| FAO Fisheries Synopsis No.99 | FRm/S99 SAST - Shrimp |
prepared by
W.A. DAHLSTROM
The Resources Agency of California
Department of Fish and Game
Marine Resources Operations
Menlo Park, California 94025, U.S.A.
Pandalus jordani Rathbun, 1902, Proc.U.S. Nat.Mus., 24:900.
None.
Suprageneric
Phylum Arthropoda
Class Crustacea
Subclass Malacostraca
Series Eumalacostraca
Superorder Eucarida
Order Decapoda
Suborder Natantia
Section Caridea
Family Pandalidae
Generic
Pandalus Leach, 1814, Brewster's Edinburgh Encyclopaedia, 7:432. Gender masculine. Type species, by monotypy: Pandalus montagui Leach, 1814.
The generic concept as used by Holthuis (1955) has been adopted. The following definition of the genus Pandalus is based on his ‘Key to the Pandalidae’.
Carpus of 2nd pereiopods consisting of more than 3 joints. No longitudinal carinae on the carapace except the postrostral crest. Rostrum not movable. Eyes well developed, cornea much wider than eyestalk. Third maxilliped without exopod. Laminar expansion of the inner border of the ischium of the 1st pair of pereiopods wanting or inconspicuous. The first 4 pereiopods with epipods. Arthrobranchs present at the bases of the first 4 pereiopods. Posterior lobe of scaphognathite acutely produced. Upper margin rostrum with movable spines only.
Rathbun (1904) listed the following species from the northwest coast of North America: Pandalus borealis Krøyer, P. goniurus Stimpson, P. jordani Rathbun, P. leptocerus Smith, P. montagui tridens Rathbun, P. platyceros Brandt, P. hypsinotus Brandt, P. gurneyi Stimpson, P. stenolepis Rathbun and P. danae Stimpson. Of these species, P. leptocerus has an exopodite on the 3rd maxilliped and is consequently included in the genus Dichelopandalus Caullery by many authors.
Specific
Pandalus jordani Rathbun, 1902.
Identity of type specimen. The type specimens are preserved in the collection of the U.S. National Museum, Washington D.C. (Cat.No. 252 77).
Type locality: “Off Santa Cruz Island, California, 155 fathoms” (Rathbun, 1902).
Rathbun (1902) gave the following diagnosis of the species: "Surface smooth and shining. Rostrum about one and three fourthstimes as long as carapace, slightly arched above the eyes, terminal two thirds ascending; slender, armed with 14 to 17 spines above, including 4 on the carapace; distal three immovable, others movable; closer together above the eye; 7 to 10 immovable spines below, extending nearer to tip than superior spines; tip acuminate; the posterior of the dorsal spines lies between the middle and the anterior third of the carapace.
"Antennal spine strong; pterygostomian small, slender. Eyes large, pyriform.
"Peduncle of antennulae reaching to middle of antennal scale; second and third joints subequal; flagella subequal, one and a half times as long as carapace, thickened portion of outer flagellum extending half its length beyond the antennal scale. Scale three fourths to four fifths as long as carapace, extremity of blade broadly rounded, and equally produced with the spine; antennal peduncle reaching to end of second segment of antennular peduncle; flagellum one fourth longer than body.
"Outer maxillipeds slender, not reaching end of acicle. First pair of feet a little shorter; of the second pair, the right foot extends about to end of scale, the left may be half again as long; the right carpus has 19 to 22 segments, the left 58 to 63 segments. The last three pairs of feet diminish a little in length successively, the third pair exceeding the scale slightly; their dactyli are elongate, and are contained from two and a half to two and four fifths times in their propodi.
“The third segment of the abdomen is compressed and its posterior half carinated, the carina interrupted by a slight lobe at the posterior third of the segment; this lobe is of varying size, at no time strong, and having a tendency to disappear in large specimens, where it may occur only as a slight unevenness in the curve seen in profile; posterior margin well produced backward, rounded, unarmed; fourth segment with posterior margin truncate, entire; sixth about twice as long as fifth and three fourths as long as seventh, which has 10 to 13 lateral aculei on each side.”
For an illustration of the species see Fig. 1.
Fig. 1 Pandalus jordani Rathbun. From top to bottom: 1, 2 and 3 yr old specimens. Scale in inches. (Photograph by W.A. Dahlstrom)
Subjective synonymy
None
Artificial key to the species of Pandalus (including Dichelopandalus) from the north-eastern Pacific (Rathbun, 1904).
A' Third segment of abdomen in part compressed and carinated, forming a more or less well defined lobe or spine in front of posterior margin.
B. Third and 4th segments of abdomen armed with a median spine on posterior margin. P. borealis
B'. Third and 4th segments of abdomen without median spine on posterior margin.
C. Rostrum unarmed on distal half of superior margin. P. goniurus
C'. Rostrum with spines on distal half of superior margin. P. jordani
A'. Third segment of abdomen not compressed and carinated, and without a median lobe or spine in front of posterior margin.
B. Dorsal spines not reaching behind middle of carapace.
C. Sixth abdominal segment more than twice as long as wide.
D. Carapace and abdomen covered with short transverse rugose lines. P. leptocerus
D'. Carapace and abdomen smooth. P. montagui tridens
C'. Sixth abdominal segment less than twice as long as wide. P. platyceros
B'. Dorsal spines extending behind middle of carapace.
C. Dorsal spines more than 15(17 – 21) P. hypsinotus
C'. Dorsal spines less than 15
D. Rostrum 1 ½ or more than 1 ½ times as long as carapace. P. gurneyi
D'. Rostrum less than 1 ½ times as long as carapace.
E. Antennal scale very narrow, the terminal half of the blade narrower than the adjacent thickened portion. P. stenolepis
E'. Antennal scale of moderate width, the terminal half of the blade not narrower than the adjacent thickened portion. P. danae
The species is distinct from its several congeners and is recognized by all specialists as a valid species.
No subspecies have been described.
The name sanctioned by the State of California for purposes of record keeping is ocean shrimp. Other names are pink shrimp, ocean pink shrimp, and smooth pink shrimp.
No individual or geographic variations in external morphology have been reported. During growth, the structure of the pleopods alters in specimens which change sex from male to female (see section 3.11).
The species ranges from Unalaska to San Diego, California, at depths of 36 to 457 m and is usually found over a green mud, or mixed mud and sand bottom. In terms of the FAO areas code (given by Holthuis and Rosa, 1965) the distribution is in sea areas INE and ISE and off land areas 212, 220, 231 and 232.
The population appears to have its maximum density off central Oregon, but is also abundant in waters from northern California to at least Cape Beale, Vancouver Island. The highest catch rates occur off the Oregon and Washington coasts at depths of 110 to 183 m (Ronholt, 1963). Commercial concentrations off California are generally found in 110 to 146 m. P. jordani, the dominant species in Washington, Oregon, and California waters, is largely replaced by P. borealis in waters off British Columbia and Alaska, the transition occurring off British Columbia.
Bottom temperatures on California shrimp beds have been recorded from 7.1 to 11.5°C during March and October, 1962 and 1963. Bottom water salinities during April 1963 and April 1964 ranged from 33.04 to 34.64‰ (Dahlstrom, unpublished data). Alverson, NcNeely and Johnson (1960) reported bottom temperatures over the Washington-Oregon shrimp beds ranging from 5.6 to 8.2°C. Butler (1964) reported a temperature range of 7.44 to 10.97°C, and a salinity range of 28.69 to 30.83‰ for shrimp beds in British Columbia.
