Baltic Sea Harbour Porpoise Bibliography

Prepared for ASCOBANS by Randall R. Reeves

The following titles were judged to be relevant to the preparation of a recovery plan for harbour porpoises (Phocoena phocoena) in the Baltic Sea.

Aarefjord, H., A.J. Bjørge, C.Chr. Kinze, and I. Lindstedt.1995. Diet of harbour porpoise (Phocoena phocoena) in Scandinavian waters. Report of the International Whaling Commission (Special Issue 16):211-222.

Porpoises in Danish and Swedish waters prey mainly on gadids and clupeids, with a tendency to take benthic species more often than porpoises in Norwegian waters.

Andersen, L.W. 1993. The population structure of the harbour porpoise, Phocoena phocoena, in Danish waters and part of the North Atlantic. Marine Biology 116:1-7.

Andersen, L.W., Holm, L.-E., Siegismund, H.R., Clausen, B., Kinze, C.C., and Loeschcke, V. 1997. A combined DNA-microsatellite and isozyme analysis of the population structure of the harbour porpoise in Danish waters and West Greenland. Heredity 78:270-276.

Porpoise tissue samples from West Greenland, inner Danish waters and the North Sea were compared using microsatellite and isozyme markers. The three samples were found to represent geographically and genetically differentiated populations, but with some degree of gene flow among them. A relatively large amount of gene flow occurs between the North Sea and inner Danish waters, with the implication that this is mainly the result of male dispersal. Authors conclude that their sample from inner Danish waters ‘represents a relict of a Baltic Sea population’.

Andersen, S.H. 1982. Change in occurrence of the harbour porpoise, Phocoena phocoena, in Danish waters as illustrated by catch statistics from 1834 to 1970. Mammals in the seas, FAO Fisheries Series No. 5, Vol. IV:131-133.

Describes supposed migration of porpoises through Danish waters into and out of Baltic Sea as ‘now only a shadow of what it was,’ referring to the 19th and early 20th centuries.

Anonymous. 1997. Status of harbour porpoise in the Proper Baltic – the Polish coastal waters. Report received by the ASCOBANS Secretariat as background for the ASCOBANS Advisory Committee Meeting, 30 June-2 July 1997, Texel, The Netherlands.

Historical summary notes bounty on porpoises in Poland from early 20th century to 1935 but unclear whether catches (for the bounty) were incidental or direct, or both. Reported catch levels are used to infer that porpoises were ‘numerous’ in first third of 20th century.

Summarises ‘reports’ or ‘occurrence records’ of harbour porpoises in Polish waters from 1950s to 1996, encompassing strandings, bycatches and sightings. Highest reported bycatches were in Puck Bay and Gulf of Gdansk but there were reports from all along the coast. Salmon drift and set nets were identified as principal causes of bycatch mortality. These are generally 80-95 mm mesh nets that extend 6 m below the surface, often anchored to the bottom at one end and drifting at the other end (‘semi-drift’, typical of Puck Bay). Catches also occur in cod, flounder, pike perch and herring gill nets and at least occasionally in herring trawl nets and in set nets for other species. Fishing effort and bycatch take place mainly in winter and spring. Some porpoises are present in Polish waters in all months. Fishing effort appears most intensive in Gulf of Gdansk and adjacent waters.

ASCOBANS Advisory Committee. 1995. Report of the first meeting of the Advisory Committee, Cambridge, 8-10 March 1995.

Refers to Resolution of First Meeting of Parties calling for a sightings survey to estimate porpoise abundance in Baltic ‘as an extension of the SCANS survey’; Swedish proposal to conduct aerial survey of SW Baltic to as far north as Gotland in summer 1995.

ASCOBANS Baltic Discussion Group (ABDG). 2001. Report of the ASCOBANS Baltic Discussion Group (ABDG). Available from ASCOBANS Secretariat, Bonn. 17 pp. typescript.

