Based on past experience and based on 

 Navy and Coast Guard ocean surveillance 

 functions, it is likely that a combination of 

 sensors may be required to maintain an ade- 

 quate picture of activity. When properly cor- 

 related and analyzed, information from 

 visual, radio, and radar sensors can provide a 

 picture that is much more complete and of 

 greater validity than could be provided by any 

 one or a few sensor systems. Ultimately, the 

 problems of patrolling a 200-mile fishing zone 

 may require the acquisition, correlation, and 

 analysis of multisensor data. 



The Department of Defense is the principal 

 developer and user of most of the remote- 

 sensing technology which may be applicable 

 to the fisheries enforcement problem. To a 

 lesser extent, the National Aeronautics and 

 Space Administration and the Federal Avia- 

 tion Administration are also developers and 

 users of new sensing technology. The Coast 

 Guard is now working with these other agen- 

 cies to determine what technologies would be 

 suitable and how they could be utilized in 

 fisheries enforcement. 



Transponders 



A transponder is an active beacon which 

 can be used in conjunction with radar or other 

 electronic transmission system to enhance the 

 detection and location of foreign fishing 

 vessels. The transponder transmits energy on 

 the same frequency as the radar signal, but at a 

 level several times higher than that which 

 would result from unaided reflection of the 

 signal. 



Some transponders can be hooked into 

 Loran-C receivers. Loran-C is a navigational 

 aid by which the location of a vessel is 

 automatically pinpointed by triangulation. 



using continuous signals from two shorebased 

 stations at known locations. After the location 

 is identified by Loran-C, the information is 

 passed to the transponder which retransmits 

 it, along with the vessel's identification, to a 

 control station. These systems have good 

 future potential for use in fisheries enforce- 

 ment as an extension of patrols by cutters and 

 aircraft. 



Transponders can be built that emit a stand- 

 ard, preset signal or that respond to interroga- 

 tion by a remote-sensing device by transmit- 

 ting a wide variety of identification and fish- 

 ing status information. The sophistication of 

 transponders is limited primarily by cost con- 

 siderations. However, the state-of-the-art in 

 transponders is advancing rapidly, due 

 largely to advances in digital storage and 

 processing technology, so that improved per- 

 formance at lower cost is possible in the 

 future. From a fisheries enforcement stand- 

 point, the major drawback of most transpon- 

 ders is that cooperation on the part of the 

 vessel fitted with the transponder is required. 

 A transponder that simply enhances detection 

 or supplies a preprogramed identification and 

 location signal can operate independently on 

 any input from the target, but to supply addi- 

 tional information such as fishing status or 

 catch data the vessel must provide the infor- 

 mation to be transmitted. Guaranteeing that 

 such input would be provided or that input 

 would be accurate could prove to be a serious 

 problem. In addition, since such transponders 

 could only be placed aboard vessels which 

 had permits to fish, they would do nothing in 

 identifying vessels which had illegally entered 

 an area without permit status. 



It has been suggested that in lieu of requir- 

 ing transponders on foreign fishing vessels, 

 such devices could be supplied to domestic 

 fishing craft to emit a signal that would im- 

 mediately identify them as ships with which 

 the enforcement agency need not be con- 

 cerned. 



47 



