On the Basking Shark Forming - Research Paper Example

?Basking Sharks: Should They Be Considered Endangered? Systematics, Distribution & Significance The basking shark is considered one of the biggest fish in Canadian waters, according to Compagno (2001). It is also the second largest and highly endangered shark species. The basking shark Cetorhinus maximus (Gunnerus, 1765) is the sole member of the family Cetorhinidae of the order of Lamniform or mackerel sharks and commonly called as the sun shark (Compagno, 2001). The most important characteristics of basking shark specified by Compagno (2001) are its long gill slits and its pointed snout, with its crescent shaped caudal fin and well-formed strong lateral keels. The color of basking shark is typically blackish to grey-brown, grey or blue-grey above and below the body and fins, often with irregular white blotches on the underside of the head and abdomen (Compagno, 2001 from COSEWIC, 2007). Basking sharks prefer cool and temperate coastal shelf waters and are distributed worldwide. In the North Atlantic (Compagno, 2001), basking sharks are sighted in waters off countries as far south and east as Senegal, through Europe, Norway, Sweden, Russia, Canada, along the eastern seaboard of the United States and into the Gulf of Mexico. In the North Pacific, they are observed as far south and west as Japan, through to China, Alaska, British Columbia, along the western seaboard of the United States and Mexico (Compagno, 2001, from COSEWIC, 2007). Habitat requirements The habitat requirements for basking shark (Sim et al, 1997) are associated with the oceanographic events on zooplankton concentration. Fronts off headlands, around islands and in bays with strong fluctuation of water masses from tidal flow were also frequented. In a study conducted by Compagno (2001), it recorded basking shark in the epipelagic zone by aerial surveys, in pelagic driftnet fisheries and is caught in bottom trawls off the St. Lawrence River, Scotian Shelf and Scotland. Te Newfoundland Observer Program (NOP) also noted that basking sharks have been caught in trawl nets fishing in depths up to 1370m. Fifteen percent of the records from waters deeper than 1000m were also observed. Skomal (2005) suggested that basking sharks migrate to different wintering habitats. They are seen to be influenced by patterns of prey distribution, varying by depths, location, and season (COSEWIC, 2007). Observed on the habitat trends of the basking sharks is the consistency of target areas and preference for high concentration of zooplankton. This has been linked to both large and small scale oceanographic conditions that change quickly (Sims and Quayle, 1998, from COSEWIC, 2007). Reproduction and Mortality The pairing of the basking shark (Sims et al, 2000) is perceived to occur in early summer. This is based on the observed courtship behavior which is nose to tail circling, and scarring. The gestation period of basking shark with a litter of six young is at 2.6 years (Pauly, 2002). The assumed length at birth is 1.5m. The time between successive litters may be two to three years (Compagno, 2001) and like other lamnoid sharks, the basking sharks develop embryonic ovophagy which supplies nutrients to the developing embryos (Compagno, 2001, from COSEWIC, 2007). The longevity of the basking shark is approximated at 50 years. The age of maturity is about 12 to 16 years in males and 16 to 20 years in females (UK CITES, 2002). Generally, females are presumed to mature at larger sizes than males with an estimated size at 4.6 to 6.1m in length at the stage of maturity. Yearly productivity ranges from 0.013 to 0.023 based on the methodology of Smith et al (1998). They used age at maturity, maximum age and average fecundity. Smith et al (1998) suggested that the potential for recovery or rebound rate may be lower for basking shark when compared to other species of Pacific sharks. Pauly (2002) determined the natural mortality to be 0.068 based on the age of maturity at 18 years for female which midrange is 16 – 20 years. The generation time calculated (Pauly, 2002) can be estimated as 18+1/0.068=33 years. In contrast to Pauly’s (2002) calculation, the UK CITES suggested (2002) that the generation time of basking sharks is 22 years. Mortality was reported from both entanglement and intentional eradication aimed to reduce the nuisance factor for salmon fishing. “Reports of four