What is the right minimum size for blue marlin in the Gulf Tournaments?

The Billfish Foundation newest Winthrop P. Rockefeller Ocean Program intern Nick Becker, a recent graduate from Duke University’s Nicholas School of the Environment, is working on assessing blue marlin tournaments minimum sizes on harvested blue marlin – a continuation from his master’s thesis. As a reminder, in order to be harvested, blue marlin must meet the federal size minimum of 99 inches in length. Most blue marlin tournaments have larger size minimums than the federal minimum; however, in some cases, there is still some room for improvement. Specifically, Nick’s master’s thesis, in conjunction with Dr. Grant Murray, worked on judging the size minimums in the Gulf Coast Triple Crown Tournaments and finding the best size limit for the Gulf Coast Triple Crown from a biological, economic, and social standpoint.

The Gulf Coast Triple Crown is a series of five blue marlin tournaments that take place during the summer in four different gulf coast states: Louisiana, Mississippi, Alabama, and Florida. Each state hosts one tournament, while Alabama hosts two. In these tournaments, the main goal is to catch and weigh the biggest Atlantic blue marlin. In order to be killed, a blue marlin must meet the tournament’s size minimum that is determined by length (LJFL).  Currently, most blue marlin that place 1^st, 2^nd, and 3^rd (and win money) in these tournaments generally weigh over 500 pounds.  However, the current size length minimums of 106-107 inches (101-103 inches just a couple years prior) in the Gulf Coast Triple Crown allow smaller blue marlin (in the 425 to 350-pound range) to be weighed in these tournaments. These fish rarely win any money and killing these small non-winning fish is wasting the resource. They looked at what size limit might be the most effective at preventing waste. However, these tournaments are very important from a social and economic standpoint to the Gulf Coast because each tournament generates a large amount of business and revenue for the community it is held in. Therefore, the goal of this project was to find and recommend the best size limit would be to reduce waste; that makes sense from a biological, economic, and social standpoint.

In order to determine the ideal size limit, the project analyzed catch data provided by the tournaments to examine the relationship between the weight of killed fish versus money won. The catch data is comprised of the weight of every killed blue marlin in each individual tournament, the money each killed blue marlin won (even if it was zero), the length of each killed blue marlin, and the number of boats in each tournament. The data was provided by the tournaments for each tournament going back five years. Each tournament generally has a strong, positive relationship of weight versus money won, though there are outliers. In some cases, outliers are due to ‘Calcutta’ bets. Through Calcutta bets, sometimes a boat can win money from a smaller blue marlin that does not place (meaning it isn’t 1^st, 2^nd, or 3^rd). However, on average, blue marlin that did not place in the top three places, earned significantly less than blue marlin that did place in the top three places. To determine attitudes towards current size limits and potentially raising the size limit, interviews were conducted with tournament directors, tournament fishermen, and other prominent people in the industry. A common theme was that most interviewees were in favor of raising the size limit, and that the raising of the size limit would not affect tournament participation and not precipitate negative economic impacts. This was exemplified by the Mobile Big Game Club, who moved the size minimum on killed blue marlin in their club tournaments to 110 inches last year.

Figure 1: This figure shows the relationship between the weight of a killed blue marlin versus the money each killed blue marlin won in all of the Gulf Coast Triple Crown Tournaments.

In Figure 1, the dots correspond to each killed blue marlin’s weight and prize money won; the color indicates which tournament it was killed in. The trend lines show the overall relationship of weight versus money won in each tournament. If a fish wins more money in a given tournament as its weight increases, the slope of the trendline will increase. The two tournaments with trendlines (Orange, Yellow) whose slope is not as steep, are Cajun Canyons and Orange Beach Billfish Classic. However, the reason the trendlines are not as steep is only that they are being compared against the other three tournaments. The overall payout at these two tournaments is simply smaller than at the other three, which causes the trendline to not be as steep as in the other tournaments. However, when graphed individually, the slope of the trendlines in these two tournaments is just as steep as the others. Thus, this indicates all the GCTC tournaments have a very positive relationship between weight versus money won. This indicates the bigger the fish is, the more money it is going to weigh.

After performing the analysis on the catch data from the tournaments and reviewing the findings, the project’s recommendation for a size minimum was 110 inches or 500 pounds. The Billfish Foundation sees how this work could be extended to other regions, like the South Carolina’s Governor’s Cup. The previous project with the Gulf Coast Triple Crown establishes a good baseline for tournaments and the Gulf of Mexico fishery. By extending the project to the South Carolina Governor’s Cup, this will provide another database to compare and contrast the two projects (fisheries); it also establishes a good baseline in the Atlantic fishery for those tournaments to look at and potentially use.

As of writing this, a couple tournaments like the Mississippi Gulf Coast Billfish Classic (MGCBC) recently announced that they are raising the size minimum on killed blue marlin in their tournament to 110 inches. The Director of Marketing and Promotions for the MGCBC Robbie Carter stated that the analysis, results, and overall work from this project was a contributing factor in their decision to move their size minimum up to 110 inches for future tournaments. This is incredible to see the project in action in a fishery we care so much about and at such a prestigious tournament.