The larvae are believed to be pelagic. Berkeley (1930) studied the development of several other species of Pandalus in waters off British Columbia. She found no pandalid larvae at the surface, larvae in the first 2 stages showed a fairly even vertical distribution, and later stages were found near the bottom. She observed no general coastwise migration during larval development.
Usually, juveniles tend to occur in shallower water than adults, but juveniles can be found intermixed with adults over a considerable area within the shrimp bed.
During the first 6 mo of each year, males, which are younger than the majority of females, tend to occupy relatively shallow waters (generally 75 to 128 m) and females are found at greater depths. In the second half of the year there is a general mixing of the adult year-classes and a larger portion of the population is female, due to sex change.
Fishable concentrations are discontinuous along the coasts of Washington, Oregon, and California, and the fisheries are generally located in the same areas each year. The populations appear to be stable and do not shift north or south out of the known shrimp beds. Many areas along the coast, exhibiting the same green-mud substrate, temperatures and salinities as the shrimp beds, are devoid of ocean shrimp.
Ocean shrimp are, for the most part, protandric hermaphrodites. The normal pattern is for an individual to mature and function as a male during the 2nd or 3rd yr of life and then change sex, mature, and function as a female. However, deviations from this normal pattern have been noted with the appearance of primary females (non-hermaphroditic) during the 2nd yr of life. These females, which become sexually mature in their 2nd yr, are devoid of all traces of male characters. In British Columbia, over 40 percent of mature females in the 2nd-yr group are estimated to be primary females (Butler, 1964). In California during certain years, many primary females can be found in the 2nd-yr group. Primary females constituted as much as 77 percent of the 2nd-yr group and up to 68 percent of the whole shrimp population off Bodega Bay, California, in 1965. The extent of hermaphroditism appears to depend on the region and the numbers of the 2nd-yr group in the population. There is evidence to indicate that hermaphroditism is more common among pandalids living in the optimum sections of their geographical ranges and in deeper water species, and that the occurrence of non-hermaphroditic females is associated with populations near the limits of distribution of the species or in shallow water (Butler, 1964).
The sexes of P. jordani can easily be distinguished by certain external structures on the 1st and 2nd pleopods. The development and changes in the pleopods are as follows (Rubtzoff, in press): The endopodite of the 1st pleopod in an immature shrimp (2 to 3 mo old) does not have any sexual characteristics (Fig. 2a). As the shrimp starts its development as a male, the so-called organ of copulation begins to develop on the endopodite (Fig. 2b to e). Its tip is covered with small hooks called cincinnuli. Finally, full development of the endopodite is reached in the mature male (Fig. 2f1). The degeneration of the organ of copulation and simultaneous elongation of the tip of the endopodite accompany the change of sex (Fig. 2g1 to i1). When the female reaches maturity, the organ of copulation is lacking entirely (Fig. 2j1). (In the figures the bristles, hairs, and cincinnuli are omitted.)
The endopodite of the 2nd pleopod in the male bears an appendix masculina in the axil of the appendix interna (Fig. 3). An appendix interna is found on each of the 2nd to 5th pleopode of both sexes. The appendix masculina is found only on the 2nd pleopod of the male. It is lacking in young animale, but it starts to develop as a small rounded projection (Fig. 3c), which then elongates. Simultaneously, bristles begin to appear on or near its tip. They are at first small and few in number, but as the appendage grows they become larger and more numerous (Fig. 3d and e) until the condition in a mature male is obtained (Fig. 3f1). A gradual disappearance of the appendix masculina accompanies the change of sex (Fig. 3g1 to i1, and f2 to i2). In a mature female this structure is usually lacking entirely.
In California, sexual development and maturity patterns differ from locality to locality, and from generation to generation within the same locality. The change of sex occurs generally in 2 waves; the first wave in the 2nd yr of life (age-group I), and the second wave in the 3rd yr of life (age-group II). In his sexing of shrimp from Morro Bay and Bodega Bay, Rubtzoff (in press) observed a third wave of individuals changing from male to female in their 4th yr of life (age-group III). He also noted that shrimp which become females in their 2nd yr of life do not mature as a functioning male, even though they develop some external male characters before they start to change to females.
There is a difference in growth rate between males and females in autumn and winter. In Norway, the growth rate of P. borealis females increases prior to spawning, at a time when that of the males is decreasing (Rasmussen, 1953). P. jordani shows the same growth pattern in autumn in California. In winter, females are ovigerous and do not grow at all; males grow slowly and increase their rate of growth in late winter or early spring, before the females do, and thus catch up with them.
Rasmussen (1953) found that the growth rate is dependent largely upon temperature. In a temperate environment, shrimp grow faster than in a cold environment. He found also that the pattern of sex change depends upon rate of growth. In California, analysis of growth data indicates that other factors besides growth rate may play a role in determining the proportion of shrimp changing sex at a given age. Rubtzoff (in press) observed that in the Bodega Bay area, the proportion of shrimp becoming females in their 2nd yr of life was much higher in the 1954 year-class than in the 1953 year-class. The average size of animals in their 2nd yr was less for the 1954 year-class than for the 1953 year-class. Subsequent sampling at Bodega Bay from 1958 to 1965 has revealed little or no correlation between sex change and growth rate (Dahlstrom, unpublished data).
In British Columbia, P. jordani matures as a male, and in a minority of specimens as a female, at about 18 mo; the average carapace length is then 17.6 mm and the weight 3.8 g. At 2 ½ yr all are in the female phase, averaging 20.2 mm in carapace length and 5.8 g in body weight (Butler, 1964).
Fig. 2 Endopodite of 1st pleopod of P. jordani at different stages of development: (a) 2 to 3 mo old immature shrimp. (b) About 3 mo old immature shrimp, showing first appearance of organ of copulation. (c) to (e) Development of organ of copulation, accompanying change of immature shrimp into male. (f1) 1 yr old male. (g1) to (i1) Degeneration of organ of copulation and simultaneous elongation of tip of endopodite, accompanying change from male to female in 2nd yr of life. (j1) 1 ½ yr old female. (f2) 2 yr old male. (g2) to (i2) Degeneration of organ of copulation and elongation of tip of endopodite, accompanying change from male to female in 3rd yr of life. (j2) 2 ½ yr old female. (f3) 3 yr old male. (g3) individual changing to female in 4th yr of life. (j3) 3 ½ yr old female. (k) 4 ½ to 5 ½ yr old female. Corresponding stages in animals of different age are designated by identical letters. (Rubtzoff, in press)
Fig. 3 Appendix masculina (projecting to left and attached at base of appendix interna of 2nd pleopod) in P. jordani at different stages of development. (c) to (e) Development of appendix masculina accompanying change of immature shrimp into male. (f1) 1 yr old male. (g1) to (i1) Degeneration of appendix masculina accompanying change from male to female in 2nd yr of life. (f2) 2 yr old male. (g2) to (i2) Degeneration of appendix masculina accompanying change from male to female in 3rd yr of life. Letters identical with those in Fig. 2 designate corresponding phases in transformation of appendix masculina and endopodite of 1st pleopod. (Rubtzoff, in press)
In samples collected at Morro Bay, California, in 1954, males at 18 mo averaged 17.7 mm in carapace length and 3.9 g in weight. At 2 ½ yr, mature males averaged 19.9 mm in carapace length and 5.7 g in weight, while mature females of the same age averaged 21.6 mm in carapace length and 6.8 g in weight.