basking sharks in commercial ground fish trawl fisheries since 1996 suggests that bycatch of basking sharks has likely occurred at some level throughout the 70-year history of the trawl fleet,” (COSEWIC, 2007, 23). Population sizes and trends A disturbing report about the lack of basking shark sighted in coastal habitat suitable for the sharks was established for more than 20 years now. Only six confirmed sightings of the basking sharks were recorded in 1996, and only ten since 1973. Four out of the ten were from trawl observer records and were presumed killed. Historical records indicate a wide distribution in several areas supporting localized aggregations of about hundreds or possibly thousands (Wallace and Gisborne, 2006), but this is yet to be confirmed. The presence and concentration of basking sharks in Canada’s Pacific waters in still unknown but evidence indicates it is much reduced. There is no reliable way to estimate the current population size, according to Wallace and Gisborne (2006, from COSEWIC, 2007). Fluctuations Commercial fishery Newspaper reports support the most information on the commercial fishery for basking shark livers. In 1921, Consolidated Whaling Company described how “thousands of basking shark […] one of the coastal steamers ran into such a solid school of these big fellows that, packed tightly against the sides of the boat and around her bow, they stopped her completely” (quoted by COSEWIC, 2007, Port Alberni News, August 31, 1921). Records also show that the war-era commercial fishery for basking shark liver most probably focused on years between 1941 and 1947. The Vancouver Sun in 1946 reported “several fishboats in the Barnfield area were utilizing harpooning techniques in the pursuit for basking sharks,” (Vancouver Sun 1946 as quoted by COSEWIC, 2007). In those historical data, all basking shark landings were grouped together as “Mixed Shark”. The bulk comprised of brown cat, blue, sleeper, and salmon sharks. The years 1941 to 1945, about 379 tonnes or 841,600 pounds of mixed shark liver were reported in the annual catch summaries (COSEWIC, 2007). The newspaper records on basking shark yielded approximately 450kg or 1,000 pounds of liver and it is possible that 80 sharks may have been processed during those periods and reports. Basking sharks interactions and eradication Basking sharks for a long time were considered a threat to commercial salmon fishing operations in gillnetting and trolling. Basking sharks were observed to favor habitats similar to those of salmon. They were often encountered by salmon fishing fleets and subsequently killed to reduce interruption from salmon fishing (COSEWIC, 2007). Others died of entanglement. A photograph taken in 1901 in Rivers Inlet is an evidence of earliest verified interaction between a basking shark and the salmon gillnet fleet (BC Archives, 2004). They were seen to cause loses in thousands of dollars in salmon fishing in the Rivers Inlet district (Province, 1942). In 1943, B.C. Packers designed the “razor-billed shark slasher”, a specially fitted boat described as having “a sharp steel ram that cuts the sleeping monsters down as they lay on the surface” (Province, 1943, quoted by COSEWIC, 2007). While only six sharks were reported to have been killed by this device, subsequent reports on their perceived economic effect on salmon fishing were highlighted in Namu as reported in the Colonist (1944 from COSEWIC, 2007), damages on 100 boats fishing in Rivers Inlet reported in Province (1947 from COSEWIC, 2007). Another report indicated that thousands of basking sharks have invaded the waters in the past week were printed in Colonist (1947, from COSEWIC, 2007) but the slashing device was no longer mentioned since 1943. No reports were provided with regards to the Rivers inlet area since 1948 (COSEWIC, 2007). Anecdotal and newspaper reports suggest that basking sharks frequent the Barkley Sound region by the hundreds if not thousands from 1945 to 1969. The basking sharks were considered a nuisance to Barkley Sound gillnetters and fishermen called for eradication program from 1948 to 1954. In 1955, the Federal Fisheries Department of Canada complied with the decimation. It was reported that from 1955 to 1969, 413 sharks were killed using a large blade mounted on the bow of a fisheries patrol vessels, shooting and harpooning by patrol vessels (COSEWIC, 2007). Patrol vessels along the coast