Report of meeting of experts held in January 2000 to develop recommendations on research and management. Although Clarke et al. (1998) approach to assessing status is judged ‘reasonable’, there may be practical difficulties with bycatch estimation, notably in establishing an independent observer scheme and achieving necessary coverage of all relevant fisheries. Bravington’s (2000) approach to bycatch estimation could be useful if the required information were available, particularly on fishing effort and relative densities of porpoises in various geographic areas. Modelling studies were informative for the North Sea case but would not necessarily be feasible for the Baltic Sea case, because required data series (relative abundance, bycatch and fishing effort) are unavailable. Potential Biological Removal (PBR) approach mentioned (see Berggren et al. in press). Recommends that a population viability analysis (PVA) be carried out using known minimum bycatches and plausible ranges of current abundance; the purpose would be to quantify probability of extinction over short- and long-term periods under different scenarios.

Research needs: (1) Examination of available and new data to determine whether there is sub-stock structure within the Baltic and whether there is genetic and/or distributional interchange with animals to the west of the Baltic; (2) Satellite-tagging and tracking porpoises in the Baltic to determine seasonal movements and high-risk entanglement areas, improve abundance survey designs and refine stock structure hypotheses; (3) Aerial survey with greater coverage and effort than achieved in the 1995 survey (Hiby and Lovell 1996), to reduce bias and improve precision of abundance estimates; (4) Refinement of the theoretical basis for analysing acoustic data to produce, or contribute to the production of, estimates of absolute abundance; (5) Exploration of various methods of long-term monitoring the might include or incorporate, e.g. sightings data from platforms of opportunity and fixed-point acoustic monitoring devices (PODs or pop-ups); (6) Development of a ‘relative potential entanglement risk map’ based on effort-corrected distribution of high-risk fishing gear; (7) In the absence of schemes involving independent observers on-board fishing vessels, development of other approaches to obtaining reliable bycatch estimates; (8) Collation of information on existing observers schemes in certain Baltic fisheries; (9) Collection, archiving and analysis of tissue samples from Baltic porpoises, following POLLUTION 2000+ protocols; (10) Further development and testing of ‘porpoise-safe’ fishing gear and practices.

Conclusions: (1) Baltic porpoises are clearly in ‘serious’ danger; (2) Every effort should be made to reduce bycatches towards zero as quickly as possible; (3) Research that will facilitate bycatch reduction should be given highest priority; and (4) Further research is not necessary to prove the necessity of implementing management actions in fisheries where bycatches are known to occur (e.g. Swedish, German and Polish gillnet fisheries for cod and salmon). The need for effective monitoring applies all forms of management intervention. 

Berggren, P.1994. Bycatches of the harbour porpoise (Phocoena phocoena) in the Swedish Skagerrak, Kattegat and Baltic seas; 1973-1993. Report of the International Whaling Commission (Special Issue 15):211-215.

Reviews data on porpoise bycatches in Swedish coastal waters from 1973-93, allocated to three areas: Skagerrak Sea, Kattegat Sea, and Baltic Sea (using island of Saltholm as border between the latter two). Methods included search of museum records, establishment of a reward scheme for obtaining carcasses (1988-92)and establishment of reporting network with information folder (from 1992). More than 80% of bycatches for the three areas were in gill nets; in the Baltic, more than half the catches were in salmon drift nets. In the Baltic, where mean depth is 67 m, more than 75% of the documented bycatch took place in the 0-10 m depth stratum. Some catch occurred in all months, suggesting that porpoises are present in the Baltic year-round. Also cites anecdotal records suggesting that porpoises sometimes die under the ice in severe winters. Habitat degradation and pollution cited as factors that need to be considered in addition to bycatch - ‘even the low level of bycatches may be sufficient to prevent recovery. Urges that immediate efforts be made to reduce bycatch, that bycatches be estimated through a ‘scientifically designed observer program’, and that studies of abundance and stock identity be pursued.

Berggren, P. 1995. A preliminary assessment of the status of harbour porpoises (Phocoena phocoena) in the Swedish Skagerrak, Kattegat and Baltic seas. Paper SC/47/SM50 presented to the IWC Scientific Committee, May 1995. 20pp.

Berggren, P., and F. Arrhenius. 1995a. Sightings of harbour porpoises (Phocoena phocoena) in Swedish waters before 1990. Report of the International Whaling Commission (Special Issue 16):99-107.

