Samo, Khalid

Zakaria, Mohammad Zaidi

Universiti Putra Malaysia Institutional Repository

FOR Category Fl0900: Agricultural SciencesMUL TISPECIES MANAGEMENT OF FRESHWATERFISHERIES USING MiSH SIZE REGULATIONSMohammad Zaidi Zakaria and Khalid SarnoFaculty o(Applied Sciences and TechnologyUniversiti Putra Malaysia T erengganu, Mengabang T elipot,21030 Kuala Terengganu, MalaysiaKeywords: fisheries management; multispecies fish-eries: mesh size regulation: freshwater fisheries.IntroductionMany studies have been done at Kenyir Lake for the pur-poses of obtaining the information for fisheries management(Yusoff et al. 1995; Mohammad Zaidi et al. 1997; Zakaria etal. 1998; Ambak and Jalal 1998). The mesh size regulation isan approach that have been used in fisheries management inregulating the commercial fisheries of inland waters. Theprobability of catching a fish in a gill net may be separatedinto two components: (1) the probability of the fish encoun-tering the net; and (2) the probability of the fish being caughtand retained in the net. Since the gillnets are the only gearsthat have been licensed for commercial fisheries it is impor-tant to regulate these gear. Gillnets are physically size- orspecies-selective, therefore the information could provide thebasic understanding of fish populations studies. A total of tenimportant species have been studied, i.e., Puntius schwenen-feldii, Hampala macrolepidota, Labiobarbus lineatus, Cy-clocheilichthys apagon, Osteochilus vittatus, Osteochilushasselti, Mystus nemurus, Notopterus notopterus, Chelaanomalura and pristolepis fasciatus.Materials and MethodsGillnetting experiments were conducted at Kenyir Lake fromJanuary to December 1997 in order to obtain the speciescomposition in related to their length. Seven different meshsize of gillnets were used to obtain the fish population sam-ples, which consisted of 1.5 in, 2.0 in, 2.5 in, 3.0 in, 3.5 in,4.0 in and 5.0 in. The mesh size defines a selection range, alength range of the fish vulnerable for being caught in thegillnets. Normally the smallest fish just fits in a mesh size oris slightly less. The medium-size fish is caught with the meshperimeter just around its post-operculum. Very large fish isless likely to be caught. If they are not entangled in the net,they can escape after having touched it.The cm-category in which most fish is caught is called opti-mum length (la) and is proportional to the mesh size: 10=k*m, where k is a constant specific for the fish species (slen-der fish have a higher k-value) and m refer to the mesh size.The length-at-first maturity was derived from the length-weight relationship.Results and DiscussionThere are ten to fifteen species that are commonly caught bythe gillnets. The species that we have analysed do not includethe Tor tambroides, Channa macropeltis because they areeither scarce or hardly caught using gillnets. Mystus nemurusand Hampala macrolepidota can grow more than 48 cm butthe lake were dominated by Puntius schwenenfeldii. In gen-eral, it was found that all of the fish species in Kenyir Lakewere present in the loltic habitat, while only nine specieswere found in the lentic habitat. From the lentic habitat onlytwo species were found in the littoral and open water whileseven species were found in littoral zone only. The commer-cial target species were mainly P. schwenenfeldii, and H.macrolepidota which are at present the most abundanct spe-cies found in Lake Kenyir. Other species include Tor tam-broides which can be found at certain tributaries of LakeKenyir and Channa macropelti.. which are normally caughtby hooks. It was found that the habitat partitioning of Puntiusschwenenfeldii could be grouped according to their size. Thefish smaller than 9.4 cm were normally found at the lotichabitat and the fish bigger than 9.4 cm were found at the len-tic habitat. Since the length-at-first maturity for P.schwenenfeldii was 8.6 cm, all the populations that were inthe lentic habitat were fully matured. At the lentic habitat thepopulation samples have possibly 4 cohorts with meanlengths at each cohort were 11= 9.4 cm, 12= 15.9 cm, 13=17.4 cm and 4 = 21.4 cm. However, the spawning popula-tion during migration shows that there were 5 different co-hort with the means length of each cohort was 11= 13.2cm,12= 16.5cm,13= 20.6cm,14 = 24.5cm and 15= 28.2cm.Length-at-first maturity for Hampala macrolepidota was 16cm followed sequentially by 22cm, 32 cm, 44 cm and 48 cm.However, most of the fish were caught between 11 cm to 27cm in standard length while the number bigger fish caughtwas small. This might be due to the fact that the mortalityrate was higher during this stage.ConclusionsThe commercial fisheries at Kenyir Lake mainly targetted attwo main species, that is, Hampala macrolepidota and Pun-tius schwenenfeldii. The body shape of these two species istotally different wth P. schwenenfeldii having a compressi-formes while H. macrolepidota having a torpedo shape.Based on their length-at-first maturity it is suggested that themesh size regulation can be applied for both species whichshould gives the species a chance to spawn at least once in itslife time. The mesh size of gillnets should not be less than 3inches.ReferencesAmbak, M.A. and Jalal, K.C.A. 1998. Habitat utilization by thetropical fish community in the man-made Lake Kenyir, Malaysia.Fish. Management and Ecology. 5: 173-176.Mohammad Zaidi, Z., Ku, K.Y., Kassim and Johari, M.N. 1997.Fishes of Lake Kenyir, Terengganu, collected in 1992. In: Fish-eries and the Environment: Beyond 2000. Japar Sidik, B., F.M.Yusoff, M.S. Mohd Zaki, and T. petr (eds), p. 137-141. UniversitiPutra Malaysia Serdang, Malaysia.Yusoff, F.M., Zakaria, M.Z. and Ambak, M.A. 1995. Fisheries andenvironmental management of Lake Kenyir, Malaysia. FAO Fish.Report No. 512. Suppl (FIRIJR512 Suppl.):112-128.Zakaria, M.Z., Sarno, K., Hermawan, M. and Ambak, M.A. 1998.Studies on Acoustic Target Strength of Life and Dead Puntiusschwenenfeldii at experimental tank and in situ. Journal of Octo-pus. 2(1): 42-47.Supported by JRPA Grant OJ-02-04-0172143

Multispecies management of freshwater fisheries using mesh size regulations

http://psasir.upm.edu.my/20290/1/Multispecies%20management%20of%20freshwater%20fisheries%20using%20mesh%20size%20regulations.pdf

Multispecies management of freshwater fisheries using mesh size regulations

Abstract

Similar works

Full text

Available Versions

Universiti Putra Malaysia Institutional Repository