Samples collected at Bodega Bay, California, in 1954, revealed that mature males at about 18 mo averaged 17.5 mm in carapace length and 3.7 g in weight. At 2 ½ yr, mature females averaged 20.7 mm in length and 6.0 g in weight.
No data, but probably promiscuous.
No data, but probably external.
The usual number of eggs carried by a female is between 1,000 and 3,000. Small individuals in their 2nd yr of life have been found carrying as few as 900 eggs, whereas larger individuals in their 3rd or 4th yr of life have been found with up to 3,900 eggs. The larger and older females generally carry more eggs, but the relationship between size and fecundity differs between different populations, as shown by the examples from the Fort Bragg shrimp beds (Fig. 4) and those of Eureka-Crescent City (Fig. 5).
One brood is produced each year. It is not known how many broods can be produced in a lifetime, but female mortality is high during or shortly after the ovigerous period, and so many females breed only once. Sampling of the catches in California during the ovigerous period reveals a marked decrease in the number of females from the previous autumn. The most noticeable decrease is in the number of females during the latter part of their 3rd yr and the initial part of their 4th yr of life. Allen (1959) reported a high mortality rate for P. borealis during the spawning period. He estimated that 50 percent of the 18 mo old prawns die. This mortality takes place at egg-laying rather than egg-hatching, and he also suggested that there is evidence of a second heavy mortality at 31 months.
Gonads begin developing during the summer, and in the autumn the maturing bluish-green ovaries are visible within the carapace. At the last molt preceding spawning, the pleopods of the female develop special ovigerous setae. After the eggs are fertilized, they are attached and are interconnected by a network of mucous threads.
The ovigerous period shows slight variation between different areas along the Pacific Coast. Butler (1964) reported that spawning in southern British Columbia begins in the last half of November and the ovigerous period continues until April, a period of about 4 ½ mo. Magill and Erho (1963) reported that spawning generally commences in the area of Grays Harbor, Washington, in early October and the ovigerous period continues until the first part of April. In northern Oregon, spawning begins somewhat earlier (about the 1st October) and the ovigerous period terminates generally before the 1st April. In northern California, observations indicate spawning starts about the middle of October, and the ovigerous period ends about the middle of May. The ovigerous period in the Morro Bay area, off the central California coast, starts about the end of October and extends to the first part of June (Rubtzoff, in press). The average ovigerous period is estimated to be about 5 months.
Peak spawning off British Columbia, Washington, and Oregon appears to be in December, when 100 percent of the females can be found ovigerous. In California, December and January seem to be the peak months of spawning.
Tegelberg and Smith (1957) reported that the larger females start spawning first and also release their larvae first. Females of only 20 mo may first become ovigerous in November.
The eggs are ellipsoid in shape and range from about 0.70 to 2.00 mm in length, depending upon the period of incubation. There appears to be no direct correlation between egg-size and the carapace-size of the parent. Freshly spawned eggs from Bodega Bay in November 1964 had an average length of 0.85 mm, with a range of 0.70 to 1.00 mm, and the width was between 0.55 to 0.59 mm. Rubtzoff (in press) found eggs to range from 1.00 to 2.00 mm in length, with the most common sizes ranging from 1.20 to 1.60 mm. It is believed that his samples were obtained from Morro Bay in February to April, after about 3 to 5 mo of incubation; this could account for the size difference. Mistakidis (1957) reported a size increase in P. montagui eggs from about 0.78 mm in November to between 1.00 to 1.20 mm by April and May.
The color of the eggs when first spawned is a bluish-green. With the gradual development of the egg, the color fades to a light green with a tint of gray.
Fig. 4 Relationship between size and fecundity of P. jordani from the Fort Bragg shrimp bed. November 1964. Line fitted by least squares method.
Fig. 5 Relationship between size and fecundity of P. jordani from the Eureka - Crescent City shrimp bed. November 1964. Line fitted by least squares method.
Rubtzoff (in press) recorded development of eggs from Morro Bay and Bodega Bay at various times during the ovigerous period. He noted that in February, which corresponds to the middle of the ovigerous period in California, only a large clump of yolk was visible in some of the eggs, whereas in others the eyes of the developing embryo could be seen as 2 long black dots (Fig. 6a, b). By April, the embryo could be clearly seen in most of the eggs. The compound eyes had increased in size and appeared to be oval in shape. The ocellus was a small black dot located between the compound eyes. Several orange chromatophores could be seen on the white body of the embryo (Fig. 6o to e). In early May, near the end of the ovigerous period, most eggs contained embryos in which the pereiopods were distinct. The compound eyes had become larger and rounder and there were more orange chromatophores (Fig. 6f to h). The stage of development of the embryo varied somewhat from egg to egg in each female; therefore, it is unlikely that all eggs of any female would hatch at the same time.
Modin and Cox (1967) reared P. jordani in the laboratory from the egg through complete metamorphosis. They determined that the larvae passed through 11 to 13 zoeal stages, but acknowledge that the artificial laboratory conditions may cause a greater number of larval stages than occur under natural conditions. Duration of the various larval stages ranged from 4 to 12 days, with an average of 6.8 days. Size or total length of the larvae, rather than age or the number of molts through which the larvae passed, could be correlated better with a given degree of development. One shrimp completed metamorphosis in 79 days, after passing through 11 zoeal stages. Two others were in the 12th and 13th zoeal stages and were 74 and 85 days old, respectively, when they died.
First stage larvae (Fig 7A) measured approximately 5 mm from the posterior margin of the telson to the anterior tip of the antennal scale. This stage can be identified by the rudimentary pereiopods, large immobile, unstalked eyes, and the absence of uropods. Approximately 34 days after hatching, many larvae had reached the 6th zoeal stage (Fig. 7F) and had completed about one-half of their larval development. This stage is about 9.5 mm long and has 8 or 9 dorsal rostral spines. The antennal flagellum has become segmented; the maxilla has increased in size and bears a correspondingly higher number of setae; the pereiopods have become functional; and the telson has become rectangular and setose (Fig. 7G to J).
In the laboratory the 11th stage was reached approximately 68 days after hatching, and this was usually the final larval stage before metamorphosis into the adolescent or postlarval phase. This larva is about 17 mm long and can be identified by the long antennal flagellum, heavy setose pleopods, and the appearance, for the first time, of inferior, rostral spines (Fig. 8A). It is not known what type of food constitutes the larval shrimp diet in nature, but nauplii of brine shrimp, Artemia salina, cultivated in the laboratory, proved to be a suitable diet throughout the experiment.
Not much is known about juvenile shrimp, except they have been caught incidentally with adult shrimp off Crescent City, California, as early as June when about 2 mo old. At this time, they average about 4.5 mm in carapace length. Growth is rapid, and when 5 mo old, in September, they average about 8.0 mm. From October to March, they increase about 6.5 mm in carapace length, and reach an average size of about 14.5 mm. At this time, they are 1 yr old, and most will reach maturity either as males or females during the summer and autumn (Rubtzoff, in press).
The life expectancy of the species is 2 to 4 yr. Most shrimp taken in the commercial catch are 2 to 3 yr old. The maximum age appears to be 4 yr, but it is difficult to age the shrimp after 3 yr of age. During some years in California, the bulk of the commercial catch consists of group I shrimp (shrimp in the 2nd yr of life). Rate of growth appears to be faster in California than in the other Pacific Coast states and Canada, and sexual maturity occurs earlier in more of the females. Therefore, because many females die after spawning, the average and maximum longevity is lower in California.