Questionnaire survey and reports from an observer network indicate declining abundance in Swedish waters during 1960s and 1970s and continuing in late 1980s. Lack of recent sightings in Swedish Baltic waters reinforce view of Andersen (1982) that porpoises have ‘almost disappeared’ there. Factors possibly responsible: depletion of prey (e.g. herring), incidental mortality and disturbance by unspecified human activities (e.g. increased coastal boating).

Berggren, P., and F. Arrhenius. 1995b. Densities and seasonal distribution of  harbour porpoises (Phocoena phocoena) in the Swedish Skagerrak, Kattegat and Baltic seas. Report of the International Whaling Commission (Special Issue 16):109-121.

Aerial surveys resulted in only one porpoise sighting in the Baltic, leading to conclusion that although porpoises still occur in Swedish Baltic, there are no signs of recovery there.  Bycatch was considered too high for the population to sustain, and contaminants and habitat degradation ‘may also have limited the recovery potential of harbour porpoises in the Baltic Sea.’

Berggren, P., P.R. Wade, J. Carlström and A.J. Read. in press. Potential limits to anthropogenic mortality for harbour porpoises in the Baltic region. Biological Conservation.

Börjesson, P., and P. Berggren 1997. Morphometric comparisons of skulls of harbour porpoises (Phocoena phocoena) from the Baltic, Kattegat, and Skagerrak seas. Canadian Journal of Zoology 75:280-287.

Significant differences were found in skull and mandible characters between female porpoises from the Swedish Baltic Sea and those from the Swedish Kattegat and Skagerrak seas. Results of morphological comparisons support the hypothesis that porpoises migrate in winter from the Baltic Sea into the Kattegat and Skagerrak. As the morphological differences in females likely would not exist if there was interbreeding, it is proposed that Baltic and Kattegat-Skagerrak populations should be managed separately for conservation.

Bravington, M. 2000. Baltic harbour porpoise - some considerations for the Baltic Discussion Group (BDG). 4 pp.

Questions whether, in the absence of a reliable estimate of total bycatch, there is any value in having an estimate of absolute abundance of porpoises. Views low porpoise abundance as the ‘basic problem’, as it makes obtaining credible estimates of either absolute abundance or absolute bycatch extremely difficult and expensive. Concludes: ‘In the end, policy-makers and others may simply have to assume that the success or failure of mitigation measures follows the results elsewhere, and rely on non-quantitative measures of recovery or further depletion. Suggests that attempt be made to estimate net density (km-hours) by space and time (e.g. via boat-counting, interviews to establish net usage patterns, or overflight data), then overlap with relative density map of porpoise distribution in space and time, to produce an estimate of total annual bycatch rate in the Baltic. Advocates identifying and focussing mitigation efforts on ‘hotspots’ where bycatch rates are likely to be high, with caveat that population substructure within Baltic would make this a risky approach. 

If pollution is responsible for failure of Baltic porpoise population to recover, this would mean that the usually assumed 4% potential rate of increase is too high and, therefore, that the tolerable bycatch rate would have to be set lower than in the North Sea, for example.

Chappell, O.P., R. Leaper and J. Gordon. 1996. Development of an automated harbour porpoise click detector. Report of the International Whaling Commission 46:587-794.

Equipment and methodology for recording porpoise vocalizations with a hydrophone array towed by a survey vessel. Field trials resulted in detections at sufficient distances to be useful, with detection rates comparable to those achieved by an experienced team of visual observers in conditions of Beaufort sea state 3. Value in providing an index of relative abundance that is little affected by sea state and meteorological condition. Uses in addition to abundance surveys are suggested, including long-term deployment of fixed arrays to monitor presence and absence of porpoises in an area. 

Clarke, E.D., L. Hiby and S.T. Buckland. 1997. The estimation of the bycatch mortality of harbour porpoise in the Baltic Sea. ASCOBANS/MOP/2/DOC. 3 presented to the ASCOBANS Meeting of Parties, November 1997, Bonn, Germany. 49 pp.
Clarke, E.D., L. Hiby, and S.T. Buckland. 1998. The estimation of the bycatch mortality of harbour porpoise in the Baltic Sea. ASCOBANS/ADV.COMM./5/DOC. 15 presented to the ASCOBANS Advisory Committee, April 1998, Hel, Poland. 46 pp.

