WI - Cormorant Research Group The Bulletin - No. 4, June 2000 Original papers

SHOOTING AND CONTROL OF GREAT CORMORANTS Phalacrocorax carbo
IN DENMARK, 1994/95-1998/99

Thomas Bregnballe & Tommy Asferg

National Environmental Research Institute, Kalø, Grenåvej 12, DK-8410 Rønde, Denmark.
E-mail: tb@dmu.dk

The increase in Great Cormorant numbers in Denmark from about 2,000 pairs in 1980 to about 29,000 pairs in 1991 brought conflicts with Danish fishermen, especially those using pound nets in fjords and coastal waters. Therefore, the Danish National Forest and Nature Agency made a conservation and management plan for the Great Cormorant in 1992. The plan, which took effect from 1 January 1993, aimed at meeting the responsibilities of having the Great Cormorant as a national responsibility species and at meeting the complaints from the fishermen, i.e. maintaining a favourable conservation status as well as reducing the damage caused by Great Cormorants. To prevent the damage caused by Great Cormorants foraging in open pound nets, professional fishermen should cover their nets with 'bird nets' or use gas cannons to scare the Great Cormorants. As a supplementary help the professional fishermen (but not non-professional fishermen) were allowed to scare away Great Cormorants by shooting individuals present within 100 m of fishing gear throughout the year. It also became legal to control Great Cormorants at fish ponds and at put and take lakes if non-lethal methods were unsuccessful. However, many fishermen continued to have problems, and consequently, from April 1997 it became legal for all owners of fishing gear (professionals as well as non-professionals) to shoot Great Cormorants within 500 m of stationary fishing gear (i.e. pound nets and fyke nets). Fishermen were, since 1993, allowed to let hunters carry out the control of Great Cormorants.

The Great Cormorant was for the first time included as a separate species in the Danish Game Bag Record in 1994/95, i.e. from the second season after fishermen were allowed to shoot Great Cormorants without dispensation. In the present paper, we use the Danish Game Bag Record to describe the temporal and geographical variations in the number of Great Cormorants shot in Denmark.

Method

Anyone wishing to practise shooting in Denmark must obtain a general shooting licence for the season (1 April - 31 March) and subsequently pass on information on their annual personal game bag to be included in the national game bag (Strandgaard & Asferg 1980). Danish hunters are known to be fairly careful in keeping their own bag record and in filling the annual questionnaire (Asferg 1996). However, there could be less precision for Great Cormorants than for other species because it appeared as a new species in the questionnaire in 1994/95 and because of the heated debate on its alleged damage to the fishery. In spite of this we suggest that the game bag record gives a fair indication of the total number and the relative geographical distribution of Great Cormorants shot in Denmark.

The Danish bag record holds information on the number of Great Cormorants bagged as totals per county. In this paper, we pooled data from neighbouring counties to describe changes within major regions in Denmark. Thus the region "North-East Sealand" includes the counties København, Frederiksborg and Roskilde; the region "West and South Sealand" includes the counties Vestsjælland and Storstrøm; the region "East Jutland" includes the counties Vejle and Århus; the region "North and West Jutland" includes the counties Ribe, Ringkøbing, Viborg and Nordjylland.

The bag record does not allow us to distinguish between Great Cormorants controlled near fishing gear and Great Cormorants shot near fish ponds, put and take lakes or elsewhere. However, the vast majority of the Great Cormorants reported to be bagged are undoubtedly Great Cormorants that were shot near fishing gear in coastal areas, and more rarely in freshwater lakes. We have no direct information on the seasonal variation in the number of Great Cormorants shot. However, recoveries in Denmark of Danish-ringed Great Cormorants suggest that most first-year birds are shot in August and September whereas most adults are shot between April and August. This is largely in accordance with what could be expected from the seasonal variation in the number of Great Cormorants in Danish waters and in the number of actively fishing pound nets and fyke nets. Professional fishermen are fishing with pound nets in both spring and autumn, whereas part-time or non-professional fishermen almost exclusively fish in late summer and autumn. Consequently, the number of nets in use increases dramatically from June to a maximum in August-October in most parts of Denmark (Bregnballe 1999). Recoveries of Danish-ringed Great Cormorants recorded drowned in fishing gear in Danish, North German and Swedish waters suggest that the overall number of Great Cormorants fishing at pound nets in Denmark is at a maximum level between July and October (Bregnballe 1999). Although professional fishermen can be expected to invest more in shooting of Great Cormorants than non-professional fishermen, we presume that most Great Cormorants are shot in late summer and early autumn. This is the period when fledged young disperse to coastal areas and freshwater lakes (Bregnballe & Rasmussen 2000) and Great Cormorants from neighbouring countries disperse to Danish waters.