In aquaria, ocean shrimp can survive for several months, provided that the water is cool and bacteria free, and the shrimp are fed regularly. Modin and Cox (1967) were able to keep female shrimp alive for approximately 5 mo by feeding them adult brine shrimp. On this food alone these ocean shrimp were carried through the ovigerous period and several molted. Water temperature were maintained between 10 and 13°C, and the water was changed every 10 days. Fifty shrimp were placed in the aquaria initially, and after 5 mo there were 12 survivors.
Fig. 6 Eggs of P. jordani at various stages of development. (a) (b) Morro Bay, 21 February 1955, about 2 mo after fertilization. (c) to (e) Morro Bay, 8 April 1955, about 4 mo after fertilization: (c) dorsal; (d) ventral; (e) lateral (f) to (h) Bogeda Bay, 3 May 1955, about 5 mo after fertilization: (f) dorsal; (g) ventral; (h) lateral. Yolk stippled; ocellus is visible between compound eyes in (c) and (f); chromatophores are present in (c) to (h). (Rubtzoff, in press)
Fig. 7 Larval development of P. jordani. (A) to (E) 1st stage; (A) lateral view; (B) antenna; (C) maxilla; (D) 2nd pereiopod; (E) telson. (F) to (J) 6th stage: (F) lateral view; (G) antenna; (H) maxilla; (I) 2nd pereiopod; (J) telson. (Modin and Cox, 1967)
When this species is taken from deep water, many seem to have difficulty regaining balance, and they flounder about aimlessly; nevertheless, most recover if placed in suitable water.
Fish, such as Pacific hake (Merluccius productus), sablefish (Anoplopoma fimbria), arrowtooth flounder (Atheresthes stomias), spiny dogfish (Squalis acanthias), skates (Raja spp.), rex sole (Glyptocephalus zachirus), slender sole (Lyopsetta exilis), and invertebrates such as starfish and urchins are the principal competitors.
The fish competitors, except rex and slender soles, are also the principal predators. Very few competitors are taken in catches from areas of good shrimp density, and schooling may be a defense reaction. P. jordani is armed with a long rostrum and is able to back up and dart away with great speed. This may discourage some predators.
Very little is known of the natural feeding habits of P. jordani. However, observations of feeding in captivity indicate that the food is generally captured with the 2nd pair of pereiopods and brought to the mouth parts. Food may be captured while the shrimp is on the bottom or swimming.
Stomach analysis of shrimp caught off the northern California coast indicates the shrimp are primarily detritus feeders. Stomach contents included much mud and the remains of Polychaeta, Porifera, diatoms, and appendages of amphipods and isopods (Gotshall, personal communication).
Growth rates vary according to region, and also by sex and year class. Growth rates of shrimp sampled off Vancouver Island, British Columbia, from 1960 to 1962 (Butler, 1964) are similar to those of shrimp off Fort Bragg and Bodega Bay, California, during approximately the same period (Fig. 9). At 1 ½ yr, the mean carapace lengths were 17.6, 18.0, and 18.4 mm for the 3 respective areas. At 2 yr, the means were 17.9, 18.7, and 19.2 mm; and at 3 yr the means were 20.9, 21.8, and 22.2 mm, respectively. The growth rate of the species off Washington and Oregon appears to be somewhat slower than off British Columbia and California. According to Magill and Erho (1963), the modes of the 1954-, 1957-, and 1958-year classes, off the coast of Grays Harbor, Washington, at 2 yr of age were 15.0, 17.1, and 16.2 mm carapace length, respectively. At 3 yr, the 1954 year-class peaked at 18.5 mm and the 1957 year-class at 20.0 mm. Growth rates for shrimp off the northern Oregon coast were faster than those off Grays Harbor, Washington. Modes for the 1957, 1958, and 1959 year-classes at 2 yr of age were 17.4, 17.0, and 16.0 mm. At 3 yr of age, the 1957 year-class peaked at 21.6 mm and 1958 year-class at 20.0 mm.
In spite of the variations in growth rate which have been mentioned, there is a clear pattern of seasonal growth. During the first summer, growth is rapid; it slows down slightly during winter, but resumes at a rapid pace in the second spring and summer until about August, when growth of males retards. Growth during this period (from the first to the second summer) averages almost 1 mm carapace length increase per month. The growth of the transitionals proceeds at the same rapid rate during the second autumn until about the end of October. At this time most transitionals have become females, and, when the sex change is completed, growth virtually ceases. Some shrimp remain male until the following year; such specimens grow more slowly than the transitionals and females during the second summer and autumn.
Differential growth between the sexes results in a bimodal size curve for the same year class. Growth patterns of P. jordani off the coast of Fort Bragg, California, during 1960 and 1961, are shown in Fig. 10 and 11. Both males and females grow slowly during the winter months (the females actually stop growing during the ovigerous period). In the spring, when the shrimp are approximately 2 yr old, growth in males accelerates earlier than in females, and many of the larger males begin to change sex. Females, which had changed sex the previous year, resume growth in the early summer, after the ovigerous period. By November, at the age of about 2 ½ yr, practically all members of the year class are females and are entering the ovigerous period. Determining growth rates and age of females after this time is very difficult because of the reduced growth rate and apparent high natural mortality.
Migrations of P. jordani appear to be mostly local and no movement of great distance is involved.
At Morro Bay, California, during the winter spawning migration, females move 3 to 5 km offshore from a depth of about 183 to 256 m. Shorter spawning migrations take place in the other California areas with a depth increase of 18 to 37 m.
Fig. 8 Eleventh stage larva of P. jordani.
(A) lateral view; (B) antenna; (C) maxilla; (D) 2nd pereiopod;
(E) telson. (Modin and Cox, 1967)
Fig. 9 Comparison of growth rates of Pandalus jordani from Bodega Bay and Fort Bragg, California, (original data), and from Vancouver Island, British Columbia, (data from Butler, 1964). Specimens hatched in spring of 1960; October dates correspond to ages of approximately 6, 18 and 30 mo. All sexes combined.
Fig. 10 Percentage size-composition of P. jordani from off the coast of Fort Bragg California, 1960–1961. N = number of specimens.
Fig. 11 Percentage size-composition of P. jordani off the coast of Fort Bragg, California, 1961. N = number of specimens.
Summer migration can be either inshore or offshore and in either direction coastwise. This type of movement appears to be associated with the search for food. The inshore-offshore movements are generally over short distances within a depth range of 37 m, but the coastwise migrations probably frequently cover 8 to 16 km, and sometimes more. These movements do not appear, however, to be the result of one long migration. Environmental disturbances by strong winds and tides also may cause the shrimp to move.
Evidence of diurnal vertical movements of P. jordani was noted by comparative night and day trawling; this resulted in excellent catches during the day and poor catches at night (Schaefers and Johnson, 1957). Movement off the bottom at night also was demonstrated by midwater trawl catches off Vancouver Island, British Columbia, by the research vessel JOHN N. COBB. A tow with a midwater trawl at depths of 80 to 91 m over bottom depths of 199 to 221 m caught 186 individuals (Anon., 1956).
The ocean shrimp is a schooling species, and most of the time all sizes, sexes, and ages can be found within the school. At other times, notably in winter and spring, younger individuals occur toward the inshore side of the school and the larger and older on the offshore side, in deeper water. In general, the size and shape of the school are irregular and depend upon the density and strength of the year classes making up the population. Usually, there is only one school on a shrimp bed. Where density of the school is high, almost pure catches can be made with few incidental fish and invertebrates being taken. The distribution pattern of the school is constantly changing in size and shape because of movements influenced by the environment, disturbances caused by fishing, and losses due to fishing and natural mortality (Dahlstrom, unpublished data).
