Chesapeake Bay Shellfish Fisheries

Question 1

What is the highest revenue shellfish in C-Bay?

Answer 1

Blue Crab
Oysters
Sea Scallops

Question 2

Eastern Oyster Scientific Name

Answer 2

Crassostrea virginica

Question 3

Crassostrea virginica growing range

Answer 3

Canada to northern South America

Question 4

Crassastrea virginica food

Answer 4

Phytoplankton

Question 5

How do eastern oysters form reef structures?

Answer 5

Aggregate - pinpoints the importance of a hard substrate

Question 6

Eastern Oysters size and age

Answer 6

Grow to ~20 cm (larger north) and maximum age of 20-25 yrs

However, it is currently rare to find an animal over 4-5 years old. Most of the population is made up of 1-4yr olds.

Question 7

Eastern Oyster Environmental Tolerance

Answer 7

Salinity: 5 – 40 psu
Temperature: 2 - 36 ºC

Question 8

Eastern Oyster Sex and rough age of maturity

Answer 8

Protandric hermaphrodites (male first) – mature age 1.

Question 9

Eastern Oyster’s Spawning characteristics

Answer 9

Broadcast spawn
External fertilization
Spawn late spring through early fall (can spawn multiple times per season).
Female fecundity can produce up to 100 million eggs (20-30 million per spawn).

Question 10

Eastern Oyster Fishery

Answer 10

• Large fishery in 1800s through mid-1900s
• Decimated by two diseases (MSX and Dermo)

Question 11

Historical Fishing Gear Types

Answer 11

Patent tongs
Oyster dredge/oyster scrape
Hand tongs

Question 12

Scientific name for MSX

Answer 12

Haplosporidium nelsoni -

Question 13

History of MSX in the Bay

Answer 13

• Known since 1957 in Delaware Bay and 1959 in Chesapeake Bay
• Evidence suggests that Haplosporidium nelsoni was introduced to the US East coast with shipments of the Pacific oyster C. gigas

Question 14

Characteristics of MSX

Answer 14

Parasitic protist that is the agent of “MSX” disease.

An acute disease from early summer to fall (May-November), where salinities > 15 psu. Intolerant of salinities below 10 psu.

Complex life cycle unresolved. Role of oysters in life cycle isn’t clear

Question 15

The scientific name for dermo

Answer 15

Perkinsus marinus

Question 16

History of Dermo

Answer 16

• Known since the 1940s in the Gulf of Mexico and Chesapeake Bay.
• Drought occurred in the 80’s that persisted for a decade to a decade and a half increasing the salinity in ches-bay. This allowed Dermo to transit more prolifically.

Question 17

Dermo Characteristics

Answer 17

• Agent of “dermo” disease, apicomplexan protozoan or basal dinoflagellate.
• A wasting disease of the late summer and fall (August-November), salinities > 12-15 psu. However, can persist through long periods of very low salinity.
• Directly transmissible among oysters. Acquired during feeding, released upon defecation, death/disintegration.

Question 18

What is one main reason for the increase in stock in the past ten years?

Answer 18

Management has moved to rotational harvest paired with shell repletion on public grounds.

After harvesting, the beds lie fallow for two years until harvesting.

Question 19

What are some other management strategies in the oyster fishery today?

Answer 19

• Annual estimates of abundance
• License limit
• Gear type and time restrictions
• Oyster sanctuaries
• Restoration to increase the footprint of extant reefs
• Stock Management Advisory Committee
• Private Grounds
• Spat on Shell
• Increased interest in containerized aquaculture

Question 20

Characteristics of Private Grounds (leases) of Oysters

Answer 20

Traditional ”culture” methods (been in use since early 1900s)

Shell plants to catch natural set.

Seed movement from one area (often public) to the bottom is more suitable for grow-out.

Question 21

Spat on Shell

Answer 21

hatchery produced spat set on clean shell, planted on bottom for grow out then harvested by traditional methods.

Question 22

Increase in catch on Public Grounds beginning in the mid to late 2000s. Potential contributing factors?

Answer 22

• Epizootic period in mid 2000s, surviving oysters exhibiting tolerance to Perkinsus

-Increased recruitment beginning in ~2008-2010 period

-Strategy of rotational harvests implemented in 2007 (Rappahannock), other rivers in later years

Question 23

What is the biggest impediment for an increase oyster population

Answer 23

Oysters used to live to 20-25 years (need oysters to live long and die big to contribute to shell base)

-Rare to find > 4 or 5 yr old (high mortality before entering fishery – NOT fishing or disease related)

Illegal harvesting has become more prevalent in recent years with the increase in the population

Question 24

Scientific Name for Atlantic Sea Scallop

Answer 24

Plactopecten magellanicus

Question 25

Sea Scallop Biology

Answer 25

Distributed from Gulf of St. Lawrence (Canada) to Cape Hatteras

Occurs at depths from 20–120 m

Max age ~ 20 years

Max size ~ 9 inch shell height

Question 26

Sea Scallop Life Cycle

Answer 26

Planktonic (~40 days, Tº dependent)
Egg -> trochophore -> veliger -> pediveliger

Settlement
~0.25 mm shell height attach to any hard substrate with byssus threads
~5 – 12 mm shell height move to bottom debris

Question 27

How to identify between male and female sea scallops?

