Mumbai, July 12 :    Mumbai, July 12:  Pigs go bottom fishing - that sums up a recent trend on bourses where gullible investors are being beguiled into buying cheap, often dud, shares by operators preying on the urge to make a fast buck. Penny stocks, as they are called in the market, are peddled at the height of a rally but often turn into a worthless sheaf of paper once the stock surge peters out. Investors who missed the rally in mid-caps are looking at such bargains to make some quick money. At their peak, they would have been out of small investors' each. The penny stocks take off from where the mid caps left. Investors fall for them because they are dirt cheap and high on volumes. Crafty operators pushing these stocks into investors' portfolio do everything possible to make sure they are traded briskly and remain on the boil. That is going to change soon, though. The Securities and Exchange Board of India (Sebi) and bourses have geared up to make it difficult for operators and brokers to carry on with this game of deception. In a circular issued on Thursday, the Bombay Stock Exchange (BSE) has warned investors against companies that come out with a rash of bonus issues and whose shares are quoted at ridiculously low prices. The exchange said it is viewing with concern the rising number of announcements related to buyback and bonus issues. Members and investors have been asked to check the credentials of a firm before taking the plunge. Sebi has also made it compulsory for deals in 13 scrips to be executed on a trade-to-trade basis, meaning all transactions would have to be backed by delivery. This has sparked fears of a contraction in volumes. The measures have been announced to limit speculation and keep investors from being ambushed by operators. Moh Limited, Manna glass, Nexus, Rashil Agro, Rinki Petro, Sound Craft, Sun Info, Vatsa Education, Esatr Info, SMR Unisoft, Accurate Exports, Amtek Auto, Database Fin, Fourth Gen, Genisus Commn, Guffuc Bio and Media Matrix are among the penny stocks. Trading data for some of them have confounded experts. For instance, the Ishwar Medi scrip clocks an average a volume of 35-55 lakh every day. The likes of Transgene Biotech, which disappeared after the 2000 rally, have made a comeback; the share is clocking healthy volumes and trading at Rs 10, up from its 52-week low of Rs 2. 'It is prudent to avoid scrips of firms with unknown fundamentals,' says a fund manager affiliated to a prominent stock brokerage. The movement in penny stocks, he says, is the best indicator of how active the small investor is. The chaotic activity in most of these stocks have forced many small investors to plunge headlong into these stocks. Barring a few, most stocks in the mid and small-cap segments are no longer attractive from a short-term view, say analysts. However, every rally would witness new entrants as the stocks change hands at higher rates with the seller laughing away to the bank. The buyer, if one is lucky enough, looks for a new sucker.