Effects on Surveys

The NMFS Bottom Trawl Surveys remain a primary source of biological information that fisheries managers use to determine which regulatory measures to enforce. Just as we viewed the commercial cod landings in reference to the regulations that have been implemented in the last few decades, we must also look at the Surveys and the effects that regulations appear to have on them

Graph created by E. Brazer Jr.

Here we see the graph of the NMFS Surveys from 1963 to 2000. On this graph we can also see some of the major regulations that have been imposed on the fishery and their effects on the Surveys. "Averaged Spring & Fall Trawl Data" represents the spring tow data and the fall tow data averaged together to get a single annual value.

Unlike with commercial landings, TAC limits were implemented in 1973 when the Survey landed its largest catch per tow of cod in the history of the Survey. After these limits were imposed catches dropped over the next 3 years and then started to rebound. As quotas were implemented and mesh size increased, landings generally increased over the next 6 years. Once catches began to drastically decline mesh sizes were again increased. Catches continued to decline until 1986 when a Fisheries Management Plan was developed by the NEFMC. The next year the minimum legal size was increased. Catches increased between these years and continued to increase until 1988. Starting in 1989 catches drastically decreased and in 1991 began to plateau out. During the next 6 years the catches remained very low by fairly stable.

It appears that increases in minimum mesh sizes have had the largest effect on the trawl catches, similar to commercial landings. When mesh sizes were increased in 1987 commercial fishers experienced a sharp increase in landings but only for one year. In addition, mesh size increases in 1999 also resulted in landings that have been increasing steadily through fall 2002. The increased landings most likely result from the increased mesh sizes allowing a larger number of cod to escape (and reproduce) from the previous year. Despite the fact that larger numbers of cod are allowed to escape from the next, landings still increase.

In addition, the implementation of No-Take Zones and a moratorium on new groundfish permits in 1994 and 1998 also appear to have increased landings.It is still too early to determine the effects of this massive regulation implementation, however commercial landings did increase between 1999 and 2000. We may have to wait 3 or 4 years before we can determine the effects of the latest regulations and whether or not commercial landings continue to climb.[46]

Looking back over the last 4 decades it is difficult to determine exactly what the effects of the regulations has been. This is partly due to the delay in effects of the regulations. Cod that escape because of an increased minimum legal size regulation will have another year to spawn before being caught. Their offspring then won't reach a legal size for another 4 or 5 years. In addition it is near impossible to isolate the effects of a single management measure when there are multiple regulations acting simultaneously on a single population. Finally, as was mentioned before, fish populations go through natural phases where they have larger-than-normal and smaller-than-normal numbers.

During this time many regulations were imposed on the fishery including the development of new fisheries management plans, increased closure areas, increased minimum legal sizes, the prohibition of pair trawling, a moratorium on new groundfish permits, and the institution of permanent "No-Take Zones." Landings declined from 1996 through 1998 at which point two large permanent "No-Take Zones" were created. Between 1998 and 2000 catches increased by over 120%. Even though it is still too early to determine the effects of these regulations, the increased catches are a promising sign of recovery. We will still have to wait 3 or 4 years before we can determine the effects of the latest regulations and whether or not Survey landings will continue to climb.

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