The 1998 version includes a few additional years of bycatch and strandings data from Germany (Table 6) and a new appendix containing an aerial survey strategy and budget; the two Clarke et al. documents are otherwise almost identical. A useful review of the history and status of harbour porpoises in the Baltic, covering information on relative abundance in different sectors, stock identity, fishing effort, bycatch recording schemes and bycatch levels. Sampling methods for an independent observer programme in the Baltic are outlined and discussed. Considers various definitions of Baltic and regions within it, and identifies preferred definitions.

Proposes approach for dealing with present situation in which best available data indicate that conservation action is required, yet the data are fraught with uncertainty and it will be difficult to evaluate effectiveness of any action taken. Concludes: ‘It seems wise ... to secure more reliable information as quickly as possible before considering closure of the fisheries. It is neither quick nor cheap to set up a full observer programme of the magnitude that would be required to ensure adequate precision on the annual bycatch estimate. By contrast, a sightings survey can be carried out relatively quickly, and relatively cheaply.’ An aerial line-transect survey is proposed as part of a 2-stage decision process. The idea is that if the central estimate and lower confidence limit of the abundance estimate were both in the order of ‘several thousand’, then there would be time to set up and obtain results from an observer programme before imposing restrictions on fishing. If the aerial survey were to yield an ‘intermediate’ result (presumably meaning high hundreds or very low thousands?), then additional bycatch information would be required ‘quite quickly’, meaning that the necessary ‘pilot’ observer programme would be ‘neither small nor cheap’. Notes difficulty (and costs) of achieving adequate precision in bycatch estimates to monitor annual removals as percentage of total population through time.

Donovan, G.P. and A. Bjørge. 1995. Harbour porpoises in the North Atlantic: edited extract from the report of the IWC Scientific Committee, Dublin 1995. Report of the International Whaling Commission (Special Issue 16):3-25.

Establishes provisional boundary between the Baltic and inner Danish and German waters using the Darss underwater ridge (between Darss, Germany, and Gedser, Denmark) and the Limhamm underwater ridge (at the inner boundary of the Oresund).  Refers to possibility of a ‘small resident Baltic population’, possibly centered in Polish waters near Gdansk (citing Skora et al. 1988). Suggests that porpoise densities are much lower in German Baltic waters than in the North Sea, citing Benke and Siebert (1995). Cites Berggren’s (1995) anecdotal evidence suggesting that porpoises were more abundant in Swedish waters in the 1960s than in the 1990s. From the same source, the northern limit of porpoises in Swedish waters is estimated to be near Gotland, and it is suggested that porpoises in Swedish Baltic waters differ from those in the Skagerrak on the basis of skull morphometrics, and from those along the Norwegian coast on the basis for mtDNA analysis, with preliminary indications that these groups can also be differentiated by comparisons of pollutant burdens. Concludes: “Although harbour porpoise abundance hs not been estimated for this area, historical records clearly indicate that the species was once much more common in the Baltic. Given the decline in abundance, the continued presence of harbour porpoises in the Baltic may be threatened.”

Gaskin, D.E. 1984. The harbour porpoise Phocoena phocoena (L.): regional populations, status, and information on direct and indirect catches. Report of the International Whaling Commission 34:569-586.

Cites literature indicating that the porpoise, ‘once considered abundant in some parts of the Baltic Sea, has decreased in numbers very significantly during the last few decades.’ Cites E. Helle (pers. comm.) opinion that porpoise is now ‘a rare animal in Finnish Baltic waters.’ Baltic population ‘may now ... rightly be regarded as a relict population well below its initial size’ and intensive net fishing in European coastal waters is likely to impede recovery. “The nature of the Baltic dictates that much of it cannot possibly function as a winter habitat for P. phocoena ....” Therefore, the population is probably strongly migratory, with most animals wintering in the ‘Danish Straits, part of the western Baltic’, or on the Great Fisher Bank. ‘The complex topography of the Baltic provides a problem in the definition of working sub-divisions’ and only two are proposed: one group in the Skagerrak, Kattegat and Danish island shelves to Gulf of Riga and Gulf of Finland; the other in the Gulf of Bothnia. Modern monofilament nets set for salmon, herring, and groundfish are viewed as greatest current threat to harbour porpoise populations.

