Shocking Finding: Temperature and Competition Affect How Fast Fish Grow

(Figure 1)

 I'm being sarcastic if you can't hear my tone. USGS, Warmer Temperatures and Disease-Driven Population Declines Can Increase Early Life Growth Rates of Smallmouth Bass

Understanding the factors that affect growth rates of commercially and recreationally important fish species can help fisheries managers make informed stock‑assessment and fishing‑regulation decisions. In this study of smallmouth bass in Pennsylvania rivers, USGS scientists found that warmer temperatures were associated with increased early‑life growth rates, and that growth rates increased following a disease outbreak.

 

Smallmouth bass (Figure 1) are important gamefish and apex predators in the Chesapeake Bay watershed, yet few studies have assessed why their growth rates vary across locations and over time. Growth rates determine how quickly individuals can reach larger body sizes, which are typically associated with higher survival rates and greater economic benefits than smaller individuals. Numerous environmental and internal factors affect how quickly fish grow, and a lack of information about these factors makes it challenging for fisheries managers to predict how smallmouth bass populations may respond to changing watershed conditions.
 

The USGS partnered with the Pennsylvania Fish and Boat Commission to compile a 36‑year dataset (from 1986 to 2022) comprised of 54,068 individual smallmouth bass measurements collected across ten river reaches in Pennsylvania. The dataset spans a range of temperature and streamflow and includes a major disease outbreak that began in 2005. Using a von Bertalanffy growth model, researchers predicted early‑life growth rates across these different conditions and assessed the effects of temperature, streamflow, population abundance, and disease outbreak on smallmouth bass early‑life growth rates.

Major Findings

• Warmer temperatures were associated with increased early‑life growth rates, particularly for populations that did not experience any major disease outbreaks.
• A disease outbreak in 2005 was associated with a rapid increase in early‑life growth rates, likely driven by a decrease in population abundance (Figure 1B).
• Streamflow showed no significant effect on smallmouth bass early‑life growth rate.

 

The findings from this study highlight several important factors affecting early‑life growth rates of smallmouth bass. Warmer temperatures can increase early‑life growth rates; however, other studies have shown that warm waters can reduce overall body sizes. Therefore, smallmouth bass populations may grow faster but stop growing at a smaller size in warmer waters. As water temperatures warm, disease outbreaks are expected to become more frequent, and disruptive events – such as the outbreak captured in this study – could play an important role in shaping growth trajectories. Land use and similar landscape‑scale factors can also affect instream conditions and growth rates. By considering these combined influences, managers can better anticipate how population growth is expected to progress, and they can more effectively use current data to inform management strategies.

Really, you needed a study to find that? Then, of course you had to throw in global warming. 

The Wombat has Rule 5 Sunday: Oktoberfest up and garnering clicks at The Other McCain.

Chesapeake at the Crossroads - I Believe We're Sinkin' Down

A little article from USGS on the issue of how much of the problem of "rising sea level" in the Chesapeake Bay region is really a problem with sinking land, and how people do make the problem worse:

Communities of Southern Chesapeake Bay Find Sea Level Rise Heightened by Sinking Land

Communities and coastal habitats in the southern Chesapeake Bay region face increased flooding because, as seawater levels are rising in the bay, the land surface is also sinking. A new USGS report released today concludes that intensive groundwater withdrawals are a major cause of the sinking land, or 'land subsidence', that contributes to flooding risks in the region.

"From a practical viewpoint, sea level is relative to the land surface," said Jerad Bales, Acting Associate Director for Water at USGS. “Whether the water is rising or the land is sinking, or both, the effect is the same: greater vulnerability to coastal storms and loss of important coastal habitat, both of which result in economic losses."

The new study presents a variety of data and findings from previous studies to examine land subsidence in the southern Chesapeake Bay region.

Previous USGS studies have r established that the Chesapeake Bay region has the highest rates of relative sea-level rise on the East Coast. The sea-level rise rates around the Chesapeake Bay range from 3.2 to 4.7mm/per year with 4.4 mm/yr in Norfolk. (A penny is about 1 mm thick.) Land subsidence alone causes more than half of the observed relative sea-level rise in the southern Chesapeake Bay.

I like the penny analogy; I'll have to remember that one.



Wombat-Socho got the master Rule 5 Sunday post up on "Rule 5 Monday" this week. 

Remnants of Dinosaur Seas Found Under Chesapeake Bay

Oldest Large Body of Ancient Seawater Identified under Chesapeake Bay

USGS scientists have determined that high-salinity groundwater found more than 1,000 meters (0.6 mi.) deep under the Chesapeake Bay is actually remnant water from the Early Cretaceous North Atlantic Sea and is probably 100-145 million years old. This is the oldest sizeable body of seawater to be identified worldwide.