Results and discussion

The bag record suggests that the total number of Great Cormorants shot in Denmark increased by 22% from 1994/95 to 1996/97 (Table 1). A small proportion of this initial increase may be explained by the inclusion of the Great Cormorant as a new species in the questionnaire in 1994/95. The overall number of Great Cormorants shot did also increase over the two subsequent seasons by 24% from 1995/96 to 1997/98 and by 16% from 1996/97 to 1998/99 (Table 1). The increase from 1995/96 to 1997/98 was mainly caused by an increase in numbers shot on Sealand (Fig. 1a) and coincides with the expansion in April 1997 of the zone around fishing gear within which shooting of Great Cormorants is legal. The number of Great Cormorants shot on Sealand subsequently dropped (Fig. 1a) and led to a decline from 1997/98 to 1998/99 in total numbers bagged (Table 1). In Jutland, bags tended to increase over most of the seasons (Fig. 1b).

Several factors may have lead to year-to-year changes in numbers shot, but there is no obvious relationship between numbers shot and the size of the local breeding populations. The intensity of fishing with pound nets has undergone rather marked changes within the period 1994-1999 (especially for professional fishermen), and we suppose that some of the changes observed in the major regions (Fig. 1) are related to changes in fishing effort. It is also likely that fishermen or those who they authorise to shoot Great Cormorants experience that shooting has an effect or has no effect and subsequently increase or decrease their effort in later seasons.


Table 1. Number of Great Cormorants bagged in Denmark during 1994/95-1998/99. Each season extends from 1 April to 31 March.

Year 1994/95 1995/96 1996/97 1997/98 1998/99
Numbers shot 2448 2982 3708 4284 3640

Fishing with pound nets and fyke nets takes place in coastal areas and freshwater lakes over most of Denmark and the bag record suggests that Great Cormorants are in conflict with pound net fishing all over the country. Overall, 43% of all Great Cormorants recorded bagged were shot on Sealand including the islands Lolland and Falster. The proportion bagged in Jutland amounted to 31% and at Funen to 26%. This distribution is largely in accordance with the relative distribution of registered pound net sites used by professional fishermen in 1994 (data from Koed & Pedersen 1995) but not in accordance with the distribution of the breeding population (Bregnballe & Gregersen 1995). We do not know the relative distribution of Great Cormorants in Danish waters outside the breeding season, but recoveries of ringed birds suggest that Sealand is an important area for Danish and foreign Great Cormorants in the post-breeding season (e.g. Bregnballe & Rasmussen 2000).

At present, we have no information about the efficiency of shooting around stationary fishing gear as a method to prevent Great Cormorants from predating or injuring fish caught in pound nets or fyke nets. Some fishermen report that regular shooting of Great Cormorants at pound nets can reduce the number of individuals appearing at their nets, whereas others have experienced no effects. It seems relevant to carry out controlled experiments in different areas and seasons to test the effectiveness of shooting as a method to reduce the damage caused by Great Cormorants at pound nets.

References

Asferg, T. 1996. Fejlkilder i den danske vildtudbyttestatistik. Report no. 167 from NERI, Kalø.

Bregnballe, T. & Gregersen, J. 1995. Development of the breeding population of Cormorant Phalacrocorax carbo sinensis in Denmark 1938-1994. - Dansk Orn. Foren. Tidsskr. 89: 119-134.

Bregnballe, T. 1999. Seasonal and geographical variation in net-entrapment of Danish Great Cormorants Phalacrocorax carbo sinensis. Dansk Ornitologisk Forenings Tidsskrift 93: 247-254.

Bregnballe, T. & Rasmussen, T. 2000. Post-breeding dispersal of Great Cormorants Phalacrocorax carbo sinensis from Danish breeding colonies. Dansk Ornitologisk Tidsskrift 94.

Koed, A. & Pedersen, M. I. 1995. Status over bundgarnsfiskeriet i Danmark 1994. Unpublished Report, Danmarks Fiskeriundersøgelser, Charlottenlund.

Strandgaard, H. & Asferg, T. 1980. The Danish bag record II. Danish Review of Game Biology 11: 1-112.

Figure 1. Number of Great Cormorants bagged on Sealand and Funen (a), and in Jutland (b) during 1994/95-1998/99. Y-axes are not drawn to the same scale.