Sex ratio depends upon the age structure and year-class strength of the population. Because P. jordani undergoes sex change during the summer, sex ratio is affected by the time of year. Off Washington and Oregon, the percentage of males to females varies throughout the year from about 70% female and 30% male in the spring to about 60% male and 40% female in the autumn (Magill and Erho, 1963). This ratio is reversed off California with higher percentages of males occurring in the spring and higher percentages of females in the autumn. The greater number of primary females in California waters probably accounts for this difference. At Bodega Bay, California, in July 1965, when group I shrimp (individuals in their 2nd yr of life) made up 87% of the population, the sex ratio was 20% males, 56% transitionals, and 24% females. No samples were taken in October, but the sex ratio was probably about 20% male and 80% female. On the spawning grounds females probably account for 80 to 100% of the population (Dahlstrom, unpublished data).
Age composition depends on the strength of the incoming year-class and the survival of the older year classes. In California, the fishery is largely composed of group I and II shrimp (individuals in their 2nd and 3rd yr of life), whereas in Oregon and Washington, larger numbers of group III shrimp (individuals in their 4th yr of life) are taken.
Occasionally, individuals from age group O are taken in the autumn, but the small shrimp of this group are generally not available to the commercial gear and escape through the meshes. A better idea of the relative abundance of this group has been obtained by using small mesh nets during research cruises. These juveniles occupy much of the same area as the adults.
The length composition of the populations generally ranges from about 4 to 26 mm carapace length. Occasionally, exceptionally large individuals (30 mm carapace length) have been taken in Morro Bay, California. Butler (1964) reported measuring a 29.3 mm (carapace length) female in British Columbia.
TABLE I
Carapace length ranges (in mm) by age group for P. jordani off the coast of Crescent City, California, May to September 1959
| Month | A g e G r o u p | ||
| I | II | III | |
| May | 12.4 – 18.2 | 18.4 – 21.2 | 21.4 –24.4 |
| June | 13.0 – 18.4 | 18.6 – 21.6 | 21.8 – 23.6 |
| July | 14.2 – 18.4 | 18.6 – 21.6 | 21.8 – 24.0 |
| Sept. | 15.2 – 18.8 | 19.0 – 21.6 | 21.8 – 24.0 |
Length composition of the catch for each group varies according to region and season. Shrimp in their 2nd yr of life enter the catches earlier in the season in California than do similar shrimp off the northern Oregon and Washington coasts, and because of the faster growth rate, become available to the net sooner. Size ranges of age groups from sampling the catches off Crescent City, California, in 1959 are shown in Table I. Off northern Oregon and Washington, the incoming year-class enters the fishery from February to April at about 12 mo of age, and a carapace length of 10 to 12 mm. Shrimp appear to reach a greater age off northern Oregon and Washington than off California, and more shrimp are represented in group III. Northern Oregon and Washington shrimp eventually reach the same size range as females in California, but most of the transition from male to female occurs in their 3rd yr of life (group II shrimp).
Larger (older) shrimp frequently occur in the deeper water occupied by the school.
Size (carapace length) at first capture by the commercial gear is around 10 to 12 mm, although individuals of about 8 mm have been taken incidentally with the adults in August or September. These small shrimp are unmarketable.
Size at maturity ranges from about 15 to 18 mm carapace length for males and from about 17 to 20 mm for females.
The length-weight relationships of P. jordani off the coast of Eureka and Crescent City, California, in 1961 were determined by Jow (personal communication) and are illustrated in Fig. 12. Formulas for monthly length-weight relationships were determined by the method of least squares, using the exponential equation: W = CLn, where W = weight, L = carapace length, and C and n were derived empirically. Formulas for monthly periods were as follows:
| July | Log W = -2.97806 + 2.79415 Log L |
| August | Log W = -2.89604 + 2.74741 Log L |
| September | Log W = -3.11412 + 2.93255 Log L |
| October | Log W = -3.07019 + 2.91237 Log L |
Fig. 12 Length-weight relationship for P. jordani off the coast of Eureka and Crescent City, California, from July to October, 1961. (Jow)
Population estimates have been made of the various shrimp schools in California. Off Crescent City and Eureka, the population each year has averaged about 2.0 million kg of shrimp in April. Generally, the heads-on count per kg of shrimp at this time averages about 286. Therefore, the number of shrimp would be approximately 600 million.
Abundance changes are rapid during the summer, and the effects of fishing, predation, and other factors result in a steady mortality. Off Eureka and Crescent City, the post-season shrimp population estimate in 1966 (August and September) revealed about 26 percent of the April population remaining (Dahlstrom, Gotshall and Willis, 1967).
The density of the population within a shrimp school appears to remain about the same. Judging by the pattern of fishing locations, the most noticeable differences are the changes in size and shape of the schools. Based upon an average catch of 227 kg/h and heads-on count of 220 per kg, approximately 50,000 shrimp would be taken in an hour. If the tow is made at 4 km/h with a net opening of 10.7 m, the bottom area covered would be about 48,931 m2 (10.7 m × 4,573 m). This would be equivalent to about 1 shrimp per 0.9 m2. While the distribution pattern is not known, the spacing between shrimp is suspected to be closer than this because of certain void areas within the school. Catches as high as 1,360 kg/h have been made. At this rate, the average density for the same area would be about 6 shrimp per 0.9 m2.
Observations of the catches per unit of fishing effort (catch/h) generally indicate that highest catch rates occur during the first few months of the season. At Bodega Bay, California, during 1965, the average catch was 361, 376, and 181 kg in May, June and July, respectively. Observation of fishing logs indicate declining catch rates during prolonged fishing by a fleet over a small area. This activity may disturb and scatter the school of shrimp.
Spawning population estimates of the Eureka-Crescent City shrimp population for the years 1960 to 1963 reveal the number of females to range from 45 million to 104 million. These estimates were obtained from post-season cruise data. At an average of about 2,000 eggs per female (Fig. 5), the total number of eggs produced each year ranged from about 9 × 1010 to 21 × 1010.
The mean annual recruitment to the fishable stock in the Eureka-Crescent City, California, fishery is estimated to be about 400 million shrimp. Recruitment occurs in May when the fishery begins, and most group I (13 mo) shrimp are catchable. The total weight would be approximately 750,000 kg, estimating 528 individuals per kg. Recruitment can show large variations from year to year. In this same area, it was estimated to be 960 million shrimp in 1965 (1964 year class) and 350 million shrimp in 1966 from the 1965 year class (Gotshall and Dahlstrom, 1966; Dahlstrom, Gotshall and Willis, 1967).
Analysis of the data indicates no correlation between recruitment and spawning stock. Further analysis of the relationship between recruitment and the rate of reproduction is needed because of the variation in abundance of spawning females of different year-classes from season to season. Group I females carry considerably fewer eggs than group II or group III females, and survival rates of larvae produced by different year-class females may vary.
Mortality rates appear to vary from year-class to year-class, as well as from season to season. Estimates for total mortality rates of the shrimp population off Eureka and Crescent City, California, for 1-yr periods from April 1960 to April 1966 ranged from 48 to 70 percent, with a mean of 61 percent. Instantaneous mortality rates (i) were determined (Gotshall, unpublished data) during periods of fishing and no fishing for the same area from June 1965 to September 1966 (Table II). The instantaneous mortality rate is equal to the natural logarithm (with sign changed) of the complement of the annual (actual) mortality rate.