Gordon, J. 2001. A passive acoustic survey for porpoises in the Baltic: working draft proposal. ASCOBANS Baltic Discussion Group, WP 6. 7 pp.

Describes methodology and design for a comprehensive survey of harbour porpoises in the Baltic using automated passive equipment towed behind a small, low-cost research vessel.

Gordon, J., D. Gillespie, O. Chappell, and L. Hiby. 1998. Potential uses of automated passive acoustic techniques to determine porpoise distribution and abundance in the Baltic Sea. Document submitted to 5th meeting of the ASCOBANS Advisory Committee/5/DOC. 13. 4 pp.

Acoustic detection system cited as a means of increasing efficiency, in terms of detections per unit cost, for surveys in areas such as Baltic where porpoise density is low. Issues such as determining detection probabilities, diurnal variability in detection probabilities, effective strip widths, effects of responsive behaviour by porpoises etc. are discussed.

Hammond, P.S., H. Benke, P. Berggren, D.L. Borchers, S.T. Buckland, A. Collet, M.P. Heide-Jørgensen, S. Heimlich-Boran, A.R. Hiby, M.F. Leopold and N. Øien. 1995. Distribution and abundance of the harbour porpoise and other small cetaceans in the North Sea and adjacent waters. LIFE 92-2/UK/027 report to European Commission.

Heide-Jørgensen, M.P., J. Teilmann, H. Benke, and J. Wulf. 1993. Abundance and distribution of harbour porpoises Phocoena phocoena in selected areas of the western Baltic and the North Sea. Helgoländer Meeresuntersuchungen 47:335-346.

Aerial survey results for waters immediately west of border of Baltic Sea as defined in Donovan and Bjorge (1995), i.e. for inner Danish and German waters. Data show a clear gradient in porpoise density, with densities in Bay of Kiel and the Little Belt well below those in the Great Belt and adjacent North Sea.

Hiby, L. and P. Lovell. 1996. Baltic/North Sea aerial surveys - final report. 11 pp.

Line transect aerial survey in July 1995, using same observers, equipment and methodology as in SCANS survey (see Hammond et al. 1995), covered 43,000km2 (ICES Sub-divisions 24 and 25, excluding a 22km corridor along Polish coast). Estimated abundance of 599 porpoises (CV=0.57, 95%CI 200-3,300) based on three sightings, all of them involving solitary animals. Survey by same crew in same month of Kiel-Mecklenburg Bights area produced estimate of 817 (CV=0.48, 95%CI 300-2,400). Discusses problems related to estimating abundance in situations where porpoise density and search effort are low.

This paper has been widely cited (through at least 1998) as Berggren et al. (in prep.), with authorship given as P. Berggren, H. Benke, L. Hiby and P. Hammond, and the title as ‘Harbour porpoise abundance estimates from aerial surveys in the Baltic Sea in 1995'.

IWC. 1996. Annex H. Report of the Sub-committee on Small Cetaceans. Report of the International Whaling Commission 46:160-179.

Adopted provisional definition of Baltic based on Darss and Limhamn underwater ridges (see Donovan and Bjørge, 1995). Although neither bycatch levels nor abundance had been estimated for the Baltic, ‘historical records clearly indicate that the species [harbour porpoise] was once much more common in the Baltic.’ Concluded that ‘the continued presence of harbour porpoises in the Baltic may be threatened.’

IWC. 2000. Report of the IWC-ASCOBANS Working Group on Harbour Porpoises. Journal of Cetacean Research and Management (Supplement) 2:297-305.

Kinze, C.Chr. 1985. Intraspecific variation in Baltic and North Sea harbour porpoises (Phocoena phocoena (L., 1758)). Vidensk Meddr dansk naturhist. Foren. 146:63-74.
Highly significant differences in skull characters between porpoises from ‘Baltic Sea’ and Dutch North Sea. Similarities in skull characters of porpoises from northern North Sea and ‘Baltic’ interpreted as suggesting a single continuous population in those waters. However, ‘Baltic’ sample in this study includes animals from Skagerrak and Kattegat, so difficult to evaluate differences, if any, between porpoises in these areas and those in ‘Baltic proper’.

