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Perspectives on Marine Environment Change in Hong Kong and Southern China, 1977-2001 (ed . B. Morton). Proceedings o f a n Internationa l Worksho p Reunio n Conference, Hon g Kong 21-26 Octobe r 2001. Hong Kong : Hong Kong University Press , 2003. THE OCCURRENCE O F SEABED DEBRIS IN HONG KONG : A COMPARISON O F CHANGES BETWEEN THE 1995 AND 2001 TRAWL SURVEY S K.F. Leung Environmental Protection Department , The Government of the Hong Kong Special Administrative Region , 28/F., Southorn Centre , 13 0 Hennessy Road, Wan Chai, Hong Kon g and Paul A . Hodgso n The Swire Institute o f Marine Science and Department of Ecology an d Biodiversity , The University o f Hong Kong, Hong Kong ABSTRACT A comparison of seabed debris collected during two trawl surveys in Hong Kong waters, one in 199 5 and th e othe r in 2001 , was made to identify an y changes i n compositio n and abundance. The most abundant seabed debris was plastic items, comprising mainly domestic an d fishin g gear . Discarde d plasti c packagin g an d fishin g gear s wer e particularly commo n i n northeaster n waters . A s compare d wit h 1995 , ther e wa s a n overall decrease in the quantity (both weight and number) of plastic packaging, such as plastic bags, in the 2001 survey. This may be related to the life span of plastic materials in the marine environment. Conversely, there was an increase in discarded fishing gea r in th e 200 1 survey . Th e explanatio n fo r suc h a n increas e ma y b e relate d t o a n intensification o f fishing activitie s and to malpractices in handling fishing gear . This is alarming because o f the ghost fishing effect s o f discarded fishing gear . The transport o f mobil e marin e debri s i n Hong Kon g water s i s als o describe d i n relation to temporal changes in the distribution of plastic bottles originating from a shipsinking incident . Th e result s showe d tha t marin e debris , i f no t entangled , coul d b e transported lon g distances ( > 35 km) across the seabed of Hong Kong. Since it is always difficult t o remove seabed debris, it is hoped that by highlighting the local situation , a n overal l reductio n ca n occu r a s a result o f better educatio n an d controls a t source. 594 K.F. LEUNG & P.A. HODGSON INTRODUCTION Marine debris is a global problem (Clark et al. 1997 ; Coe and Rogers 1997) . There are no boundaries, seemingly no limits, and far from enoug h action to restrict and mitigate such a threat to the marine environment . Regrettably, the problem of marine debris has not been assessed fully an d reported upon until recently, in particular that found o n the seabed (Coe and Rogers 1997 ; Hess et al. 1999; Moore and Allen 2000; Donhue et al. 2001). Known and potential ecological impacts of marine debris on the marine biota can be high (Coe and Rogers 1997). Much of th e composit e material s o f marin e debri s ar e plastic i n on e form o r another. Som e plastics ar e not easil y degradabl e i n the marine environmen t an d can tak e decades t o disappear (Clar k et al. 1997) . I f no t entangle d o n th e seabed , marin e debri s ca n b e mobile, tending to travel long distances and either sink somewhere in the environmen t or be washed up on beaches. The threats of marine debris match their pathways into the sea. Entanglement an d ingestion hazards have been well documented for marine animals, in particular mammals, sea turtles an d birds (Laist 1997 ; Bugoni et al. 2001). Areas with concentrated fishin g activities usually contain increased amounts of fishing debris (Pruter 1987 ; Jones 1994 , 1995; Donohue et al. 2001). Lost and discarded fishing gears are of a particular concern due t o thei r persistenc e an d abilit y t o continuously catc h an d kil l entangle d animals . This is referred t o as 'ghost-fishing ' (Smolowit z 1978 ; Carr and Harris 1997) . Benthic marine debris may also affect th e colonization and survival of sessile high conservation species, such...

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