The effects of physical factors, such as salinity and temperature, upon shrimp mortality is not known. Predators appear to be a major factor in natural mortality. In years of good shrimp recruitment, many fish species, such as hake, sablefish, arrowtooth flounder, spiny dogfish, and skates, can be found feeding heavily on young shrimp.
Fishing is a major factor in total mortality. In California, where there is a season and quota, fishing generally is conducted during the spring and summer months until the area quota is reached or the season ends (31 October). This limits fishing mortality; however, Washington and Oregon do not have quotas and a greater fishing mortality is possible.
The community consists of many species of flatfish, rockfish, skates, sharks, miscellaneous fishes, and invertebrates. The most common fish are slender sole (Lyopsetta exilis), rex sole (Glyptocephalus zachirus), Dover sole (Microstomus pacificus), Pacific sanddab (Citharichthys sordidas) and Pacific hake (Merluccius productus). Morgan and Gates (1958) determined the species composition and weight of incidental fish catches contained in shrimp tows off California and Oregon in 1958 (see Table III).
TABLE II
Mortality rates for shrimp off Eureka and Crescent City, California (Gotshall, unpublished data)
| Time Period | Instantaneous Mortality Rate (i) | Type of Mortality | |
| 1963 Year Class | 1964 Year Class | ||
| June 1965 to Oct. 1965 | .506 | 1.752 | Fishing and natural |
| June 1965 to April 1966 | 1.396 | 1.139 | Fishing and natural |
| Oct. 1965 to April 1966 | 2.164 | .730 | Natural |
| Oct. 1965 to Sept. 1966 | 3.575 | 1.481 | Fishing and natural |
| April 1966 to Sept. 1966 | 5.691 | 2.607 | Fishing and natural |
TABLE III
Numbers and weights of fish and invertebrate species caught by different types of gears (Morgan and Gates, 1958)
| S P E C I E S | G E A R | ||||||
| Balloon Trawl | Flat Trawl | Beam Trawl | |||||
| Number | Weight (pounds)1 | Number | Weight (pounds)1 | Number | Weight (pounds)1 | ||
| FLATFISH | |||||||
| Dover sole | Microstomus pacificus | 2,189 | 2,694 | 1,085 | 1,298 | 466 | 521 |
| Rex sole | Glyptocephalus zachirus | 4,604 | 722 | 2,375 | 373 | 1,029 | 148 |
| Slender sole | Lyopsetta exilis | 10,112 | 721 | 4,897 | 368 | 2,041 | 179 |
| Pacific sanddab | Citharichthys sordidus | 1,458 | 110 | 657 | 34 | 964 | 114 |
| Arrowtooth flounder | Atheresthes stomias | 350 | 475 | 176 | 186 | 27 | 28 |
| English sole | Parophrys vetulus | 79 | 84 | 16 | 24 | 15 | 14 |
| Petrale sole | Eopsetta jordani | 23 | 36 | 15 | 36 | 4 | 8 |
| Curlfin turbot | Pleuronichthys decurrens | 2 | 3 | 2 | |||
| TOTAL | 18,817 | 4,842 | 9,221 | 2,319 | 4,549 | 1,014 | |
| ROCKFISH | |||||||
| Canary rockfish | Sebastodes pinniger | 47 | 170 | 4 | 16 | 1 | 5 |
| Bocaccio | S. paucispinis | 26 | 108 | 3 | 15 | -- | -- |
| Chilipepper | S. goodei | 31 | 75 | 12 | 49 | -- | -- |
| Yellowtail rockfish | S. flavidus | 3 | 14 | -- | -- | 2 | 5 |
| Flag rockfish | S. rubrivinctus | 17 | 22 | 5 | 11 | 1 | 5 |
| Black rockfish | S. melanops | 1 | 22 | -- | -- | -- | -- |
| Greenspotted rockfish | S. chlorostictus | 9 | 10 | 1 | 2 | -- | -- |
| Pacific ocean perch | S. alutus | 138 | 105 | 28 | 18 | 19 | 11 |
| Blackmouth rockfish | S. crameri | 201 | 86 | 83 | 29 | 32 | 14 |
| Splitnose rockfish | S. diploproa | 111 | 32 | 148 | 43 | 40 | 5 |
| Greenstriped rockfish | S. elongatus | 198 | 139 | 39 | 10 | 28 | 9 |
| Stripetail rockfish | S. saxicola | 572 | 269 | 303 | 132 | 65 | 23 |
| Shortbelly rockfish | S. jordani | -- | -- | -- | -- | 1 | 1 |
| Unidentified rockfish | Sebastodes sp. | 85 | 114 | 21 | 2 | 9 | -- |
| Shortspine channel rockfish | Sebastolobus alascanus | 248 | 126 | 165 | 76 | 22 | 7 |
| TOTAL | 1,687 | 1,292 | 812 | 403 | 220 | 85 | |
| SKATES AND SHARKS | |||||||
| Longnose skate | Raja rhina | 659 | 622 | 127 | 279 | 35 | 104 |
| Big skate | R. binoculata | 22 | 305 | 3 | 22 | 7 | 151 |
| California skate | R. inornata | 79 | 207 | 45 | 67 | 9 | 17 |
| Unidentified skates | Raja sp. | 29 | 68 | 30 | 169 | -- | -- |
| Pacific electric ray | Torpedo californica | -- | -- | -- | -- | 2 | 8 |
| Ratfish | Hydrolagus colliei | 69 | 91 | 21 | 37 | 3 | 6 |
| Spiny dogfish | Squalus acanthias | 50 | 120 | 15 | 6 | 1 | 3 |
| Pacific hagfish | Polistotrema stouti | 3 | 1 | 12 | 1 | 46 | 6 |
| TOTAL | 911 | 1,414 | 253 | 621 | 103 | 295 | |
| MISCELLANEOUS | |||||||
| Lingcod | Ophiodon elongatus | 22 | 129 | 7 | 106 | 3 | 16 |
| Sablefish | Anoplopoma fimbria | 355 | 796 | 98 | 176 | 48 | 79 |
| Pacific hake | Merluccius productus | 1,807 | 2,854 | 167 | 277 | 358 | 657 |
| Cottids | Cottidae | 511 | 26 | 545 | 23 | 96 | 4 |
| Sea poachers | Agonidae | 575 | 19 | 2,282 | 92 | 398 | 27 |
| Eel pouts | Zoarcidae | 781 | 38 | 592 | 31 | 434 | 17 |
| Miscellaneous species | 38 | 7 | 2 | 1 | 16 | 4 | |
| TOTAL | 4,089 | 3,869 | 3,693 | 706 | 1,353 | 804 | |
| TOTAL FISH | 25,504 | 11,417 | 13,979 | 4,049 | 6,225 | 2,198 | |
| Crabs | 81 | 145 | 59 | 68 | 22 | 30 | |
| Invertebrates | -- | 2,269 | -- | 2,529 | -- | 252 | |
| TOTAL INVERTEBRATES | 81 | 2,414 | 59 | 2,597 | 22 | 282 | |
| Shrimp | Pandalus jordani | -- | 1,985 | -- | 1,523 | -- | 1,040 |
The present commercial gear consists mostly of Gulf of Mexico semiballoon shrimp trawls with 18 m headropes. Mesh size ranges from 32 to 44 mm stretch measure between knots, depending upon minimum mesh size regulations set by individual states. The nets are usually made of nylon. The nylon twine ranges in size from about No. 18 thread in the body to about No. 42 thread in the cod end.