Answer 27

Females have red gonads

Question 28

Atlantic Sea Scallops Spawning Characteristics

Answer 28

Separate sexes

Females can mature in 1st or 2nd year w/limited egg production

Age 4 female (85–90 mm) with ~ 2 million eggs (250 million lifetime)

Spawn in fall (also a spring spawn in Mid-Atlantic)

Georges Bank gyre entrains larvae (recruitment success related to tightness of gyre)

Question 29

What factor makes it difficult to age Atlantic sea scallops?

Answer 29

Two spawning times ( on in fall and in spring)

Question 30

Sea Scallop Fishery

Answer 30

Most valuable wild scallop fishery in the world

Most valuable fishery in Virginia (more recent years toss-up with oysters)

In 2007, the most valuable single species in the U.S.
58.5 million lbs. landed (~2.3 million lbs landed in 2021)
$385 million ex-vessel

Question 31

What is the main gear type for Atlantic Scallop Fishery?

Answer 31

Scallop Dredge

Question 32

Scallop Fishery Management

Answer 32

limited access program implemented

Effort reductions (days at sea)

Limitations on crew size

Gear restrictions (increase in cull ring size 3.0” -> 3.25” -> 3.5” -> 4.0”)

Georges Bank Groundfish Closure 1993-1999

Question 33

Georges Bank Groundfish Area Closure

Answer 33

Groundfish was being overfished and completely closed the fishery. They found that the animals in the large-scale classes were still not there outside the closure area. Within the closure area, they were finding the larger size classes. This led to the rotational grazing practice that is now implemented with the oyster fishery in Ches-bay.

Question 34

What are some unique features of the scallop industry that differ from other shellfish fisheries?

Answer 34

puts a certain amount of money into a pot every year to provide money for researchers. To help them make informed decisions.

Scallop fisheries – all vessels have vessel monitoring systems. Must have them turned on when they leave the dock.

The fishery (in terms of the big players) the fishery is much smaller. Easier to mange.

Question 35

Scientific Name for Blue Crab

Answer 35

Callinectes sapidus

Question 36

Blue Crab Biology

Answer 36

Range throughout western Atlantic (Nova Scotia to Argentina)

Tolerate wide range of temperatures, prefer estuarine salinities

Adult blue crab diet includes bivalves (hard clams, oysters), fish, crabs (including blue crabs), shrimp, plant matter, detritus, etc

Important prey & predator in the Bay

Relatively short lived: females to ~2 years, males to ~3 years

Question 37

Blue Crab Spawning Characteristics

Answer 37

Mating occurs May to Oct in brackish water (upper Bay) when female soft (final molt)

Males protect females, but females can have multiple mates (Wells et al. 2017)

Females store spermatophore

Females produce ~1,000,000 – 5,000,000 eggs/spawn

Females move toward mouth of Bay

If late in the season, ovulation will be delayed until following spring

Crabs bury into sand and are dormant during winter

Question 38

Blue Crab Fishery

Answer 38

Chesapeake Bay with ~1/3 of U.S. blue crab catch
Pot fishery (typically March-November)
Winter Dredge fishery (current moratorium)
Peeler crab/soft shelled crab fishery
Recreational fishery
Estimated to be 8% of total harvest (male only in MD)

Question 39

Blue Crab Spawning Sanctuary

Answer 39

Most of c-bay is closed may 16-sept 15 for recreational and commercial harvest

Small portion of the mouth of C-bay and along the Atlantic coast is closed from may 16- sept 15 for commercial harvest

Question 40

Blue Crab Stock Challenges

Answer 40

Since 45-55% of crabs are harvested annually – causes issues in the population.

Temp increase – lose more SAV

Dead zones (loss of food)

Question 41

Blue Crab Management (Chesapeake Bay Stock Assessment Committee)

Answer 41

CBSAC uses winter dredge survey as primary indicator of stock status

2011 assessment implements management targets focused on the number of spawning age (1+) females as opposed to total number of crabs

2011 w/ highest total number of crabs since 1990s

2015 - started to manage the fishery based on female abundance

2017 set new (updated) biological reference points

Question 42

Blue Crab Stock Status

Answer 42

In 2022 abundance of both mature male and females decreased and juvenile abundance remained low.
2022 results suggest that the blue crab stock is not overfished.
However, the reduced abundances, low recruitment and higher male exploitation rates are of concern.