were also tasked “to opportunistically ram basking sharks” that may have helped eradicate some 200-300 (Fletcher, 2004, as quoted from COSEWIC, 2007)). Entanglement was cited as the cause for historical mortality yet there lacked evidence to substantiate this claim. Basking shark either died naturally or intentionally killed once caught in a gillnet “to salvage their nets” (Peterson, 1999, quoted by COSEWIC, 2007). Western Fisheries reported that a single gillnetter entangled seven basking sharks in a single season (November 1952, from COSEWIC, 2007). A Barkley Sound fisherman reported of “destroying” seven or eight basking sharks in a period of several years in the 1950s. It was estimated that there were approximately 150 gillnetters in Barkley Sound during attributing to the possibility of unrecorded destructions (Peterson, 1999). Other manners of death may have occurred but from 1942-1969, an estimated several hundred sharks between 400 to 500, may have been killed from entanglement in Rivers Inlet and Barkley Sound (COSEWIC, 2007). Basking shark behavior, abundance and distribution in Clayoquot Sound were observed by Darling and Keogh (1994) from 1973-1992. Based on aerial sightings and other anecdotal reports, basking sharks were seen in the Sound throughout most of the 20-year period. A photographic identification in 1992 showed 27 individuals with wounds from propellers. It was observed that the sharks were attracted to boat propellers. A few sporadic and unreported sightings since 1994 but there had been no confirmed sightings in Clayoquot Sound (Darling. 2003). Incidentally, the “disappearance coincides with the rapid development of salmon aquaculture in the region but there is no formal evidence to link these two events” (Darling, 2003, COSEWIC, 2007, 18). The Clayoquot Sound had salmon farms with large netted pens perpendicular to the coastline near areas basking sharks were common. Darling (2003) indicated that “basking sharks are easily entangled in anything, even a single line going to a prawn trap, and therefore would be vulnerable to entanglement in the net pens of a salmon farm,” (COSEWIC, 2007, 19) There were inconsistent reports from official replies of farm companies against unofficial communications from employees with regards to killed basking sharks entangled in their nets (Darling, 2005, from COSEWIC, 2007). Sport Kills It is difficult to estimate the number of basking sharks killed for sport since rare stories were published. The 1940 saw the harpooning of basking sharks that Canadian Pacific Railway promoted fishing for BC basking sharks in publicity releases (Colonist, 1953, from COSEWIC, 2007). A newspaper article cited that a person harpooned ten and landed five in a day around the Texada Island (Province, June 7, 1947, from COSEWIC, 2007). It was estimated that sport kills for basking sharks for ‘recreational’ killing and harassment led to the deaths of multiple hundreds - 50-400 (COSEWIC, 2007). Mortality and Decline The historical information on basking shark mortality is difficult to ascertain. COSEWIC (2007) reported an estimated total number of sharks killed from 1945 to 1970 by eradication to be 413, other patrol/eradication methods at 200-300, entanglement at 400-1500, and sport kills at 50-400. This is estimated at a range from 1000-2600 excluding commercial kills for liver oil (COSEWIC, 2007). Summary: Basking sharks were observed to have frequented British Columbia’s coast in numbers and distribution much larger than found today according to Wallace and Gisborne (2006, from COSEWIC, 2007). Basking sharks were also encountered by mariners in a regular manner and they had been described as plentiful and common. The disappearance of local aggregations was linked to human-caused mortality as experienced from the above discussed. Compagno (2001) have suggested that basking shark populations in annual appearance is estimated at the low thousands (COSEWIC, 2007). Occurrence of basking sharks in Clayoquot Sound was the last known aggregation in British Columbia and only very few recent surface (visual observations) or subsurface (trawl observer data) were recorded. This may mean that basking sharks are now rare in British Columbia waters. COSEWIC (2007) suggested that the population coastwide has declined dramatically from about 750 individuals to none within a span of 60 years. Basking sharks are already known to be vulnerable to