Prior to 1958, only beam trawls were legal in Oregon and California (Fig. 13). Starting in 1963, any trawl became legal in California, providing the mesh size was 38 mm stretch measure between the knots.
Shrimp are caught mainly by combination boats, which are also capable of fishing for crab, salmon, albacore, and bottomfish. These boats are 15 to 24 m in length. Conversion to shrimp fishing is relatively simple for most of these vessels; therefore, they may enter the fishery during slack periods or closed seasons of the other fisheries. The number of boats entering the fishery depends upon the abundance, availability, and demand of shrimp. This number could range from 20 to 30, depending upon the above factors. Most vessels are equipped with loran, depth sounder, and radio equipment, and several are equipped with radar (Magill and Erho, 1963).
Since 1952, this species has supported fisheries from Morro Bay, California, (INE, 232) to near Destruction Island, Washington, (INE, 231) (Fig. 14 and 15).
Fishable concentrations are located on the continental shelf from 5 to about 24 km offshore, at depths usually between 91 and 182 m.
The areas of greatest abundance are off Crescent City, California; Coos Bay and Tillamook Head, Oregon; and Grays Harbor, Washington.
Shrimp have been fished as shallow as 73 m off Bodega Bay, California, and as deep as 237 m off Morro Bay, California.
Fishing generally occurs in the summer off the states of Washington, Oregon, and California, but is controlled by weather, economic factors and season regulations.
California's season begins 1 May and ends 31 October. The season in Oregon opens 1 March and closes 31 October. Washington does not have a closed season, but fishing is usually conducted from March to October. Peak catches are usually in June and July.
The season may close earlier in any of the four fishing areas in California if the poundage quota for an area is reached. California's season corresponds closely to the period when female shrimp are not carrying developing eggs. There is no poundage quota in Oregon, except that, when California's northernmost bed in Area A (Fig. 14) is closed because of quota attainment, deliveries into Oregon of shrimp caught off California are prohibited by Oregon regulations.
The unit of effort used is one hour of fishing, regardless of the type or size of trawl or the trawling speed. Records of landings and hours fished have been compiled for all fishing areas in Washington, Oregon, and California. In general, the average catch per hour in California has been about 226 kg/h since the start of the fisheries (Table IV). Daily catch rates up to 1,360 kg/h have been made, but the highest rate for a season was 433 kg/h recorded at Fort Bragg, in 1961. Catch rates of about 136 kg/h seem to be the minimum to sustain a fishery.
Total fishing intensity varies from year to year, depending upon abundance, availability, and demand of shrimp (Tables V to VIII). Within a season and area, fishing effort and catch rate vary by month (Table IX).
In California prior to 1957, 28 mm was the legal minimum mesh size for shrimp nets. Since that year, meshes may not be less than 38 mm stretch measure inside the knots. Net mesh tests show that the larger mesh size allows for greater escapement of group I shrimp, which then have a chance to mature as either males or females.
Fig. 13 Shrimp boat with beam trawl entering port at Fort Bragg, California, 1961.
(W.A. Dahlstrom)
Fig. 14 P. jordani fishing areas and location of shrimp beds in California (Dahlstrom).
Fig. 15 Principal P. jordani fishing areas along the Washington, Oregon and northern California coasts (Magill and Erho, 1963).
TABLE IV
Landings, effort and catch per unit of effort for P. jordani in California, 1952–66
| Year | Landings (kg) | Effort (h) | Catch/h |
| 1952 | 93,445 | 332 | 281 |
| 1953 | 133,834 | 710 | 188 |
| 1954 | 135,973 | 699 | 194 |
| 1955 | 388,224 | 1,569 | 247 |
| 1956 | 530,742 | 2,134 | 248 |
| 1957 | 646,661 | 2,540 | 254 |
| 1958 | 784,823 | 3,988 | 196 |
| 1959 | 809,774 | 3,075 | 263 |
| 1960 | 919,344 | 3,798 | 242 |
| 1961 | 910,039 | 2,761 | 329 |
| 1962 | 810,255 | 3,564 | 227 |
| 1963 | 950,411 | 4,165 | 228 |
| 1964 | 444,800 | 1,984 | 224 |
| 1965 | 646,772 | 3,155 | 205 |
| 1966 | 550,648 | 2,749 | 200 |
TABLE V
Pandalus jordani Landings and Effort Area A, Crescent City - Eureka, California
| Year | Quota (thousands of kilograms) | Landings (kg) | Effort (h) | Catch/h | No. of Boats |
| 1952 | 680 | 1,999 | 30 | 66 | 2 |
| 1953 | 680 | 20,532 | 221 | 92 | 4 |
| 1954 | 680 | 80,085 | 346 | 231 | 1 |
| 1955 | 680 | 227,262 | 1,040 | 218 | 3 |
| 1956 | 453 | 406,593 | 1,587 | 256 | 6 |
| 1957 | 453 | 340,561 | 1,485 | 229 | 6 |
| 1958 | 453 | 516,876 | 2,273 | 227 | 7 |
| 1959 | 566 | 597,828 | 2,066 | 289 | 11 |
| 1960 | 566 | 602,562 | 2,489 | 242 | 12 |
| 1961 | None | 547,422 | 1,924 | 284 | 9 |
| 1962 | 680 | 698,866 | 3,123 | 223 | 12 |
| 1963 | 907 | 844,752 | 3,813 | 221 | 15 |
| 1964 | 453 | 428,204* | 1,800 | 237 | 7 |
| 1965 | 453 | 529,774 | 2,706 | 195 | 15 |
| 1966 | 566 | 548,481** | 2,684 | 204 | 12 |
* Oregon landings from Area A included in Quota - 75,659 additional kilograms in 1964.