The Cretaceous Period, of course, is the era of the dinosaurs, and what good is a story about the dinosaur era without dinobabes to illustrate it?

Twice as salty as modern seawater, the ancient seawater was preserved like a prehistoric fly in amber, partly by the aid of the impact of a massive comet or meteorite that struck the area about 35 million years ago, creating Chesapeake Bay.

Interestingly, the salinity of the oceans, in the long run, is controlled  by evaporation, and formation of salts in great dry basins.

For example, much of the Mediterranean Sea is underlain by massive salt deposits left when the Med dried up during a period when it was cut off from the world ocean much like the Great Salt Lake is now.  The global ocean goes through large changes in average salinity, though over relatively long time periods.  Similar deposits around the world speaks to how common the process is geologically

"Previous evidence for temperature and salinity levels of geologic-era oceans around the globe have been estimated indirectly from various types of evidence in deep sediment cores," said Ward Sanford, a USGS research hydrologist and lead author of the investigation. "In contrast, our study identifies ancient seawater that remains in place in its geologic setting, enabling us to provide a direct estimate of its age and salinity."

 It is not inaccurate to say that the meteorite strike where the mouth of the Bay is today created the Bay as we know it.  The huge crate it blasted caused the rivers that would flow from the Appalachians to the coast to drain into the depression left.  It probably also destroyed most of the life on the east coast of North America.

The largest crater discovered in the United States, the Chesapeake Bay impact crater is one of only a few oceanic impact craters that have been documented worldwide.

About 35 million years ago a huge rock or chunk of ice traveling through space blasted a 56-mile-wide hole in the shallow ocean floor near what is now the mouth of the Chesapeake Bay. The force of the impact ejected enormous amounts of debris into the atmosphere and spawned a train of gigantic tsunamis that probably reached as far as the Blue Ridge Mountains, more than 110 miles away.

Wombat-Socho's grand compilation of Rule 5 posts,  "Rule 5 Monday: Palate Cleanser" is up at The Other McCain.

Agencies Already Making Excuses for 'Bay Diet' Fail

There are 4 different stories today in the Chesapeake Bay news feed from a new study by the USGS which shows that because of slow groundwater movement, the nutrients already stored in groundwater on the heavily agricultural Delmarva peninsula will continue to bleed into the Chesapeake Bay for decades, slowing the response of the Bay to the agricultural nutrient reductions being imposed as a result of the 'Bay Diet.'

Nutrient time lag may slow Chesapeake Bay cleansing - Delawareonline.com

Ground-water "lag" may delay Bay cleanup - B'More Green

Groundwater pushes nitrogen into Bay, delays effects of restoration - Chesapeake Bay Program

New USGS Study on Chesapeake Bay: Groundwater Delaying the Effects of Some Water Quality Actions - USGS Newsroom

I'll steal from the USGS, if only because I, like most of you, paid for these words too. Besides, their spin will be slightly less flamboyant than the EPA Bay Program's.

...Based on the concept of nitrogen mass-balance regression, the model was able to reproduce the time history of nitrate concentrations in area streams and wells, including a recent slowdown in the rate of concentration increase in streams. The model was then also used to forecast future nitrogen delivery from the Delmarva Peninsula to the Bay under different nitrogen management scenarios.

The new study shows that ages of groundwater and associated nitrogen from the Delmarva Peninsula into the Chesapeake Bay range from less than a year to centuries, with median ages ranging from 20 to 40 years. These groundwater age distributions are markedly older than previously estimated for areas west and north of the Bay, which has a median age of 10 years. The older ages occur because the porous, sandy aquifers on the Delmarva yield longer groundwater return times than the fractured-rock areas of the Bay watershed.

The USGS research found that in some areas of the Delmarva the groundwater currently discharging to streams is gradually transitioning to waters containing higher amounts of nitrate due to fertilizer used during the 1970s through the 1990s. Similarly, the total amount of nitrogen in the groundwater is continuing to rise as a result of the slow groundwater response times.

Without additional management practices being implemented, the study forecasts about a 12% increase in nitrogen loads from the Delmarva to the Bay by 2050. The study provides several scenarios for reducing nitrogen to the water table and the amount of time needed to see the reductions in groundwater discharging to streams. For example, the model predicts that a 25% reduction in the nitrogen load to the water table will be required to have a 13% reduction in load to the bay...

Which makes it sound like things are going to get worse before they get better, if they get better.  And more severe reductions will be required to make even minor improvements.  The farmers are gonna love this...