human-induced mortality, aside from natural factors that contribute to their mortality: late age of maturity, low fecundity, long gestation period, long period between gestations, low productivity, sex segregated populations, use of habitat that supports commercial fisheries, lack of fear of vessels, and current small population size )COSEWIC, 2007). Human-induced mortality in Pacific Canadian waters result from encounters with fishing gears and collisions with vessels aside from being caught by trawl, entanglement in longlines, gillnets, prawn traps, cod traps, and herring seines (COSEWIC, 2007). Directed eradication program, however, impacts on decline of basking sharks observed today in Canada’s Pacific waters. Only few confirmed sightings or catches were known in recent times as only four basking sharks have been captured and presumably killed since a 100% observer coverage of the groundfish trawl fishery began in 1996 (COSEWIC, 2007). Conclusion: Basking sharks like many other natural creatures found to lack function for human consumption and enjoyment have less significance to humans, specifically to the members of the economic sector. The lack of sufficient records to indicate the existence or sustainable population of basking sharks should lead to serious consideration for inclusion in the world’s endangered species. However, there are better options to consider other than classifying creatures as either endangered or not. Humans should be educated to respect their natural environment much more than their built ones and this should extend to all natural animals, plants and other living beings. While classification of creatures for their practicality and otherwise use and un-use may be necessary to sustain a habitable ecosystem, governments should strive instead to eradicate senseless destruction of living beings unless there is sufficient danger and harm they pose to humanity and the environment. Reference: BC Archives (2004). Visual Records. Website: www.bcarchives.gov.bc.ca, Accessed May 2004 Compagno, L. (2001). Sharks of the world. An annotated and illustrated catalogue of shark species known to date. Vol. 2. Bullhead, mackerel, and carpet sharks (Heterodontiformes, Lamniformes and Orectolobiformes). FAO Species Catalogue for Fishery Purposes. No 1, Vol. 2. Roma, FAO. 269 pp. COSEWIC (2007). COSEWIC assessment and status report on the basking shark Cetorhinus maximus (Pacific population) in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. Vii + 34pp. (www.sararegistry.gc.ca/status/status_e.cfm). Darling, J.D. pers. Comm.. (2003) Telephone conversation with S. Wallace. November 2003. Pacific Wildlife Foundation, Tofino, British Columbia. Fletcher, P. pers. Comm.. (2004). Telephone conversation with S. Wallace. July 2004. Writer and previous deckhand on the patrol vessel the Laurier. Pauly, D. (2002). Growth and mortality of the basking shark Cetorhinus maximus and their implications for management of whale sharks Rhincodon typus. Pp. 199-208. In S.L. Fowler, T.M. Reed and F.A. Dipper (eds.). Elasmobranch biodiversity, conservation and management. Proceedings of the International Seminar and Workshop, Sabah, Malaysia, July 1997 IUCN SSC Shark Specialist Group, Gland, Switzerland. Peterson, J. (1999). Journeys: Down the Alberni Canal to Barkley Sound. Oolichan Books, Lantzville, British Columbia. Canada. 395 pp. Sims, D.W., Fox, A.M and Merrett, D.A. (1997). Basking shark occurrence off south-west England in relation to zooplankton abundance. Journal of Fish Biology 51:436-440 Sims, D.W., Quayle, V.A., (1998). Selective foraging behavior of basking sharks on zooplankton in a a small-scale front. Nature 393:460-464. Sims, D.W., Southall, E.J., Quayle, V.A., and Fox, A.M., (2000). Annual social behavior of basking shark associated with coastal front areas. Proceedings of the Royal Society of London. 267:1897-1904. Skomal, G.B. (2005) Basking shark tagging update. Massachusetts Division of Marine Pacific Fisheries , DMF News. Volume 25 Page. 6. Smith, S.E., Au, D., Show, C. (1998) Intrinsic rebound potentials of 26 species of Pacific sharks. Marine and Freshwater Research 49:663-678 United Kingdom. (2002). Inclusion of the basking shark (Cetorhinus maximus)on Appendix II of CITES. Conference to the Parties, Proposal 12:36. Wallace, S. and Gisborne, B. (2006). Basking Sharks:The Slaugther of BC’s Gentle Giants. Vancouver, New Star Books. 88pp. Read More