** Oregon landings from Area A included in Quota - 16,783 additional kilograms in 1966.
TABLE VI
Pandalus jordani Landings and Effort Area B-1, Fort Bragg, California
| Year | Quota (thousands of kilograms) | Landings (kg) | Effort (h) | Catch/h | No. of Boats |
| 1957 | 90 | 104,017 | 407 | 255 | 2 |
| 1958 | 90 | 149,557 | 750 | 199 | 5 |
| 1959 | 181 | 201,849 | 875 | 230 | 6 |
| 1960 | 204 | 240,751 | 830 | 290 | 7 |
| 1961 | 385 | 362,617 | 837 | 433 | 3 |
| 1962 | 113 | 113 | 1 | 113 | 1 |
| 1963 | 113 | 12,596 | 92 | 136 | 1 |
| 1964 | 113 | 322 | 11 | 29 | 2 |
| 1965 | 113 | 1,905 | 20 | 95 | 3 |
| 1966 | 113 | 1,719 | 25 | 68 | 2 |
TABLE VII
Pandalus jordani Landings and Effort Area B-2, Bodega Bay, California
| Year | Quota (thousands of kilograms) | Landings (kg) | Effort (h) | Catch/h | No. of Boats |
| 1952 | 340 | 1,545 | 17 | 90 | 2 |
| 1953 | 340 | 23,195 | 116 | 199 | 4 |
| 1954 | 340 | 51,362 | 216 | 237 | 2 |
| 1955 | 181 | 156,306 | 492 | 317 | 6 |
| 1956 | 181 | 124,148 | 547 | 226 | 2 |
| 1957 | 272 | 202,082 | 648 | 311 | 4 |
| 1958 | 181 | 78,445 | 577 | 135 | 7 |
| 1959 | 113 | None | 26 | Trace | 6 |
| 1960 | 113 | 35,244 | 260 | 135 | 5 |
| 1961 | 113 | None | 11 | -- | 4 |
| 1962 | 113 | 111,275 | 371 | 299 | 7 |
| 1963 | 113 | 92,976 | 259 | 358 | 4 |
| 1964 | 113 | 16,274 | 173 | 94 | 4 |
| 1965 | 113 | 114,987 | 418 | 275 | 4 |
| 1966 | 113 | 235 | 23 | 10 | 3 |
TABLE VIII
Pandalus jordani Landings and Effort Area C, Morro Bay, California
| Year | Quota (thousands of kilograms) | Landings (kg) | Effort (h) | Catch/h | No. of Boats |
| 1952 | 90 | 89,943 | 285 | 315 | 2 |
| 1953 | 90 | 90,320 | 373 | 242 | 2 |
| 1954 | 90 | 4,525 | 92 | 49 | 2 |
| 1955 | 90 | 655 | 37 | 17 | 2 |
| 1956 | Closed | Closed | -- | -- | - |
| 1957 | 68 | No Effort | -- | -- | - |
| 1958 | 68 | 39,944 | 347 | 115 | 2 |
| 1959 | 68 | 6,760 | 108 | 62 | 2 |
| 1960 | 113 | 33,989 | 219 | 155 | 3 |
| 1961 | 113 | None | None | -- | - |
| 1962 | 113 | None | None | -- | - |
| 1963 | 113 | 180 | Trace | Trace | 3 |
| 1964 | 113 | None | None | -- | - |
| 1965 | 113 | 105 | 11 | 9 | 1 |
| 1966 | 113 | 210 | 17 | 12 | 1 |
TABLE IX
Bodega Bay, California, (Area B-2) monthly shrimp landings, effort, catch-per-hour, number of vessels, and number of trips, 1965
| Month | Landings (kg) | Effort (h) | kg/h | No. of vessels | Trips |
| May | 35,468 | 98 | 361 | 4 | 26 |
| June | 62,600 | 226 | 276 | 4 | 41 |
| July* | 16,918 | 98 | 181 | 4 | 17 |
| Season Total 114,986 | 417 | 275 | 4 | 84 | |
* Quota reached and area closed on July 20
The total annual yield for the states of Washington, Oregon, and California, from 1957 to 1966 has ranged from 4.4 million kg (1958) to 1.4 million kg (1965), with the average almost 2.7 million kg (Fig. 16). The 1966 figures are preliminary, but it appears that about 2.7 million kg were landed. P. jordani is also taken off British Columbia and Alaska, but the amount cannot be ascertained because this species usually occurs in a mixture of other pandalids.
Total annual yield has varied considerably in Washington and Oregon, but the variations have been less in California (Fig. 17). Washington landings peaked at about 2.9 million kg in 1958, and then declined until 1966 when a slight increase was observed. Oregon landings, with the exception of 0.5 and 0.6 million kg in 1960 and 1961 respectively, increased since 1957 to a peak of 2.4 million kg in 1964. They decreased to about 0.8 million kg in 1965, and increased again to over 1.8 million kg in 1966. California's annual landings have varied between 0.4 million to 0.9 million kg.
It is not known what the maximum equilibrium yield is for each shrimp bed, but analysis of catch data, mortality rates, and population estimates suggests that the northern California bed off Crescent City and Eureka can sustain an annual harvest of 0.45 to 0.68 million kg.
Fig. 16 Annual landings of P. jordani by state (1956 through 1966).
Fig. 17 Annual landings of P. jordani for Washington, Oregon, and California combined (1957 through 1966).
California is the only state that sets annual quotas in each of its shrimping areas. The four regulatory areas, delineated in Fig. 14, are:
| Area A | Oregon-California border to False Cape; |
| Area B-1 | False Cape to Point Arena; |
| Area B-2 | Point Arena to Pigeon Point; |
| Area C | Pigeon Point to the Mexican border. |
Quotas for the 1966 season were 0.56 million kg in Area A, and 0.11 million kg each in Areas B-1, B-2 and C.
There are no limitations on the number of vessels or fishermen in any of the three states. In California, however, the master of each vessel must first secure a permit before engaging in shrimp fishing.
California has a closed season from 1 November to 30 April, but an area can be closed earlier if the quota is attained. Shrimp fishing in Oregon was permitted the year round until 1964, when an annual closure became effective from 1 November to 1 March. If California's Area A is closed prior to 31 October, Oregon authorities restrict Oregon landings of shrimp taken off the coast of California. Washington has no closed season and neither has British Columbia, except that in Burrard Inlet there is a closure from 1 December to 31 March, and no shrimp fishing is permitted in Vancouver Harbor and English Bay.
A summary of the history of the various regulations for each state is described as follows:
California:
In 1951, the California State Legislature enacted laws empowering the Fish and Game Commission to regulate the shrimp fishery. A 6 mo season was established initially from 1 April to 30 September or until the poundage quota for the area was attained. In 1954, the dates were changed from 1 May to 15 October. In 1961, the season was changed from 1 June to 31 October, and in 1963, the season was changed from 1 May to 31 October. No trawling is permitted within 5 km of shore, and landings of incidental fish were not allowed until 1965 when 227 kg of incidentally caught fish were permitted with each shrimp landing. In 1956, the Morro Bay fishery was closed due to low shrimp abundance. This area was re-opened by Commission action in 1957 when biologists found an increased population. Initial regulations in 1951 restricted fishing to beam trawls, with maximum width of 6 m and circumference of the net-mouth not exceeding 13.7 m. The net-mouth specification was deleted in 1960, and the beam trawl became restricted to a 1.8 m height. In 1961, a further change removed the height restriction and in 1963 the use of otter trawls was authorized. Limiting the gear to beam trawls was an attempt to keep the catch of fin fish by the small-mesh nets to a minimum. Beam trawls are less efficient than otter trawls for capturing fin fish. The bottomfish resource supports the established otter trawl fishery, which operates in the same general area as the shrimp fishery, and is limited to a net mesh size of not less than 114 mm.
The quota assigned to each area was determined initially by the area-density method. The area of concentration and the average catch/h were determined. From these data an estimate of the total population was made. The quota was set at approximately one-fourth of the total population to assure an adequate spawning stock. At the present time, catch and catch/h figures, shrimp school size, year class composition, spawning stock size, and other data are analyzed annually to determine the condition of the shrimp resource within each area and to assign its quota.
Oregon:
Beam trawls were the only legal gear prior to 1958. Lowering the landing fee to 0.2 cents per kg, and permitting the use of shrimp trawls with meshes of 31 to 51 mm (taut measure, knot to knot) gave the fishermen more incentive to fish for shrimp. In 1959, the Oregon Fish Commission adopted the limit of 1,360 kg of incidental fish to be landed per shrimp trip (Magill and Erho, 1963).
Washington:
In 1956, the winter closure on shrimp fishing was lifted to allow the new fishery to develop. Any type of trawl is allowed, providing the mesh size is between 38 and 51 mm. The regulations also require that the maximum distance between the doors and the wings of the net is not to exceed one-half the length of the vessel. This regulation eliminates the long dandyline gear which tends to herd bottomfish into the net. At the start of the fishery, it was illegal to land incidentally caught fish, but in October 1957 the restriction was lifted. However, in July 1958 a 226 kg per landing limit for incidentally caught bottom fish was established. In January 1959, this fish allowance was increased to 1,360 kg upon recommendation of the Pacific Marine Fisheries Commission advisory committee.
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