiam praestare. La prestación de custodia en el derecho romano (2006).