The potential role of lobster trap bait as a significant food subsidy contributing to unprecedented recent increases in abundance and landings of the American lobster Homarus americanus is seldom considered seriously outside the fishing community. Although bait input is a very small source of organic carbon compared with primary production, the yearly input of bait per unit area to the inshore waters of the Gulf of Maine is about 85 kg/ha, an amount equal to a very productive fishery yield from a marine area. Because much of the bait is imported from outside the inshore area of the Gulf of Maine, it represents a direct subsidy to secondary production within this portion of the system. An empirical relationship between fish yield and primary production in phytoplankton-based marine systems suggests that inshore primary production would have to be increased by about 80% to provide an increment in fish yield equal to the bait input. Moreover, a simple trophic calculation based on an estimated amount of bait consumed in traps and the growth efficiency of juvenile American lobsters also shows that the bait could potentially support one-quarter to one-third of the recent American lobster landings from the inshore area of the Gulf. This preliminary assessment suggests that lobster bait may make a substantial contribution to American lobster production-a contribution that, if confirmed, should be further examined and carefully considered in future American lobster management.

Neoplasia was a prevalent disease of the soft-shell clam and was found in widely geographically distinct sites in New England. Two types of neoplasms were recognized. Most were of hematopoietic origin, except in clams from Maine, which also had gonadal neoplasms. Both types were apparently malignant neoplasms, based on their characteristic anaplastic appearance, invasiveness, metastasis, mitotic activity, associated tissue necrosis, and mortality. Diagnosis of neoplasia in the living mollusk was achieved rapidly and accurately by cytologic examination of circulating blood. The etiology of the neoplasms was not identified. In general, nonneoplastic lesions, such as epithelial hyperplasia and accumulations of a orange-brown bodies, were more common in clams from polluted areas.

Some aspects of the movements of the winter flounder Psezcdopleuronectes americanus (Walbaum) were studied by means of tag-recovery data. No gear selectivity by sex was demonstrated for recaptured fish nor was any association found between the size of the individual ancl distance of rccapturc from the release site.

Two general types of yield model, stock production and dynamic pool (yield-per-recruit), were used to analyse available data for the New Zealand rock lobster, Jasus edwardsii (Hutton). An exponential stock production model was applied to commercial catch and effort data from 1945 to 1975 for the North and South Islands combined. The results suggest a maximum sustainable yield of 4227 t with an estimated optimal level of fishing effort of 784 vessels, about 60% of the 1975 number. Empirical and von Bertalanffy growth equations were derived from limited tag-recapture data from the Gisborne area. Both equations indicate that males grow faster than females. The empirical growth equation, based on moult increment and frequency as functions of size, is considered the more realistic. Two yield-per-recruit models provided different results, especially at low levels of natural and fishing mortality. One model (Beverton-Holt) incorporated the von Bertalanffy growth equation and the other (empirical model) an empirical growth equation; the latter model is considered more realistic. The empirical model suggests that a reduction in fishing mortality below the estimated present values will not result in a substantial increase in yield-per-recruit. No strong evidence for changing the minimum size at first capture emerged from the results of the empirical model. A need is evident for more data, spanning a greater size range, to provide better estimates of growth and natural mortality, because the yield-per-recruit models were found to be sensitive to both. INTRODUCTIONThe reck lobster, Jasus edwardsii (Hutton), is of great economic significance, and is now the single most valuable renewable resource taken by the New Zealand fishing industry. The fishery began to expand rapidly with the development of export markets in the latf 1940s. The latest statistics show that about 1979 t, [valued at approximately N.Z. $23 667 000 were exported in 1977 (Anon. 1978), compared with 1799 t ^valued at N.Z. $4 619 000 in 1966. Thus, it seems prudent to develop management plans as quickly as possible to ensure sustained high productivity cf this resource and to avoid the results of over-fishing.Some information on the geographic distribution, breeding biology, and development of this species is availab , e (Kensler 1967, Sorensen 1969. Street 1970Street , 1973a has provided important information on growth, moulting, movements, reproductior, and predation, and estimates of exploitation rates from field observations and marking studies. Kenslet (1968) examined the size-fecundity relationship ofj a limited number of females.Streejt (1973a, b) described some of the management measures being used and their probable significance, but management regulations should be reexamined in the light of recent information. Since 1974 a tagging programme has been carried out by personnel of the Fisheries Research Division using the western rock lobster tag (Chittleborough 1974), which is retained through ecdysis. In addition, catch sampling, analysis of fishi...