FISHERY BULLETIN: VOL. 83, NO. 3 



Table 2. — Distribution of sampling effort (number 

 of tows per station) by sampling period, area, and 

 depth range, 1980-81 Penobscot Bay shrimp 

 survey.' 



Sampling 

 period 



Area 



Depth 



'See Table 1 for definitions of coded sampling 

 periods, areas, and depth ranges. 



available from stations 2 and 14. Trawling opera- 

 tions were limited to the area between Northport 

 and Islesboro in the summer of 1981, since the only 

 vessel available at that time was not equipped to 

 work elsewhere in the Bay. 



The trawl used was a semiballoon shrimp try-net 

 with a 7.6 m (25 ft) headrope and 9.5 m (31 ft) foot- 

 rope with no rollers; mesh size was 38 mm (IV2 in) in 

 the body and 31 mm (IV4 in) in the cod end. The 

 trawl was also equipped with a 12.5 mm (V2 in) liner. 

 The net was rigged on 1.2 m (4 ft) legs with ark 

 floats on the headrope and 2/0 chain on the footrope. 

 The trawl doors were hardwood, 76 x 41 cm (30 x 

 16 in), with iron bracings and a wide shoe. The net 

 was fished on a single trawl wire attached to a 30.5 

 m (100 ft) wire net bridle. All tows lasted 30 min and 

 were made at speeds varying from 1.5 to 2.5 kn. 

 Loran bearings were recorded at the beginning and 

 end of each tow, and depth was recorded either as a 

 single reading or at the beginning and end of each 

 tow. Location and depth could not be determined in 

 the summer since the vessel used then did not have 

 sonar or navigational equipment. Although three dif- 

 ferent vessels were used during the course of the 

 survey, the gear was identical and was fished the 

 same way during the entire survey. 



If catches were small (under 1 kg), the entire catch 

 was generally brought to the laboratory and frozen 

 for later analysis; otherwise, the catch was sub- 

 sampled aboard the vessel. In some cases, large 

 samples were further subsampled in the laboratory 



after they were thawed. Inasmuch as was possible, 

 all samples and subsamples were randomly selected. 

 Samples (or subsamples) of 200-900 g were sorted 

 (after removing extraneous "trash") by species ac- 

 cording to morphological characteristics described 

 by Rathbun (1929). Biological data were compiled for 

 a total of 7,259 D. leptocerus and 2,475 P. montagui; 

 numbers of P. borealis were inadequate for data 

 analysis. Each individual shrimp was sexed (male, 

 female, or transitional) using external morphological 

 characteristics for the genus Pandalics originally 

 described by Wollebaek (1908), Berkeley (1930), 

 Jagersten (1936), and Leloup (1936) and summarized 

 by Mistakidis (1957). The females were further 

 grouped as ovigerous or non-ovigerous depending on 

 whether or not the eggs had "dropped" and were 

 being carried on the pleopods; the non-ovigerous 

 females were further subdivided into two groups - 

 those which had never carried eggs before and those 

 which had - based on the presence or absence of ster- 

 nal spines. This characteristic of non-ovigerous 

 females was originally described by McCrary (1971) 

 for three pandalid species (Pandalus borealis, P. 

 goniurus, and P. hypsinotus) in Alaska. Stage I 

 females were defined as those which had not carried 

 eggs before and Stage II females as those which had; 

 there was no way to distinguish between females 

 which had carried eggs only once before and those 

 which had carried eggs more than once. Carapace 

 lengths were measured between the eye socket and 

 posterior dorsal edge of the carapace and recorded to 

 the nearest 0.1 mm. 



For each species, the numbers and lengths of 

 shrimp in each biological category (sex, with or 

 without eggs. Stage I or II) were compiled by sam- 

 pling period, geographic area, and depth range. 

 Length frequencies were expressed as numbers of 

 shrimp per 0.5 mm dorsal carapace length. Since 

 nearly all of the samples collected in areas 1-3 were 

 also collected in specific depth ranges (i.e., all 6 

 samples from area 1 were from shallow water, 16/17 

 samples from area 2 were from moderate depths, 

 and all samples from area 3 were from deep water), 

 length frequencies were presented for appropriate 

 area/depth combinations. Length-frequency data for 

 P. montagui collected in October 1981 were not 

 presented since so few individuals were captured. 



RESULTS AND DISCUSSION 



Breeding Seasons and 

 Female Sizes (Ages) at Maturity'* 



Nearly all the ovigerous female D. leptocerus were 



222 