Kinze, C.Chr. 1990. Non-metric analysis of harbour porpoise (Phocoena phocoena) from the North and Baltic seas: implications for stock identity. Unpublished paper SC/42/SM35 submitted to the Scientific Committee of the International Whaling Commission, June 1990.

Kinze, C.Chr. 1995. Exploitation of harbour porpoises (Phocoena phocoena) in Danish waters: a historical review. Report of the International Whaling Commission (Special Issue 16):141-153.

Describes directed fisheries for porpoises in Danish waters from 14th to mid-20th century. Largest catches were in Little Belt, made mainly by driving and trapping with enclosure nets. Most catching took place in the late autumn to spring months (November-May). Author suspects that a separate Baltic population would have included animals hunted in inner Danish waters, and speculates that the total population in Danish waters was in the order of 25,000. Refers to ‘bycatch along the Baltic coast line’, with capture of porpoises in large nets in southern Sweden. Directed catches in Poland are noted by citing Ropelewski (1957).

Kock, K.-H., and H. Benke. 1996. On the by-catch of harbour porpoise (Phocoena phocoena) in German fisheries in the Baltic and the North Sea. Archive of Fishery and Marine Research 44(1/2):95-114.

Describes German fisheries in Baltic and North Seas Although porpoises were entangled ‘regularly’ in salmon drift nets in the central Baltic in the 1950s and 1960s, there was no evidence of catches in this fishery in the last 10 years. Porpoises appear particularly vulnerable to sink set nets (i.e. gill and trammel nets) for cod and other gadids. Most porpoises taken incidentally in fisheries in the western Baltic have been calves (less than one year old) or subadults (older than one year but not sexually mature). Authors guess that annual German bycatch of porpoises in the ‘western Baltic’ (defined elsewhere as ‘inner German waters’) is in the order of 10-30. They emphasize that removals by German fisheries in this area are in addition to those by Danish and Swedish fisheries. They note that if porpoises in inner German waters (‘western Baltic’) are part of ‘the small population of the Central Baltic’, then ‘even low by-catches cujld have a substantial adverse effect ....’ Moreover, bycatches must be considered in context of othr potential threats (pollution and disturbance) that are ‘at present unquantifiable’.

Lindroth, A. 1962. Baltic salmon fluctuations 2: porpoise and salmon. Report of the Institute for Freshwater Research Drottningholm 44:105-112.

Määttänen, K. 1990. Occurrence of harbour porpoises (Phocoena phocoena) in Finnish waters. European Research on Cetaceans (Abstracts) 4:55-58.

Møhl-Hansen, U. 1954. Investigations on reproduction and growth of the porpoise (Phocaena phocaena (L.)) from the Baltic. Vidensk Meddr dansk naturhist. Foren. 116:369-396.

Read, A.J. 1999. Harbour porpoise Phocoena phocoena (Linnaeus, 1758). Pp. 323 in Handbook of Marine Mammals, Volume 6: The Second Book of Dolphins and the Porpoises. Academic Press, San Diego, California, USA.

Porpoises ‘were, at one time, common in the Baltic Sea, but their distribution and abundance there has been greatly reduced in recent decades (IWC, 1996).’ ‘In general, with the possible exception of the Black and Baltic Seas, incidental mortality in commercial fisheries poses the greatest current threat to harbour porpoises.’ Although organochlorine levels in tissues of porpoises in some areas ‘are high enough to warrant concern (Aguilar and Borell, 1995), ... our understanding of their effects must await more sophisticated studies of ecotoxicological risk assessment (Reijnders, 1994).’

Read, A.J. 2000. Potential mitigation measures for reducing the by-catches of small cetaceans in ASCOBANS waters. Report to ASCOBANS, December 2000. 34 pp. + appendices.

Reviews legal and regulatory framework in United States, with case studies of ‘take reduction plans’ for harbour porpoises in the Gulf of Maine and ‘Mid-Atlantic’, ‘Atlantic offshore’ cetaceans, and ‘Pacific offshore’ cetaceans. Also reviews experience in North America with various mitigation strategies, specifically acoustic alarms, time-area restrictions, modifications to fishing gear and practices, reducing fishing effort and acoustically reflective gill nets. Concludes that success depends on a clear statement of objectives, and a timetable for reaching them; meaningful (direct) involvement of stakeholders in formulating mitigation strategies; an independent observer program; using case-specific approaches involving multiple mitigation measures; and adequate means to ensure compliance (i.e. enforcement measures). Potential conflicts are noted between management objectives of ASCOBANS and national governments in the region, or the Common Fisheries Policy of Europe.

