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February 19, 2013

Bad News for Striped Bass

The past might not be a valid indicator of the future.

It is my usual rule not to write about the same subject matter two months in a row. However, I am told that rules are made to be broken.

As I write this, there is a sense that the sky is falling concerning one of recreational fishing’s most ­important ­resources. This is happening at a time when some thought we might have turned a corner and headed in a ­sustainable direction. What is the problem? It is the lowest young-of-the-year index ever recorded for striped bass in Chesapeake Bay for the 59 years this survey has been conducted. This comes a year after the ­young-of-the-year index was well above average in 2011.

The disturbingly low index — released in early October, as the figures are every year — appears to be the ­continuation of three years of decreasing numbers, all well below the long-term average of this spawning success index. These were 2008, 2009 and 2010. At the moment, fishery managers do not seem to be very concerned. To those who lived through the striped bass decline in the 1970s and ’80s, this has a very familiar feeling to it. 

Here are some of the actual numbers that provide a sense of what the 2012 index indicates. Remember, these are indices, and they give long-term trends by measuring the number of juvenile striped bass caught in haul seines employed at the same sites year after year. There are also two different indexes. One is a geometric mean and one is an arithmetic mean. Here are some of the arithmetic mean numbers: In 2012, the index was .89. The long-term average is approximately 11. The highest ever recorded was 17.61 in 1997. In 1981 — the second lowest — it was 1.22, and in 1983 it was 1.37. However, the managers are not concerned and not likely to take any radical action at this time.

Why is it that they are outwardly comfortable with where the population signs are pointing? There are a couple of important differences. In 1982, the female ­spawning stock biomass (SSB) was approximately 10 million pounds, and today it is in the ­neighborhood of 100 million pounds. These are the fish that are capable of ­producing the future generations, and the low number in 1982 was able to start a stock rebuilding that culminated in an SSB of almost 140 million pounds in 2004. The threshold that marks an overfished status is 80 million pounds. So, if a population of 10 million pounds can produce an SSB of almost 140 million pounds in 22 years, then the 100 million pound SSB should be able to maintain a population above the 80 million pound threshold. Agreed, but it still feels an awful lot like a repeat of what happened.

The next question is, why was the spawning success so low when there should have been enough spawning fish to produce at least an above-average amount of juveniles? The Maryland Department of Natural Resources points a finger at the weather conditions last spring. It seems that it was too dry in the upper reaches of the Bay with near-record-low flows. This also impacts the temperature of the water, which in our opinion is one of the ­critical components of larval survival. It should also be noted that environmental conditions on the ­spawning grounds were blamed for the downturn in the species in the late 1970s. Back then, it was too much rain that washed a high level of contaminants into the Bay that impacted the survival of the larval fish. Tongue-in-cheek, one might say we have the Goldilocks syndrome. Not too wet and not too dry, the fish need it just right. Well, truth be known, the environmental conditions are what determine the success or failure of spawning. The ­climatic aspects are the ones that we have not yet learned to control, but they are certainly as important as the condition of the SSB.

If we believe the climatologists, the weather patterns are going to be more variable in the future, and that means a greater variation from the norm. This is bound to have substantial impact on a variety of species that use ­estuarine and riverine habitats for spawning. 

While managers might have reason to believe that they have enough margin to compensate for unforeseen events, we are concerned that they are looking at past events in an effort to predict a very different future. That simply means there is a greater chance for error as species adapt to an increasingly variable environment.

Our overall track record of learning from the past is shaky at best, and that is not just a criticism of fishery ­management. The sky might not be falling just yet, but the recent spawning success, or lack thereof, will mean a number of years of lower SSB, and with all the other unknowns, we think it is a cause for concern.