Ropelewski, A. 1957. MorÑwin (Phocoena phocoena L.). jako przylów w Polskim rybolówstwie Baltyckim. Prace Morsk. Instyt. Rybackiego Gdyni 9:427-37. [Available in English as: The common porpoise (Phocoena phocoena L.) as a by-catch in the Polish Baltic fisheries. Scientific Publications for Cooperat ion, Center of Central Institute of Scientific, Technical and Economic Information, Warsaw. 10pp. (publ. 1966).]

Summarizes statistics on porpoise bycatch in Poland, especially in surface drift gill nets for salmon. At least 54 caught per year from 1922-32, during which time there was a bounty and thus a strong incentive for fishermen to report catches. No data available for 1939-45, and no strandings or catches reported in Poland after the War until 1951, when one catch was reported. Author infers decline in porpoise abundance in Polish waters after World War II.

Rosel, P.E.

Skora, K.E. 1991. Notes on Cetacea observed in the Polish Baltic Sea., 1979-1990. Aquatic Mammals 17:67-70.

Skora, K.E., I. Pawliczka, and M. Klinowska. 1988. Observations of the harbour porpoise Phocoena phocoena on the Polish Baltic coast. Aquatic Mammals 14(3):113-119.

Fishermen report recent and current bycatch of 0-5 porpoises/yr, compared with bounty payments on 80/yr during 1922-33.

Szefer, P., M. Malinga, K. Skóra, and J. Pempkowiak. 1994. Heavy metals in harbour porpoises from Puck Bay in the Baltic Sea. Marine Pollution Bulletin 28:570-571.

Four porpoises bycaught in salmon gillnets were analysed for heavy metals in muscle, liver and kidney. Porpoises observed ‘rather more often’ since 1980 in Gda½sk Bay although still ‘a very rare species in the southern Baltic ecosystem.’

Teilmann, J., and N. Lowry. 1996. Status of the harbour porpoise (Phocoena phocoena) in Danish waters. Report of the International Whaling Commission 46:619-625.

Two stocks recognized - one in North Sea and the other in the Baltic and inner Danish waters. Reviews potential threats including, in addition to bycatch in fishing gear, pollution, ice entrapment, disturbance by vessel traffic, reduced prey abundance (e.g., herring), disease and predation (by killer whales). None of these could be entirely excluded, but all were judged secondary in importance to bycatch as likely current and ongoing causes of porpoise depletion in Danish waters.

Tiedemann, R., Harder, J., Gmeiner, C., and E. Haase. 1996. Mitochondrial DNA sequence patterns of harbour porpoises (Phocoena phocoena) from the North and the Baltic Sea. Zeitschrift für Säugetierkunde 61:104-111.

Wang, J.Y., and P. Berggren. 1997. Mitochondrial DNA analysis of harbour porpoises (Phocoena phocoena) in the Baltic Sea, the Kattegat-Skagerrak Seas and off the west coast of Norway. Marine Biology 127:531-537.

Frequency distributions of mitochondrial DNA haplotypes support recognition of a separate Baltic Sea population of porpoises. All animals sampled from the Baltic for this study were from Swedish waters between approximately 61EN and 55EN. Authors conclude that low genetic diversity of Baltic population is consistent with other lines of evidence indicating that it is severely depleted.

Wunschmann, A., U. Siebert, K. Frese, R. Weiss, C. Lockyer, M.P. Heide-Jørgensen, G. Müller and W. Baumgärtner. 2001. Evidence of infectious diseases in harbour porpoises (Phocoena phocoena) hunted in the waters of Greenland and by-caught in the German North Sea and Baltic Sea. Veterinary Record 148:715-720.

Comparisons of porpoises from Greenland and Germany revealed that the former were generally ‘healthier’ than the latter - better body condition, lower prevalence of bacterial disease and lower parasitic burdens. Concentrations of chlorinated biphenyls in blubber10 times higher in German than Greenlandic animals. Morbillivirus-specific antibody titres found in both populations.